Correction to: Highly sensitive detection of M.SssI DNA methyltransferase activity using a personal glucose meter Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-27 Huimin Deng, Si Ying Png, Zhiqiang Gao
We should like to call your attention to the fact that Si Ying Png’s name was misspelled in the original publication: it should be Si Ying Png.
An electrochemical biosensor for the detection of Pb 2+ based on G-quadruplex DNA and gold nanoparticles Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-06-30 Shengpan Xu, Xiaojun Chen, Gang Peng, Ling Jiang, He Huang
We present a novel simple strategy for the detection of Pb2+ based on G-quadruplex DNA and gold nanoparticles. First, gold nanoparticles were chemically adsorbed onto the surface of a thiol-modified gold electrode. Subsequently, the substrate DNA1 was adsorbed onto the surfaces of the gold nanoparticles via thiol–gold bonds, so that the complementary guanine-rich DNA2 could be hybridized to the gold electrode in sequence. [Ru(NH3)6]3+ (RuHex), which can be electrostatically adsorbed onto the anionic phosphate of DNA, served as an electrochemical probe. The presence of Pb2+ can induce DNA2 to form a stable G-quadruplex and fall off the gold electrode. The amount of RuHex remaining on the electrode surface was determined by electrochemical chronocoulometry (CC). The prepared biosensor showed high sensitivity for Pb2+ with a linear range with respect to ln(cPb2+) from 0.01 to 200 nM and a low detection limit of 0.0042 nM under optimal conditions. Because of the high selectivity of the Pb2+-specific DNA2, the designed biosensor also showed low false-positive signal rates with other metal ions in real-world examples. Therefore, this strategy has the potential for practical application in environmental monitoring.
On determining the power of digital PCR experiments Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-06-30 Matthijs Vynck, Jo Vandesompele, Olivier Thas
The experimental design that will be carried out to evaluate a nucleic acid quantification hypothesis determines the cost and feasibility of digital polymerase chain reaction (digital PCR) studies. Experiment design involves the calculation of the number of technical measurement replicates and the determination of the characteristics of those replicates, and this in accordance with the capabilities of the available digital PCR platform. Available digital PCR power analyses suffer from one or more of the following limitations: narrow scope, unrealistic assumptions, no sufficient detail for replication, lack of source code and user-friendly software. Here, we discuss the nature of six parameters that affect the statistical power, i.e., desired effect size, total number of partitions, fraction of positive partitions, number of replicate measurements, between-replicate variance, and significance level. We also show to what extent these parameters affect power, and argue that careful design of experiments is needed to achieve the desired power. A web tool, dPowerCalcR, that allows interactive calculation of statistical power and optimization of the experimental design is available.
A many probes-one spot hybridization oligonucleotide microarray Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-06-22 Elena V. Kostina, Alexander N. Sinyakov, Vladimir A. Ryabinin
A variant of the hybridization oligonucleotide microarray, utilizing the principle of many probes-one spot (MPOS-microarrays), is proposed. A case study based on Orthopoxviruses (Variola, Monkeypox, and Ectromelia viruses) demonstrates a considerable increase in the fluorescence signal (up to 100-fold) when several oligonucleotide probes are printed to one spot. Moreover, the specificity of detection also increases (almost 1000-fold), allowing the use of probes that individually lack such high specificity. The optimal probes have a Tm of 32–37 °C and length of 13–15 bases. We suggest that the high specificity and sensitivity of the MPOS-microarray is a result of cooperativity of DNA binding with all probes immobilized in the spot. This variant of DNA detection can be useful for designing biosensors, tools for point-of-care (POC) diagnostics, microbial ecology, analysis of clustered regularly interspaced short palindromic repeats (CRISPR), and others.
Modulating receptor-ligand binding in biorecognition by setting surface wettability Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-17 Pilar Aragón, Patricia Noguera, María-José Bañuls, Rosa Puchades, Ángel Maquieira, Miguel Ángel González-Martínez
Modulation of support wettability used for microarray format biosensing has led to an improvement of results. Hydrophobicity of glass chips was set by derivatizing with single vinyl organosilanes of different chain length and silane mixtures. Thiol-ene photochemical linking has been used as effective chemistry for covalent anchoring of thiolated probes. Lowest unspecific binding and highest signal intensity and SNR were obtained with large hydrocarbon chain (C22) silanes or a shorter one (C10) containing fluorine atoms. SNR resulting values are improved, reaching levels higher than 1500 in some cases, when using vinyl silanes modified with 1% C10 alkyl fluorinated one, because mild hydrophobicity was achieved (water contact angle ca. 110°) for all silanes, including the short C2 and C3, thus giving rise to smaller and better defined array spots. In addition, unspecific binding of reagents and targets was totally withdrawn. Hence, good-performing surfaces for biosensing applications can be built using appropriate organosilane reagent selection, including fluorinated ones.
Rapid and sensitive SERS detection of the cytokine tumor necrosis factor alpha (tnf-α) in a magnetic bead pull-down assay with purified and highly Raman-active gold nanoparticle clusters Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-06-30 Yuming Lai, Sebastian Schlücker, Yuling Wang
Tumor necrosis factor alpha (TNF-α) is a cytokine with significance in early diagnosis of cardiovascular diseases, obesity and insulin resistance. We demonstrate the proof of concept for a rapid and sensitive detection of TNF-α using a magnetic bead pull-down assay in combination with surface-enhanced Raman scattering (SERS). The use of purified and highly SERS-active small clusters of gold nanoparticles (AuNP) provides the high sensitivity of the assay with a limit of detection of ca. 1 pg/mL. Continuous density gradient centrifugation was employed for separating the very bright silica-encapsulated AuNP dimers and trimers from the significantly weaker AuNP monomers. Negative control experiments with other cytokines (IL-6, IL-8) and bovine serum albumin (BSA) confirm the high specificity of the assay, but indicate also space for future improvements by further reducing non-specific binding between proteins and the SERS nanotags. The multiplexing potential of this SERS-based detection scheme is exemplarily demonstrated by using a set of three spectrally distinct and highly SERS-active AuNP clusters with unique spectral barcodes.
Preparation of gold nanoparticles supported on graphene oxide with flagella as the template for nonenzymatic hydrogen peroxide sensing Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-10 Chunyuan Tian, Shuang Zhang, Xuming Zhuang, Haihua Wang, Dandan Chen, Feng Luan, Tao He, Wei He, Yang Qiu
Gold nanoparticles supported on graphene oxide with flagella as the template were developed as an electrochemical sensor for the detection of hydrogen peroxide (H2O2) in serum. The flagella–Au nanoparticles composite and graphene oxide were dropped onto a glassy carbon electrode (GCE) to form a new H2O2 electrochemical sensor. The structure morphology of the prepared sensor was characterized by transmission electron microscopy (TEM), and the electrocatalytic performance towards H2O2 reduction was evaluated by cyclic voltammetry (CV) and amperometric methods. The response current of the sensor showed a good linear relationship with the concentration of H2O2 in the range of 10–1000 μM (R2 = 0.9916). The minimum detection limit of 1 μM was obtained (S/N = 3). Finally, the sensor was applied to the detection of H2O2 in serum, and the recoveries were satisfactory. As the sensor is sensitive, fast, and easy to make, it is expected to be used for rapid detection of H2O2.
Serogroup-level resolution of the “Super-7” Shiga toxin-producing Escherichia coli using nanopore single-molecule DNA sequencing Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-01-27 Adam Peritz, George C. Paoli, Chin-Yi Chen, Andrew G. Gehring
DNA sequencing and other DNA-based methods are now broadly used for detection and identification of bacterial foodborne pathogens. For the identification of foodborne bacterial pathogens, taxonomic assignments must be made to the species or even subspecies level. Long-read DNA sequencing provides finer taxonomic resolution than short-read sequencing. Here, we demonstrate the potential of long-read shotgun sequencing obtained from the Oxford Nanopore Technologies (ONT) MinION single-molecule sequencer, in combination with the Basic Local Alignment Search Tool (BLAST) with custom sequence databases, for foodborne pathogen identification. A library of mixed DNA from strains of the “Super-7” Shiga toxin-producing Escherichia coli (STEC) serogroups (O26, O45, O103, O111, O121, O145, and O157[:H7]) was sequenced using the ONT MinION resulting in 44,245 long-read sequences. The ONT MinION sequences were compared to a custom database composed of the E. coli O-antigen gene clusters. A vast majority of the sequence reads were from outside of the O-antigen cluster and did not align to any sequences in the O-antigen database. However, 58 sequences (0.13% of the total sequence reads) did align to a specific Super-7 O-antigen gene cluster, with each O-antigen cluster aligning to at least four sequence reads. BLAST analysis against a custom whole-genome database revealed that 5096 (11.5%) of the MinION sequence reads aligned to one and only one sequence in the database, of which 99.6% aligned to a sequence from a “Super-7” STEC. These results demonstrate the ability of the method to resolve STEC to the serogroup level and the potential general utility of the MinION for the detection and typing of foodborne pathogens.
Simultaneous determination of amantadine and rimantadine in feed by liquid chromatography-Qtrap mass spectrometry with information-dependent acquisition Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-04-13 Qi Jia, Dan Li, Xinlu Wang, Shuming Yang, Yongzhong Qian, Jing Qiu
A sensitive method for simultaneous determination of amantadine and rimantadine in feed was developed using an ultra-high-performance liquid chromatography-triple quadrupole linear ion trap mass spectrometry (UHPLC-Qtrap-MS) in the multiple reaction monitoring information-dependent acquisition-enhanced product ion (MRM-IDA-EPI) mode, and employing the mixed cation exchange (MCX) solid-phase extraction column as sample cleanup and amantadine-d15 and rimantadine-d4 as internal standards, respectively. Compared to traditional MRM mode, for the targeted drugs in feed simultaneously both the secondary mass spectra and MRM information can be obtained using UHPLC-Qtrap-MS with MRM-IDA-EPI mode, and thus more accurate qualitative confirmation results achieved even at lower concentration of 0.2 μg/L in acceptable purity fit values. After optimization of sample preparation, good linearities (R > 0.9994) were obtained over the concentration range from 1 to 200 μg/L for amantadine and rimantadine. The precision was validated by intra-day and inter-day, and the relative standard deviations were all within 9.61%. Mean recoveries ranged from 76.1 to 112% at spiked concentrations of 0.5–100 μg/kg in three types of feed samples, including formula feed and complex concentrated feed for pigs and premix feed for chicken. The limits of detection (LODs) and quantification (LOQs) were 0.2 and 0.5 μg/kg for both drugs, respectively. The application in real feed samples further proved the accuracy and reliability of the developed method. This method provides an important tool to detect illegal uses of amantadine and rimantadine in feed.
Ultra turrax® tube drive for the extraction of pesticides from egg and milk samples Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-19 Julia Sturm, Peter Wienhold, Thomas Frenzel, Karl Speer
The Ultra turrax® tube drive, already successfully applied for the extraction of plant materials, has also proved to be suitable for the analysis of pesticides in eggs and milk. In comparison to the matrix solid-phase dispersion (MSPD), the extraction is less time-consuming at excellent extraction efficiency. Further advantages are the flexibility of the extraction conditions with respect to the pH value and water activity. So, even strongly acidic pesticides such as phenoxy carboxylic acids can be extracted. Eighty-nine GC-amenable and 75 LC-amenable pesticides, which had been detected successfully in whole chicken eggs following MSPD extraction and further processing according to Hildmann et al., could also be analyzed with the modified method. In addition, the analysis spectrum could be expanded by 4 GC- and 37 LC-amenable substances. Of the 208 pesticides tested, 205 substances could be detected in whole chicken eggs. Similar excellent results were achieved for the milk matrix. Furthermore, the modified extraction method allows a determination of the fat content from the same analysis approach.
In-house validation of a rapid and efficient procedure for simultaneous determination of ergot alkaloids and other mycotoxins in wheat and maize Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-03-24 Natalia Arroyo-Manzanares, Karl De Ruyck, Valdet Uka, Laura Gámiz-Gracia, Ana M. García-Campaña, Sarah De Saeger, José Diana Di Mavungu
A fundamental step in addressing the global problem of mycotoxins is the development of highly sensitive, multi-class extraction and detection methods. This constitutes a field of research that has in recent years enjoyed a steady advance. Such methods, generally based on liquid chromatography coupled to mass spectrometry, are widely reported successfully detecting various mycotoxins in different food and feed samples. In this work, an innovative approach to multi-class mycotoxin control is proposed, offering specific advantages: a broader inclusion of more mycotoxin classes, robust and thorough extraction for all target compounds despite their varied chemical properties, and determination of all analytes from a single injection. The method involved the extraction and quantification of the main mycotoxins produced by Aspergillus, Fusarium, and Penicillium fungi, as well as their reported derivatives, together with 12 other compounds most commonly produced by Claviceps purpurea. The popularly reported QuEChERS technique has been reduced to a simple “salting-out liquid-liquid extraction” (SO-LLE) to obtain the most efficient extraction of the aforementioned mycotoxin classes in a very short time. This is in particular extremely important in ensuring correct determination of individual ergot alkaloids, for which short and robust sample preparation as well as short analytical sequences were key for minimizing the epimerization during analysis. The analyses of wheat and maize samples were performed using ultra-high performance liquid chromatography coupled with tandem mass spectrometry. Matrix-matched calibration curves were established and limits of quantification were below the maximum levels established by the EU regulation. The precision (repeatability and intermediate precision) was lower than 13% in all cases and recoveries ranged between 60 and 98% in maize and between 62 and 103% in wheat, fulfilling the current legislation. The method was applied to study the co-occurrence of these mycotoxins in wheat (n = 13) and maize (n = 15) samples from six European countries. A successful quantification of 23 different mycotoxins, from all major classes, in 85% of wheat and 93% of maize samples was achieved.
Elucidation of non-intentionally added substances migrating from polyester-polyurethane lacquers using automated LC-HRMS data processing Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-03-08 Elsa Omer, Ronan Cariou, Gérald Remaud, Yann Guitton, Hélène Germon, Paul Hill, Gaud Dervilly-Pinel, Bruno Le Bizec
An untargeted strategy aiming at identifying non-intentionally added substances (NIAS) migrating from coatings was developed. This innovative approach was applied to two polyester-polyurethane lacquers, for which suppliers previously provided the identity of the monomers involved. Lacquers were extracted with acetonitrile and analyzed by liquid chromatography-high resolution mass spectrometry (LC-HRMS). Data, acquired in the full scan mode, were processed using an open-source R-environment (xcms and CAMERA packages) to list the detected features and deconvolute them in groups related to individual compounds. The most intense groups, accounting for more than 85% of cumulated feature intensities, were then investigated. A homemade database, populated with predicted polyester oligomer combinations from a relevant selection of diols and diacids, enabled highlighting the presence of 14 and 17 cyclic predicted polyester oligomers in the two lacquers, including three mutual combinations explained by common known monomers. Combination hypotheses were strengthened by chromatographic considerations and by the investigation of fragmentation patterns. Regarding unpredicted migrating substances, four monomers were hypothesised to explain several polyester or caprolactam oligomer series. Finally, considering both predicted and tentatively elucidated unpredicted oligomers, it was possible to assign hypotheses to features representing up to 82% and 90% of the cumulated intensities in the two lacquers, plus 9% and 3% (respectively) originating from the procedural blank.
Pesticide analysis by pulsed flow modulation GCxGC-MS with Cold EI—an alternative to GC-MS-MS Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2017-12-13 Uri Keshet, Paulina Goldshlag, Aviv Amirav
We explored the use of pulsed flow modulation (PFM) two-dimensional comprehensive gas chromatography (GCxGC) mass spectrometry with supersonic molecular beams (SMB) (also named Cold electron ionization (EI)) for achieving universal pesticide analysis in agricultural products. The use of GCxGC serves as an alternative to MS-MS in the needed reduction of matrix interference while enabling full-scan MS operation for universal pesticide analysis with reduced number of false negatives. Matrix interference is further reduced with Cold EI in view of the enhancement of the molecular ions. Pulsed flow modulation is a simple GCxGC modulator that does not consume cryogenic gases while providing tuneable second GCxGC column injection time for enabling the use of quadrupole-based mass spectrometry regardless its limited scanning speed. PFM-GCxGC-MS with Cold EI combines improved separation of GCxGC with Cold EI benefits of tailing-free ultra-fast ion source response time and enhanced molecular ions for the provision of increased sample identification information and reduced matrix interference. Consequently, PFM GCxGC-MS with Cold EI also improved NIST library identification probabilities of the spiked pesticides. PFM GCxGC is further characterized by largely increased second column sample and matrix capacity that as a result performs much better than thermal modulation GCxGC-MS with standard EI in the suppression of matrix interference. In a comparison with standard GC-MS, we measured with PFM GCxGC-MS with Cold EI an average total ion count matrix interference reduction factor of 32 for 12 pesticides in two matrices of baby leaves mixture and lettuce. In addition, Cold EI further increases the range of pesticides amenable for GC-MS analysis and its response is relatively uniform hence with it the need for pesticides specific calibration is reduced.
Speciation analysis of arsenic in seafood and seaweed: Part II—single laboratory validation of method Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-02-23 Mesay Mulugeta Wolle, Sean D. Conklin
Single laboratory validation of a method for arsenic speciation analysis in seafood and seaweed is presented. The method is based on stepwise extraction of water-soluble and non-polar arsenic with hot water and a mixture of dichloromethane and methanol, respectively. While the water-soluble arsenicals were speciated by anion and cation exchange liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS), the non-polar arsenicals were collectively determined by ICP-MS after digestion in acid. The performance characteristics and broad application of the method were evaluated by analyzing eight commercial samples (cod, haddock, mackerel, crab, shrimp, geoduck clam, oyster, and kombu) and four reference materials (fish protein (DORM-4), lobster hepatopancreas (TORT-3), mussel tissue (SRM 2976), and hijiki seaweed (CRM 7405-a)) representing finfish, crustaceans, molluscs, and seaweed. Matrices spiked at three levels in duplicates were also analyzed. The stepwise extraction provided 76–106% extraction of the total arsenic from the test materials. The method demonstrated satisfactory repeatability for analysis of replicate extracts prepared over several days. The accuracy of the method was evaluated by analyzing reference materials certified for both total arsenic and a few arsenicals; the experimental results were 90–105% of the certified values. Comparison between the total water-soluble arsenic and the sum of the concentrations of the chromatographed species gave 80–92% mass balance. While spike recoveries of most arsenicals were in the acceptance range set by CODEX, a few species spiked into cod, haddock, and shrimp were poorly recovered due to transformation to other forms. After thorough investigations, strategies were devised to improve the recoveries of these species by averting their transformations. Limits of quantification (LOQ) for the extraction and quantification of 16 arsenicals using the current method were in the range 6–16 ng g−1 arsenic.
Speciation analysis of arsenic in seafood and seaweed: Part I—evaluation and optimization of methods Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-02-17 Mesay Mulugeta Wolle, Sean D. Conklin
Several extraction and chromatographic methods were evaluated to identify optimum conditions for arsenic speciation analysis in seafood and seaweed. The extraction systems, which include aqueous, aqueous-organic, acidic, basic, and enzymatic solutions, were examined for their efficiency in extracting arsenic from finfish, crustaceans, molluscs, and seaweed keeping the chemical forms of the native arsenicals intact. While dilute solutions of nitric acid, hydrochloric acid, and tetramethylammonium hydroxide (TMAH) extract high fractions of arsenic from most of the matrices, the extractants oxidized arsenite (As3+) to arsenate (As5+) and converted some arsenosugars and non-polar arsenicals to known and/or unknown forms. Hot water (90 °C) effectively maintained the integrity of the native arsenic species and enabled analysis of the extracts with no further manipulation than filtration and dilution. Stepwise extraction of water-soluble and non-polar arsenic with hot water and a mixture of dichloromethane and methanol, respectively, resulted in sufficiently quantitative (> 75%) arsenic extraction from seafood and seaweed. Anion and cation exchange chromatographic methods were optimized for separation and quantitation of the arsenicals extracted into hot water. The non-polar arsenicals were collectively determined after digesting the extract in acid. The application of the optimum extraction and chromatographic conditions was demonstrated by analyzing certified reference materials of tuna fish tissue (BCR 627), lobster hepatopancreas (TORT-2) and oyster tissue (SRM 1566b), and a sample of hijiki seaweed. For all the matrices, good agreement (80–92%) was found between the total water-soluble arsenic and the sum of the concentrations of the chromatographed species. Limits of quantification (LOQ) were in the range 4–11 ng g−1 for 16 arsenicals.
Non-targeted analysis of unexpected food contaminants using LC-HRMS Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-03-29 Marco Kunzelmann, Martin Winter, Magnus Åberg, Karl-Erik Hellenäs, Johan Rosén
A non-target analysis method for unexpected contaminants in food is described. Many current methods referred to as “non-target” are capable of detecting hundreds or even thousands of contaminants. However, they will typically still miss all other possible contaminants. Instead, a metabolomics approach might be used to obtain “true non-target” analysis. In the present work, such a method was optimized for improved detection capability at low concentrations. The method was evaluated using 19 chemically diverse model compounds spiked into milk samples to mimic unknown contamination. Other milk samples were used as reference samples. All samples were analyzed with UHPLC-TOF-MS (ultra-high-performance liquid chromatography time-of-flight mass spectrometry), using reversed-phase chromatography and electrospray ionization in positive mode. Data evaluation was performed by the software TracMass 2. No target lists of specific compounds were used to search for the contaminants. Instead, the software was used to sort out all features only occurring in the spiked sample data, i.e., the workflow resembled a metabolomics approach. Procedures for chemical identification of peaks were outside the scope of the study. Method, study design, and settings in the software were optimized to minimize manual evaluation and faulty or irrelevant hits and to maximize hit rate of the spiked compounds. A practical detection limit was established at 25 μg/kg. At this concentration, most compounds (17 out of 19) were detected as intact precursor ions, as fragments or as adducts. Only 2 irrelevant hits, probably natural compounds, were obtained. Limitations and possible practical use of the approach are discussed.
Detection of nanoplastics in food by asymmetric flow field-flow fractionation coupled to multi-angle light scattering: possibilities, challenges and analytical limitations Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-02-06 Manuel Correia, Katrin Loeschner
We tested the suitability of asymmetric flow field-flow fractionation (AF4) coupled to multi-angle light scattering (MALS) for detection of nanoplastics in fish. A homogenized fish sample was spiked with 100 nm polystyrene nanoparticles (PSNPs) (1.3 mg/g fish). Two sample preparation strategies were tested: acid digestion and enzymatic digestion with proteinase K. Both procedures were found suitable for degradation of the organic matrix. However, acid digestion resulted in large PSNPs aggregates/agglomerates (> 1 μm). The presence of large particulates was not observed after enzymatic digestion, and consequently it was chosen as a sample preparation method. The results demonstrated that it was possible to use AF4 for separating the PSNPs from the digested fish and to determine their size by MALS. The PSNPs could be easily detected by following their light scattering (LS) signal with a limit of detection of 52 μg/g fish. The AF4-MALS method could also be exploited for another type of nanoplastics in solution, namely polyethylene (PE). However, it was not possible to detect the PE particles in fish, due to the presence of an elevated LS background. Our results demonstrate that an analytical method developed for a certain type of nanoplastics may not be directly applicable to other types of nanoplastics and may require further adjustment. This work describes for the first time the detection of nanoplastics in a food matrix by AF4-MALS. Despite the current limitations, this is a promising methodology for detecting nanoplastics in food and in experimental studies (e.g., toxicity tests, uptake studies).
Analysis of unauthorized Sudan dyes in food by high-performance thin-layer chromatography Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-03-07 Wolfgang Schwack, Elodie Pellissier, Gertrud Morlock
Food authenticity and food safety are of high importance to organizations as well as to the food industry to ensure an accurate labeling of food products. Respective analytical methods should provide a fast screening and a reliable cost-efficient quantitation. HPTLC was pointed out as key analytical technique in this field. A new HPTLC method applying caffeine-impregnated silica gel plates was developed for eight most frequently found fat-soluble azo dyes unauthorizedly added to spices, spice mixtures, pastes, sauces, and palm oils. A simple post-chromatographic UV irradiation provided an effective sample cleanup, which took 4 min for up to 46 samples in parallel. The method was trimmed to enable 23 simultaneous separations within 20 min for quantitation or 46 separations within 5 min for screening. Linear (4–40 ng/band) or polynomial (10–200 ng/band) calibrations of the eight azo dyes revealed high correlation coefficients and low standard deviations. Limits of detection and quantification were determined to be 2–3 and 6–9 ng/zone, respectively. After an easy sample extraction, recoveries of 70–120% were obtained from chili, paprika, and curcuma powder as well as from chili sauce, curry paste, and palm oil spiked at low (mainly 25–50 mg/kg) and high levels (150–300 mg/kg). For unequivocal identification, the compound in a suspect zone was eluted via a column into the mass spectrometer. This resulted in the hyphenation HPTLC-vis-HPLC-DAD-ESI-MS.
Further improvements in pesticide residue analysis in food by applying gas chromatography triple quadrupole mass spectrometry (GC-QqQ-MS/MS) technologies Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2017-11-14 Elena Hakme, Ana Lozano, Samanta Uclés, Amadeo R. Fernández-Alba
Nowadays, the control of pesticide residues in food is well established. The capacity of triple quadrupole technology to satisfy the current food regulations has been demonstrated. However, the permanent high demand of consumers for more sensitive and faster testing is driving the development of improved analytical methodologies that increase the performances of sensitivity and robustness and reduce the analysis time. In this work, the feasibility of decreasing the run time to 12.4 min by modifying the oven temperature program, for a multiresidue method covering 203 pesticides, was evaluated. Satisfactory sensitivity results were achieved by reaching a limit of quantitation of 2 μg kg−1 for a great variety of fruits and vegetables. The validated method based on updated GC-QqQ-MS/MS has confirmed the abovementioned challenges with adequate robustness by its application to routine analyses for 69 real samples. The proposed method can represent great benefit for laboratories as it allows increasing samples throughput. It is also very useful for risk assessment studies, where the needs of low reporting limits and very wide analytical scope are necessary.
Analysis of a variety of inorganic and organic additives in food products by ion-pairing liquid chromatography coupled to high-resolution mass spectrometry Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-03-05 Anton Kaufmann, Mirjam Widmer, Kathryn Maden, Patrick Butcher, Stephan Walker
A reversed-phase ion-pairing chromatographic method was developed for the detection and quantification of inorganic and organic anionic food additives. A single-stage high-resolution mass spectrometer (orbitrap ion trap, Orbitrap) was used to detect the accurate masses of the unfragmented analyte ions. The developed ion-pairing chromatography method was based on a dibutylamine/hexafluoro-2-propanol buffer. Dibutylamine can be charged to serve as a chromatographic ion-pairing agent. This ensures sufficient retention of inorganic and organic anions. Yet, unlike quaternary amines, it can be de-charged in the electrospray to prevent the formation of neutral analyte ion-pairing agent adducts. This process is significantly facilitated by the added hexafluoro-2-propanol. This approach permits the sensitive detection and quantification of additives like nitrate and mono-, di-, and triphosphate as well as citric acid, a number of artificial sweeteners like cyclamate and aspartame, flavor enhancers like glutamate, and preservatives like sorbic acid. This is a major advantage, since the currently used analytical methods as utilized in food safety laboratories are only capable in monitoring a few compounds or a particular category of food additives.
Identification of acetylated derivatives of zearalenone as novel plant metabolites by high-resolution mass spectrometry Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-04-30 Laura Righetti, Luca Dellafiora, Daniele Cavanna, Enrico Rolli, Gianni Galaverna, Renato Bruni, Michele Suman, Chiara Dall’Asta
Zearalenone (ZEN) major biotransformation pathways described so far are based on glycosylation and sulfation, although acetylation of trichothecenes has been reported as well. We investigated herein the ZEN acetylation metabolism route in micropropagated durum wheat leaf, artificially contaminated with ZEN. We report the first experimental evidence of the formation of novel ZEN acetylated forms in wheat, attached both to the aglycone backbone as well as on the glucose moiety. Thanks to the advantages provided by high-resolution mass spectrometry, identification and structure annotation of 20 metabolites was achieved. In addition, a preliminary assessment of the toxicity of the annotated metabolites was performed in silico focusing on the toxicodynamic of ZEN group toxicity. All the metabolites showed a worse fitting within the estrogen receptor pocket in comparison with ZEN. Nevertheless, possible hydrolysis to the respective parent compounds (i.e., ZEN) may raise concern from the health perspective because these are well-known xenoestrogens. These results further enrich the biotransformation profile of ZEN, providing a helpful reference for assessing the risks to animals and humans.
Tris(2,2′-bipyridyl)ruthenium(II) electrochemiluminescent determination of ethyl formate Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-07 Tadesse Haile Fereja, Shimeles Addisu Kitte, Dmytro Snizhko, Liming Qi, Anaclet Nsabimana, Zhongyuan Liu, Guobao Xu
Ethyl formate is extensively used as food flavor, fungicide, and larvicide. It naturally exists in coffee, fruits, honey, brandy, and rum as well as dust clouds in an interstellar space of the Milky Way galaxy. Herein, its electrochemiluminescence (ECL) property has been firstly investigated. It shows intense ECL in reaction with Ru(bpy)32+ as luminophore, and thus a rapid and sensitive detection method for ethyl formate is proposed. Effects of pH, working potential, scan rate, and concentration of Ru(bpy)32+ were studied. ECL spectrum analysis was used to reveal the reaction mechanism. At the optimized experimental conditions, a linear relationship between ECL intensities and concentrations of ethyl formate is observed from 3.0 μM to 1.0 mM (R2 = 0.997). The limit of detection for ethyl formate is 0.7 μM (S/N = 3). The relative standard deviation with 1.0 mM concentration of ethyl formate for nine analyses is 2.7%. A 101.20–102.10% recovery was obtained in a real samples analysis.
One-step synthesized flower-like materials used for sensitively detecting amyloid precursor protein Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-06 Chengke Wang, Rong Tan, Qingqing Wang
In this paper, we developed a new method to detect Alzheimer’s disease (AD)-related amyloid precursor protein (APP). A composite material containing horseradish peroxidase (HRP), APP antibody, and Cu3(PO4)2 was synthesized as the biosensor by co-precipitation method. In this competitive immunoassay, APP was first conjugated onto the microplate surface with the help of poly-L-lysine as the coating reagent; the composite materials were then attached onto the microplate through the interaction of APP and antibody; the HRP can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) and formed colored species. Therefore, the more APP in the detection solution (free form), the less composite material was combined with the immobilized APP on the microplate, resulting in the production of less colored TMB species. A series of detection parameters were studied, such as the composite material synthesis process, the concentration, and reaction time of different compounds. Our method has higher sensitivity compared with the similar immunoassay without using composite materials (the limits of detection are 0.3 and 3 ng/mL, respectively), and can be used for real samples (human serum) detection. The detection results using our method are consistent with the ELISA results, which is useful for the AD detection.
Where are modern flow techniques heading to? Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-06 Burkhard Horstkotte, Manuel Miró, Petr Solich
This article aims to provide an overview on the transition from earlier laboratory automation using analytical flow approaches toward today’s applications of flow methodologies, recent developments, and future trends. The article is directed to flow practitioners while serving as a valuable reference to newcomers in the field in providing insight into flow techniques and conceptual differences in operation across the distinct flow generations. In the focus are the recently developed and complementary techniques Lab-On-Valve and Lab-In-Syringe. In the following, a brief comparison of the different application niches and contributions of flow techniques to past and modern analytical chemistry is given, including (i) the development of sample pretreatment approaches, (ii) the potential applicability for in-situ/on-site monitoring of environmental compartments or technical processes, (iii) the ability of miniaturization of laboratory chemistry, (iv) the unique advantages for implementation of kinetic assays, and finally (v) the beneficial online coupling with scanning or separation analytical techniques. We also give a critical comparison to alternative approaches for automation based on autosamplers and robotic systems. Finally, an outlook on future applications and developments including 3D prototyping and specific needs for further improvements is given.
Application of polyethyleneimine-modified attapulgite for the solid-phase extraction of chlorophenols at trace levels in environmental water samples Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-04 Mengsa Chai, Yihui Chen, Rongrong Xuan, Junfeng Ma, Zhenfeng Jin, Tingting Wang, Dan Qiu, Lihua Zhang, Yukui Zhang
A polyethyleneimine (PEI)-modified attapulgite was employed as a new adsorbent for solid-phase extraction (SPE) of chlorophenols (CPs) from environmental water samples. Key factors pivotal to extraction efficiency, such as organic additive, pH, salt, sample loading volume, elution volume, and sample loading flow rate, were investigated. The maximum adsorption capacity of CPs reached 38 mg/g, and the adsorption behavior could be described with the Langmuir isotherm model. The developed SPE procedure was then tested on river water samples. Of this cartridge, 0.4 g could be used to treat up to 100 mL of the water sample, with high recoveries achieved. The limit of detection (S/N = 3) and the limit of quantification (S/N = 10) were in range of 0.08–0.56 and 0.27–1.88 ng/mL, respectively. The mean recoveries of CPs spiked in river water samples ranged from 84.4 to 96.8% with relative standard deviations for the intra-day and inter-day less than 6.30%. The developed SPE method exhibited high sensitivity, high selectivity, excellent accuracy, and good repeatability to the analysis of trace CPs in complicated aqueous matrices.
Clustering-based preprocessing method for lipidomic data analysis: application for the evolution of newborn skin surface lipids from birth until 6 months Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-04 Rime Michael-Jubeli, Ali Tfayli, Caroline Baudouin, Jean Bleton, Dominique Bertrand, Arlette Baillet-Guffroy
After life in utero and birth, the skin is submitted to an important process of adaptation to a relatively dry gaseous environment. Skin surface lipids (SSLs) contribute actively to the protection of the skin barrier. Within this context, our objective was to study the evolution of each lipid compound during the postnatal period. SSLs were collected from six newborns a few days after birth until the age of 6 months. Seventy samples were analyzed using high-temperature gas chromatography coupled to mass spectrometry (HT-GC/MS). The use of separative techniques coupled to mass spectrometry for the analysis of samples containing complex mixtures of lipids generates a large volume of data which renders the results interpretation very difficult. In this study, we propose a new approach to handle the raw data, a clustering-based preprocessing method (CB-PPM), in order to achieve (1) volume reduction of data provided by each chromatogram without loss of information, (2) alignment of time retention shift between different runs, (3) clustering of mass spectra of the same molecule in one qualitative group, (4) and integration of all data into a single matrix to be explored by chemometric tools. This approach allowed us to gather data variations in 256 qualitative groups and therefore enabled us to highlight the variation of compounds including those of low intensity. Moreover, the representation of all data gathered in one matrix rendered reading of the results rapid and efficient. Thus, using this approach, we have demonstrated an increase of cholesterol esterification with epidermal fatty acids (C20 to C25) with age. This epidermis participation in SSL production at a molecular level in the first period of life has not been previously shown. These data can be very interesting for the development and improvement of products destined for the protection of infant skin.
Development of a hydrophilic interaction high-performance liquid chromatography method for the determination of glycine in formulations of therapeutic immunoglobulins Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-02 Olga Rounova, Peter Demin, Mikhail Korotkov, Victoriya Malkova, Olga Ustinnikova
In the study presented, a simple analytical method for the direct determination of glycine in immunoglobulins by hydrophilic interaction liquid chromatography was developed. The HPLC separation was performed using a SeQuant ZIC-HILIC column (250 mm × 4.6 mm i.d, 5 μm) with the isocratic mobile phase consisting of ammonium formate (20 mM) and acetonitrile (30:70, v/v), and the flow rate set at 0.8 mL/min. UV detection was carried out at a wavelength of 210 nm. The procedure was validated for specificity, precision, linearity, accuracy, limit of detection, limit of quantitation, and robustness. The calibration curve was found to be linear within the concentration range of 1.2–3.6 mg/mL. RSD values for intra-day and inter-day precision were in the range of 0.66 to 1.84%. The limit of quantification and limit of detection were 0.10 mg/mL and 0.03 mg/mL, respectively. The developed chromatographic method was applied for the glycine analysis in various immunoglobulins.
Chemometrics in analytical chemistry—part II: modeling, validation, and applications Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-02 Richard G. Brereton, Jeroen Jansen, João Lopes, Federico Marini, Alexey Pomerantsev, Oxana Rodionova, Jean Michel Roger, Beata Walczak, Romà Tauler
The contribution of chemometrics to important stages throughout the entire analytical process such as experimental design, sampling, and explorative data analysis, including data pretreatment and fusion, was described in the first part of the tutorial “Chemometrics in analytical chemistry.” This is the second part of a tutorial article on chemometrics which is devoted to the supervised modeling of multivariate chemical data, i.e., to the building of calibration and discrimination models, their quantitative validation, and their successful applications in different scientific fields. This tutorial provides an overview of the popularity of chemometrics in analytical chemistry.
Flow field-flow fractionation for hydrodynamic diameter estimation of gold nanoparticles with various types of surface coatings Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-02 Rattaporn Saenmuangchin, Atitaya Siripinyanond
Flow field-flow fractionation (FlFFF) with inductively coupled plasma mass spectrometric (ICP-MS) detection was applied for estimating the hydrodynamic diameter of gold nanoparticles (AuNPs). Hydrodynamic diameters of AuNPs of the same core diameter but with different surface coatings were different because the coating agents and their properties were different. The challenge of this work is due to the fact that AuNPs with various types of surface coatings exhibited different interactions in the FlFFF channel, leading to different retention behaviors. Therefore, we are interested in finding suitable FlFFF conditions for estimating the hydrodynamic diameter of AuNPs with various types of electrostatic stabilizing agents [tannic acid (TA) and citrate (CT)] and steric stabilizing agents [polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and branched polyethylene imine (BPEI)]. Different types of carrier liquids (DI water, 0.02% FL-70, 0.05% SDS, and 30 mM Tris buffer) and membrane materials [regenerated cellulose (RC) and polyethersulfone (PES) membranes] were investigated. Generally, FlFFF was applied for size characterization of nanoparticles based on FlFFF theory but the interactions between AuNPs and membrane affected the retention and the experimentally obtained hydrodynamic diameters of AuNPs from the FlFFF system. With DI water as a carrier liquid with RC or PES membranes, the hydrodynamic diameters of negatively charged particles (TA-, CT-, PVP-, and PEG-stabilized AuNPs) from FlFFF corresponded well with the hydrodynamic diameters from dynamic light scattering (DLS). Interestingly, it was possible to estimate hydrodynamic diameters of AuNPs in the mixture by using FlFFF whereas it was not possible with the use of DLS within the size range studied. This work summarized the possible interactions between AuNPs with various coating agents and membrane materials in different carrier liquids to give guidelines on the suitable conditions of FlFFF for further applications on AuNP hydrodynamic diameter estimation.
Digital microfluidic immobilized cytochrome P450 reactors with integrated inkjet-printed microheaters for droplet-based drug metabolism research Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-02 Gowtham Sathyanarayanan, Markus Haapala, Iiro Kiiski, Tiina Sikanen
We report the development and characterization of digital microfluidic (DMF) immobilized enzyme reactors (IMERs) for studying cytochrome P450 (CYP)-mediated drug metabolism on droplet scale. The on-chip IMERs consist of porous polymer (thiol-ene) monolith plugs prepared in situ by photopolymerization and functionalized with recombinant CYP1A1 isoforms (an important detoxification route for many drugs and other xenobiotics). The DMF devices also incorporate inexpensive, inkjet-printed microheaters for on-demand regio-specific heating of the IMERs to physiological temperature, which is crucial for maintaining the activity of the temperature-sensitive CYP reaction. For on-chip monitoring of the CYP activity, the DMF devices were combined with a commercial well-plate reader, and a custom fluorescence quantification method was developed for detection of the chosen CYP1A1 model activity (ethoxyresorufin-O-deethylation). The reproducibility of the developed assay was examined with the help of ten parallel CYP-IMERs. All CYP-IMERs provided statistically significant difference (in fluorescence response) compared to any of the negative controls (including room-temperature reactions). The average (n = 10) turnover rate was 20.3 ± 9.0 fmol resorufin per minute. Via parallelization, the concept of the droplet-based CYP-IMER developed in this study provides a viable approach to rapid and low-cost prediction of the metabolic clearance of new chemical entities in vitro.
Nicking-enhanced rolling circle amplification for sensitive fluorescent detection of cancer-related microRNAs Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-08-01 Zhihua Gao, Chengwei Wu, Sha Lv, Cong Wang, Nan Zhang, Shuai Xiao, Ying Han, Huo Xu, Yan Zhang, Feng Li, Jianxin Lyu, Zhifa Shen
In this study, a biosensing system based on nicking-enhanced rolling circle amplification (N-RCA) was proposed for the highly sensitive detection of cancer-related let-7a microRNA (miRNA). The sensing system consists of a padlock probe (PP), which contains a target recognition sequence and two binding sites for nicking endonuclease (NEase), and molecular beacon (MB) as reporting molecule. Upon hybridization with let-7a, the PP can be circularized by ligase. Then, the miRNA acted as polymerization primer to initiate rolling circle amplification (RCA). With the assistance of NEase, RCA products can be nicked on the cyclized PP and are displaced during the subsequent duplication process, generating numerous nicked fragments (NFs). These NFs not only induce another RCA reaction but also open the molecular beacons (MBs) via hybridization, leading to significantly amplified fluorescence signal. Under the optimized conditions, this method exhibits high sensitivity toward target miRNA let-7a with a detection limit of as low as 10 pM, a dynamic range of three orders of magnitude is achieved, and its family member is easily distinguished even with only one mismatched base. Meanwhile, it displays good recovery and satisfactory reproducibility in fetal bovine serum (FBS). Therefore, these merits endow the newly proposed N-RCA strategy with powerful implications for miRNA detection.
Cataluminescence sensing of carbon disulfide based on CeO 2 hierarchical hollow microspheres Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-06-25 Pingyang Cai, Xiaofeng Yi, Hongjie Song, Yi Lv
Material morphology-dependent cataluminescence (CTL) sensing characteristic and application are presented in this work. Hierarchical hollow microspheres CeO2 were synthesized via the hydrothermal reaction of glucose and N, N-dimethyl-formamide (Glu-DMF). SEM, XRD, TEM, HRTEM and BET were used to characterize the prepared CeO2 materials. Compared with CeO2 cubics (CeO2 Cubs), CeO2 hierarchical hollow microspheres (CeO2 HMs) show an enhanced CTL response to carbon disulfide. The response and recovery times of CeO2 HMs-based CTL sensor towards carbon disulfide are about 8 s and 20 s, respectively. CeO2 HMs exhibits a linear CTL response to carbon disulfide in the concentration range of 0.50~10 μg•mL-1 with an excellent sensitivity and selectivity. These results suggest that CeO2 HMs will be a highly promising CTL sensing material for the detection and monitoring carbon disulfide.
A colorimetric assay of DNA methyltransferase activity based on peroxidase mimicking of DNA template Ag/Pt bimetallic nanoclusters Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-06-22 Hanie Ahmadzade Kermani, Morteza Hosseini, Andrea Miti, Mehdi Dadmehr, Giampaolo Zuccheri, Saman Hosseinkhani, Mohammad Reza Ganjali
DNA methylation catalyzed by DNA methyl transferase (MTase) is a significant epigenetic process for modulating gene expression. Abnormal levels of DNA MTase enzyme have been regarded as a cancer biomarker or a sign of bacterial diseases. We developed a novel colorimetric method to assay M.SssI MTase activity employing peroxidase-like activity of DNA template Ag/Pt NCs without using restriction enzymes. Based on inhibiting the peroxidase reaction that occurred in the TMB-H2O2 system, in the presence of MTase, a highly sensitive and selective colorimetric biosensor was fabricated with a detection limit (LOD) of 0.05 U/mL and a linear range from 0.5 to 10 U/mL. The changes in absorption intensity were monitored to quantify the M.SssI activity. This strategy had a high selectivity over other proteins. Furthermore, it is also demonstrated that this method can be used for the evaluation and screening of inhibitors for DNA MTase.
Hydrophilic interaction liquid chromatography in the separation of glycopeptides and their isomers Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-05-28 Petr Kozlik, Radoslav Goldman, Miloslav Sanda
The analysis of intact glycopeptides is a challenge because of the structural variety of the complex conjugates. In this work, we used separation involving hydrophilic interaction liquid chromatography using a superficially porous particle HALO® penta-HILIC column with tandem mass spectrometric detection for the analysis of N-glycopeptides of hemopexin. We tested the effect of the mobile phase composition on retention and separation of the glycopeptides. The results indicated that the retention of the glycopeptides was the combination of partitioning and adsorption processes. Under the optimized conditions, our HILIC method showed the ability to efficiently separate the glycoforms of the same peptide backbone including separation of the isobaric glycoforms. We achieved efficient separation of core and outer arm linked fucose of bi-antennary and tri-antennary glycoforms of the SWPAVGNCSSALR peptide and bi-antennary glycoform of the ALPQPQNVTSLLGCTH peptide, respectively. Moreover, we demonstrated the separation of antennary position of sialic acid linked via α2-6 linkage of the monosialylated glycopeptides. Glycopeptide isomers are often differentially associated with various biological processes. Therefore, chromatographic separation of the species without the need for an extensive sample preparation appears attractive for their identification, characterization, and reliable quantification.
Proteins and antibodies in serum, plasma, and whole blood—size characterization using asymmetrical flow field-flow fractionation (AF4) Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-05-29 Mats Leeman, Jaeyeong Choi, Sebastian Hansson, Matilda Ulmius Storm, Lars Nilsson
The analysis of aggregates of therapeutic proteins is crucial in order to ensure efficacy and patient safety. Typically, the analysis is performed in the finished formulation to ensure that aggregates are not present. An important question is, however, what happens to therapeutic proteins, with regard to oligomerization and aggregation, after they have been administrated (i.e., in the blood). In this paper, the separation of whole blood, plasma, and serum is shown using asymmetric flow field-flow fractionation (AF4) with a minimum of sample pre-treatment. Furthermore, the analysis and size characterization of a fluorescent antibody in blood plasma using AF4 are demonstrated. The results show the suitability and strength of AF4 for blood analysis and open new important routes for the analysis and characterization of therapeutic proteins in the blood.
LC/MS analysis of vitamin D metabolites by dielectric barrier discharge ionization and a comparison with electrospray ionization and atmospheric pressure chemical ionization Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-05-26 Sebastian Hagenhoff, Heiko Hayen
Serum vitamin D metabolite levels are of interest as biomarkers for vitamin D status, which has influence on numerous body functions and pathologies. The determination of vitamin D metabolite levels by liquid chromatography/mass spectrometry (LC/MS) is challenging due to their low concentrations and relatively low ionization efficiencies. Three ionization sources, dielectric barrier discharge ionization (DBDI), atmospheric pressure chemical ionization (APCI), and electrospray ionization (ESI), were compared regarding achievable limits of detection and occurring matrix effects. The latter were mainly caused by phospholipids. Therefore, in addition to a conventional solid phase extraction (SPE) stationary phase, a material for selective removal of phospholipids was examined. The selective removal of phospholipids significantly reduced observed matrix effects, especially when ESI was applied. Achievable limits of detection and observed matrix effects were lowest for APCI and with some limitations, also for DBDI.
Highly selective and ratiometric fluorescent nanoprobe for the detection of cysteine and its application in test strips Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-05-11 Fengyang Wang, Yingying Zhu, Jie Xu, Zhiai Xu, Guiying Cheng, Wen Zhang
Cysteine (Cys) is a bithiol that plays a vital role in many physiological processes. However, it is difficult to discriminate Cys from homocysteine (Hcy) and glutathione (GSH), due to their similar chemical structures and reactivity. Herein, we have developed a polymeric nanoprobe, nanoHFA, for ratiometric, highly selective, and sensitive detection of Cys based on 7-hydroxycoumarin-3-carboxylic acid (HC) and fluorescein isothiocyanate (FITC)-acrylate (FITC-A) group-functionalized lipopolymer DSPE-PEG. The probe nanoHFA showed a strong fluorescence emission peak centered at 450 nm attributed to HC and a weak fluorescence emission peak centered at 520 nm due to the photoinduced electron transfer (PET) process of FITC induced by acrylate group. In the presence of Cys, the fluorescence signal at 520 nm could be lit up and the ratio of F520nm/F450nm showed a good linear relationship in the range of 5–60 μM with a low detection limit of 0.37 μM. The probe also displayed excellent water solubility and high selectivity to Cys over other biothiols such as Hcy and GSH. Moreover, we further used probe nanoHFA to detect Cu2+ ions in the range of 100–550 nM with a detection limit of 77 nM. The nanoprobe was successfully applied for the quantitative detection of Cys in fetal bovine serum, and fluorescent strips were developed for facile and visual detection of Cys and Cu2+ ions.
An enzyme-free homogenous electrochemical assay for sensitive detection of the plasmid-mediated colistin resistance gene mcr-1 Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-05-22 Bo Li, Zhixin Chai, Xiaohui Yan, Chunchen Liu, Bo Situ, Ye Zhang, Weilun Pan, Shihua Luo, Jianhua Liu, Lei Zheng
Antibiotic resistance associated with the mcr-1 gene of Gram-negative bacteria, which confers resistance to drugs of last resort and has the potential to spread via plasmids, is one of the most pressing issues facing global health today. Point-of-care testing for the mcr-1 gene is needed to aid in the identification of colistin resistance in the field and to control its horizontal transmission. Here, we report the successful development of an enzyme-free homogenous electrochemical strategy for sensitive detection of the antibiotic resistance gene mcr-1 using the hybridization chain reaction and mcr-1-specific toehold probe. The long double-stranded DNA polymer produced using this strategy could be detected by assessing the diffusion of methylene blue towards the surface of a screen-printed gold electrode. Under optimized conditions, a linear relationship was observed between the variation of peak current and the natural logarithm of the mcr-1 gene concentration in the range of 1 nM to 1 μM with a detection limit of 0.78 nM (S/N = 3). This enzyme-free, isothermal platform is a rapid, portable, disposable, and sensitive method for detection of plasmid-mediated colistin resistance.
Solid-phase extraction of phospholipids using mesoporous silica nanoparticles: application to human milk samples Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-05-11 Héctor Martínez Pérez-Cejuela, Isabel Ten-Doménech, Jamal El Haskouri, Pedro Amorós, Ernesto F. Simó-Alfonso, José Manuel Herrero-Martínez
In this study, mesoporous silica materials (MSMs) with bimodal pore systems (namely, UVM-7), MCM-41 silica, and a commercial silica-based material were evaluated as solid-phase extraction (SPE) sorbents for the isolation of phospholipids (PLs) using phosphatidylcholine as a test compound. Morphological characterization (including TEM, surface, and size pore measurements) of these materials was carried out. The mechanism of interaction of the target analyte with the MSMs was also studied. With regard to the SPE process, several experimental parameters that affect the extraction performance (e.g., loading and elution solvent, breakthrough volume, loading capacity, and reusability) were investigated. The recommended protocol was applied to the extraction of PLs in human milk fat samples. The extracted PLs were then determined by hydrophilic interaction liquid chromatography (HILIC) using evaporative light scattering detection (ELSD). This work reports the first application of silica-based mesoporous materials to preconcentrate PLs in these complex matrices.
Chiral capillary electrophoresis with UV-excited fluorescence detection for the enantioselective analysis of 9-fluorenylmethoxycarbonyl-derivatized amino acids Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-05-29 Amir Prior, Giulia Coliva, Gerhardus J. de Jong, Govert W. Somsen
The potential of capillary electrophoresis (CE) with ultraviolet (UV)-excited fluorescence detection for sensitive chiral analysis of amino acids (AAs) was investigated. dl-AAs were derivatized with 9-fluorenylmethoxycarbonyl chloride (FMOC)-Cl to allow their fluorescence detection and enhance enantioseparation. Fluorescence detection was achieved employing optical fibers, leading UV excitation light (< 300 nm) from a Xe-Hg lamp to the capillary window, and fluorescence emission to a spectrograph equipped with a charge-coupled device (CCD). Signal averaging over time and emission wavelength intervals was carried out to improve the signal-to-noise ratio of the FMOC-AAs. A background electrolyte (BGE) of 40 mM sodium tetraborate (pH 9.5), containing 15% isopropanol (v/v), 30 mM sodium dodecyl sulfate (SDS), and 30 mM β-cyclodextrin (β-CD), was found optimal for AA chemo- and enantioseparation. Enantioresolutions of 1.0 or higher were achieved for 16 proteinogenic dl-AAs. Limits of detection (LODs) were in the 10–100-nM range (injected concentration) for the d-AA enantiomers, except for FMOC-d-tryptophan (536 nM) which showed intramolecular fluorescence quenching. Linearity (R2 > 0.997) and repeatability for peak height (relative standard deviations (RSDs) < 7.0%; n = 5) and electrophoretic mobility (RSDs < 0.6%; n = 5) of individual AA enantiomers were established for chiral analysis of dl-AA mixtures. The applicability of the method was investigated by the analysis of cerebrospinal fluid (CSF). Next to l-AAs, endogenous levels of d-glutamine and d-aspartic acid could be measured in CSF revealing enantiomeric ratios of 0.35 and 19.6%, respectively. This indicates the method’s potential for the analysis of low concentrations of d-AAs in presence of abundant l-AAs.
Systematic investigations of endogenous cortisol and cortisone in nails by LC-MS/MS and correlation to hair Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-05-17 Tina M. Binz, Franziska Gaehler, Clarissa D. Voegel, Mathias Hofmann, Markus R. Baumgartner, Thomas Kraemer
Hair samples are increasingly used for measuring the long-term stress mediator cortisol. However, hair is not always available and nails (finger or toe), as a keratinized matrix, may be an alternative to hair. In order to measure cortisol and cortisone in the nail matrix, an LC-MS/MS method has been developed and validated using 13C3-labeled surrogate analytes. Both analytes were measured in ESI negative mode as formic acid adducts. Different sample preparation techniques were assessed, and single-step extraction in methanol was established for determination of cortisone and cortisol in the nail matrix. The method was successfully validated with limits of detection (LOD) and limits of quantification (LOQ) of 0.5 and 1.0 pg/mg for cortisol and cortisone, respectively. The calibration curve was linear up to a concentration of 500 pg/mg. Recovery was good for both analytes and showed values over 50%. Matrix effects with ion suppression occurred for both substances but could be corrected by the use of internal standard. Accuracy and precision were in the accepted range of ± 20% for both substances. The method was successfully applied to determine cortisol and cortisone concentrations in authentic nail samples. Cortisol and cortisone concentrations varied significantly among different fingernails, being highest in the little fingernails and lowest in the thumbnails. It could be shown that even in only 1 mg nail sample cortisol and cortisone can be reliably quantified. No correlation between hair and nail cortisol and cortisone concentrations could be found. Furthermore, cortisol and cortisone concentrations were significantly higher in hair.
Compensation for matrix effects in GC analysis of pesticides by using cucumber extract Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-09 Hyeyoung Kwon, Michelangelo Anastassiades, Daniela Dörk, Su-Myoung Hong, Byeong-Chul Moon
Matrix effects (MEs) can adversely affect quantification in pesticide residue analysis using GC. Analyte protectants (APs) can effectively interact with and mask active sites in the GC system, and are added individually or in combination to sample extracts and calibration solutions to minimize errors related to MEs. Unfortunately, APs cannot sufficiently compensate for MEs in all cases. Plant extracts, containing a broad range of natural compounds with AP properties, can also be used for this purpose. In this study, the applicability of cucumber extract as a natural AP mixture was investigated both alone and in combination with traditional APs. Extracts of two selected difficult matrices (onion and garlic) were prepared according to the citrate-buffered QuEChERS (quick, easy, cheap, effective, rugged, and safe) procedure. ME values of 40 representative GC-amenable pesticides were compared when calibrating against standards in pure solvent and in cucumber extract, with and without the addition of APs. Using a GC system with a contaminated inlet liner, the use of a cucumber-based calibration solution decreased MEs remarkably. The combination of APs with cucumber raw extract further decreased MEs, resulting in more than 85% of the tested pesticides showing ≤ 10% ME in onion and ≤ 20% ME in garlic. These results demonstrate that the preparation of calibration standards based on cucumber extracts (with or without the addition of APs) is a very useful and practical approach to compensate for MEs in pesticide residue analysis using QuEChERS and GC-MS/MS. The use of various internal standards is furthermore critically discussed.
Development of immunosorbents for the analysis of forchlorfenuron in fruit juices by ion mobility spectrometry Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-07 Alejandro Orellana-Silla, Sergio Armenta, Miguel de la Guardia, Josep V. Mercader, Francesc A. Esteve-Turrillas
The advantages of using smart materials as immunosorbents in the analysis of complex matrices by ion mobility spectrometry (IMS) have been highlighted in this study. A novel analytical method has been proposed for the sensitive, selective, and fast determination of residues of the plant growth regulator forchlorfenuron in fruit juices. Three different monoclonal antibodies (s3#22, p2#21, and p6#41) were employed for the production of immunosorbents, based on Sepharose gel beads, which were characterized in terms of loading capacity, solvent resistance, and repeatability for its use in solid-phase extraction (SPE). Immunosorbents that were prepared with antibody p6#44 provided the best performance, with a loading capacity of 0.97 μg, a 10% (v/v) 2-propanol tolerance, and a reusability of at least eight uses. The SPE procedure involved the use of a column with 0.15 g Sepharose beads, containing 0.5 mg antibody, which was loaded to 20 mL of the sample, washed with 2 mL of water plus 2 mL of 10% (v/v) 2-propanol, and eluted with 2 mL of 2-propanol. The cleaned extract was directly analyzed by IMS, giving a limit of detection of 2 μg L−1 with a relative standard deviation of 7.6%. Trueness was assessed by the analysis of blank grape and kiwifruit juice samples spiked with forchlorfenuron concentrations from 10 to 400 μg L−1, with recoveries from 80 to 115%. The analytical performance of the proposed immunosorbent was compared with conventional extraction and cleanup methods, such as QuEChERS and C18-based SPE, giving the cleanest extracts for accurate determinations of forchlorfenuron by IMS.
Isolation of transferrin by imprinted nanoparticles with magnetic deep eutectic solvents as monomer Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-07 Yida Zhang, Huawei Cao, Qiangwei Huang, Xiaoyan Liu, Haixia Zhang
Transferrin (TrF) is a very important human body glycoprotein and a clinical biomarker which controls the body’s iron ion channels and iron ion balance. Any change in TrF concentration and isoform also reflects the emergence of some diseases. In this work, we prepared magnetic molecularly imprinted nanoparticles (deep eutectic solvent-molecular imprinting polymers [DES-MIPs]) with a deep eutectic solvent (DES) as a functional monomer to separate TrF in human serum. The DES dosage for MIP, pH value, and time for adsorption have been optimized, and these materials show special adsorption properties for TrF. The maximum adsorption capacity (Qmax) and dissociation constant KL of the MIP by the Langmuir adsorption curve (R2 = 0.9949) were 37.5 mg/g and 0.015 g/L, respectively. The imprinting factor of the MIP is 3.50 with relative standard deviation (5.63%). In summary, the use of DES as a functional monomer in molecular imprinting technology provides a novel, efficient, and biocompatible method for the isolation and purification of proteins.
Chiral and molecular recognition of monosaccharides by photoexcited tryptophan in cold gas-phase noncovalent complexes as a model for chemical evolution in interstellar molecular clouds Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-07 Akimasa Fujihara, Yusuke Okawa
Chiral and molecular recognition between amino acid and sugar molecules and their implications for chemical evolution were investigated using a tandem mass spectrometer equipped with an electrospray ionization source and a cold ion trap. Ultraviolet photodissociation of mass-selected and temperature-controlled gas-phase noncovalent complexes of protonated tryptophan (Trp) and monosaccharide enantiomers, such as aldohexose, aldopentose, and deoxyhexose, was examined as a model for chemical evolution in interstellar molecular clouds. Upon photoexcitation of noncovalent heterochiral H+(l-Trp)(d-aldohexose) complexes, NH2CHCOOH loss from protonated Trp via Cα–Cβ bond cleavage occurred. Conversely, in homochiral H+(l-Trp)(l-aldohexose), the energy absorbed by Trp was released through the detachment of aldohexose, and dissociation of the amino acid was suppressed. In the photodissociation mass spectra of protonated Trp with aldopentose and deoxyhexose, which lacks the OH group of aldohexose, no dissociation of the molecules in the complexes or differences between enantiomers were observed. These results indicate that the OH groups in monosaccharides contribute to enantiomer-selective photodissociation in molecular clouds. The differences observed between enantiomers in the photodissociation mass spectra were applied to distinguishing and quantifying aldohexose enantiomers in solution using l-Trp as a chiral probe. The enantiomeric excesses of aldohexoses in solution could be determined from a single photodissociation mass spectrum by reference to the relative ion intensities for the NH2CHCOOH-elimination product and H+(l-Trp) formed via detachment of aldohexose. This analysis method could also distinguish and quantify two d-aldohexose mixtures, where l-Trp was employed as an isomer probe.
Immunoassay and amperometric biosensor approaches for the detection of deltamethrin in seawater Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-07 Philipp Fruhmann, Ana Sanchis, Lisa Mayerhuber, Tünde Vanka, Christoph Kleber, J.-Pablo Salvador, M.-Pilar Marco
The study of an enzyme-linked immunosorbent assay (ELISA) and an amperometric biosensor for the detection of the pyrethroid deltamethrin in seawater is reported. The preparation of specific polyclonal antibodies is addressed using two immunizing haptens based on deltamethrin and cypermethrin compounds, with a spacer arm placed at the cyano residue in the pyrethroid structure. Different conjugates based on bovine serum albumin and aminodextran are prepared depending on the lipophilic profile of the competitor haptens studied. A reproducible and sensitive indirect competitive ELISA is developed, reaching a limit of detection of 1.2 ± 0.04 μg L−1 and an IC50 value of 21.4 ± 0.3 μg L−1 (both n = 3). For validation of the assays described, artificial seawater samples fortified with deltamethrin are analyzed. For the ELISA assay, these accuracy studies reported a slope of 0.904. An amperometric immunosensor is developed using the same immunoreagents and achieving a comparable detectability in terms of LOD of 4.7 μg L−1, measuring seawater without any pretreatment. These results suggest that both techniques can be used as rapid and simple analytical methods for deltamethrin quantification in seawater samples, which are great candidates for initial environmental screening programs.
Issues with analyzing noble gases using gas chromatography with thermal conductivity detection Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-06 George C. Rhoderick, Michael E. Kelley, Lyn Gameson, Kimberly J. Harris, Joseph T. Hodges
The noble gases, namely neon, argon, krypton and xenon, have many uses including in incandescent and gas discharge lighting, in plasma televisions, shielding gas in welding, in lasers for surgery and semiconductors, and in magnetic resonance imaging (MRI) of the lungs. When incorporating these noble gases in industries, especially the medical field, it is important to know accurately the composition of the noble gas mixture. Therefore, there is a need for accurate gas standards that can be used to determine the noble gas amount-of-substance fraction in the appropriate mixture application. A recent comparison of mixtures containing four noble gases in a helium balance showed mixed results among National Metrology Institutes. Significant differences, 0.7 to 3.8% relative, were seen in the analytical amount-of-substance assignments versus the gravimetric value of the noble gases in the comparison mixture when using “binary standards”, i.e. neon in helium, argon in helium and krypton in helium, as applied by the National Institute of Standards and Technology. Post-comparison studies showed that when all four noble gases were included in the standards, the agreement between analytical and gravimetric values was within 0.05% relative. Further research revealed that different carrier gases (hydrogen, helium and nitrogen) resulted in varying differences between the analytical and gravimetric values assignments. This paper will discuss the findings of these analytical comparisons.
Reference database design for the automated analysis of microplastic samples based on Fourier transform infrared (FTIR) spectroscopy Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-06 Sebastian Primpke, Marisa Wirth, Claudia Lorenz, Gunnar Gerdts
The identification of microplastics becomes increasingly challenging with decreasing particle size and increasing sample heterogeneity. The analysis of microplastic samples by Fourier transform infrared (FTIR) spectroscopy is a versatile, bias-free tool to succeed at this task. In this study, we provide an adaptable reference database, which can be applied to single-particle identification as well as methods like chemical imaging based on FTIR microscopy. The large datasets generated by chemical imaging can be further investigated by automated analysis, which does, however, require a carefully designed database. The novel database design is based on the hierarchical cluster analysis of reference spectra in the spectral range from 3600 to 1250 cm−1. The hereby generated database entries were optimized for the automated analysis software with defined reference datasets. The design was further tested for its customizability with additional entries. The final reference database was extensively tested on reference datasets and environmental samples. Data quality by means of correct particle identification and depiction significantly increased compared to that of previous databases, proving the applicability of the concept and highlighting the importance of this work. Our novel database provides a reference point for data comparison with future and previous microplastic studies that are based on different databases.
Interactions between elastin-like peptides and an insulating poly( ortho -aminophenol) membrane investigated by AFM and XPS Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-06 Maria Elvira Carbone, Rosanna Ciriello, Pasquale Moscarelli, Federica Boraldi, Giuliana Bianco, Antonio Guerrieri, Brigida Bochicchio, Antonietta Pepe, Daniela Quaglino, Anna Maria Salvi
This investigation was undertaken to explore the mutual recognition of the pentapeptide (ValGlyGlyValGly)n, a hydrophobic elastin-like peptide (ELP), suspended in deionized water in monomer (n = 1) and trimer (n = 3) forms and the outer surface of a very thin, insulating polymer, poly(ortho-aminophenol) (PoAP), electrochemically grown on a platinum foil by cyclic voltammetry in a neutral medium (phosphate-buffered saline, I = 0.1M) immersed in the suspension. As a prior task, the proved propensity of the ValGlyGlyValGly sequence, at the given minimal length (three or more repeats), to self-assemble into amyloid-like fibrils when solubilized in an aqueous environment was considered within the framework of testing PoAP surfaces for the specific detection of amyloid precursors. From our knowledge of the chemical structure and physical properties of both biomacromolecule families obtained in previous studies, we focused on the efficacy of the binding sites offered to ELP fibrils by PoAP in its as-prepared form or properly modified either by postsynthesis oxidation or by adsorption/entrapping of ELP monomer(s) with or without protecting terminal groups. Consistent with all methods of preparation, the best surfaces, recognizable by the trimer fibrils, are those modified to carry a larger number of carbonyls, particularly by entrapment of ELP monomer(s) during PoAP electrosynthesis using an imprinting-inspired method. The degree of attachment of fibrillar aggregates, detected by atomic force microscopy and X-ray photoelectron spectroscopy, provides unequivocal evidence of the cooperative forces involving PoAP–ELP interactions. The results obtained suggest the prospect of using the proposed Pt/PoAP/ELP systems as biodetectors in Alzheimer disease.
Correction to: Monitoring dynamic release of intracellular hydrogen peroxide through a microelectrode based enzymatic biosensor Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-05 Hang Zhang, Jun Ruan, Weiwei Liu, Xuerui Jiang, Tianyu Du, Hui Jiang, Alberto Pasquarelli, Kay-Eberhard Gottschalk, Xuemei Wang
The authors would like to call the reader’s attention to the fact that unfortunately Alberto Pasquarelli’s and Kay-Eberhard Gottschalk’s affiliations were wrong in the original publication.
Ionic liquids on optical sensors for gaseous carbon dioxide Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-05 M. D. Fernández-Ramos, M. L. Aguayo-López, I. Pérez de Vargas-Sansalvador, L. F. Capitán-Vallvey
This work presents a study on the influence of eight different ionic liquids (ILs) in the composition of dry membranes used for gaseous CO2 optical sensing. The presence of CO2 causes a displacement of a colorimetric pH indicator toward its acid form that increases the emission intensity of the luminophore by an inner filter process. The influence of ILs in the membrane on the stability and dynamic behavior—usually the main drawbacks of these sensors—of the membranes is studied. The characterization of the different membranes prepared was carried out and the discussion of the results is presented. In all cases, the response and recovery times improved considerably, with the best case being response times of only 10 s and recovery times of 48 s, compared to response and recovery times of 41 and 100 s, respectively, for membranes without IL. The useful life of the detection membranes is also considerably longer than that of membranes that do not include IL, at least 292 days in the best case. The sensing membrane without luminophore and only containing the pH indicator is proposed for the color-based measurement of CO2 using a digital camera for possible use in food-packaging technology.
Feasibility study of a candidate reference material for ions in PM 2.5 : does commutability matter also for inorganic matrices? Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-04 G. Emma, J. Snell, J. Charoud-Got, A. Held, H. Emons
The existing Air Quality Directive 2008/50/EC establishes within the European Union (EU) member states limit values for fine air particulate matter (PM2.5) including the possibility to discount natural sources of pollution when assessing compliance with the legislation. In proving this, EU member states shall determine, amongst others, the rural background concentration of some anions (Cl−, NO3− and SO42−) and cations (Na+, NH4+, K+, Ca2+ and Mg2+). To deliver reliable data and to comply with the data quality objectives of the legislation, environmental control laboratories should use certified reference materials (CRMs) to validate or verify the performance of their analytical methods. Since no CRMs for anions and cations in PM2.5 are presently available, we present the commutability issues encountered during the first attempt to develop such a material. We demonstrate that a dust, collected in a road tunnel and previously used for the production of two CRMs of a PM10-like material, does not behave as an authentic fine particulate matter collected according to EN12341:2014 when measured by an established method proposed by the European Committee for Standardization (CEN/TR 16269:2011). The water-soluble fractions of SO42−, NH4+, K+, Ca2+ and Mg2+ in a PM2.5-like candidate CRM produced from that road tunnel dust are only fully extracted after 3 h of sonication and not after 30 min, as stated in the method. Moreover, we found that the particle size of the test material influenced the extraction yield of K+, Ca2+ and Mg2+, suggesting that these ionic species were incorporated in the core of the particles and inaccessible to the extraction procedure. These particular features make the material unsuitable for the measurements of ions with the CEN method. The difference in the extraction time can be seen as a commutability issue and the candidate CRM should be considered as not commutable with routine samples. This demonstrates that commutability studies should not only be considered for clinical CRMs, but also for inorganic CRMs when they are intended to be used to quantify operationally defined analytes.
Determination of the β-glycosylate fraction of contaminants of emerging concern in lettuce ( Lactuca sativa L.) grown under controlled conditions Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-04 Carlos Hurtado, Carmen Domínguez, Pere Clapés, Josep M. Bayona
The uptake of a large variety of contaminants of emerging concern (CECs) by crops has already been reported, and the occurrence of phase II metabolites or conjugates has only been detected in plant cell cultures. However, the extent of their formation under cropping conditions is largely unknown. In this study, an analytical strategy to assess the conjugation of 11 CECs in lettuce (Lactuca sativa L.) irrigated with different concentrations (0, 0.05, 0.5, 5, and 50 μg L−1) of CECs was developed. The methodology involved enzymatic digestion with β-glucosidase to obtain the total fraction (free form + conjugates) of CECs. The conjugation fraction was then obtained based on the difference. The highest extent of conjugation (i.e., 27 to 83%) was found with the most hydrophobic compounds, such as bisphenol A, carbamazepine, methyl paraben, and triclosan. So, the CEC conjugate fraction cannot be neglected in the estimate of human daily intake.
Sheathless coupling of microchip electrophoresis to ESI-MS utilising an integrated photo polymerised membrane for electric contacting Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-04 T. Scholl, C. Dietze, M. Schmidt, S. Ohla, D. Belder
In this article, we present a novel approach for the sheathless coupling of microchip electrophoresis (MCE) with electrospray mass spectrometry (ESI-MS). The key element is an ion-conductive hydrogel membrane, placed between the separation channel and an adjacent microfluidic supporting channel, contacted via platinum electrodes. This solves the persistent challenge in hyphenation of mass spectrometry to chip electrophoresis, to ensure a reliable electrical connection at the end of the electrophoresis channel without sacrificing separation performance and sensitivity. Stable electric contacting is achieved via a Y-shaped supporting channel structure, separated from the main channel by a photo polymerised, ion permeable hydrogel membrane. Thus, the potential gradient required for performing electrophoretic separations can be generated while simultaneously preventing gas formation due to electrolysis. In contrast to conventional make-up or sheathflow approaches, sample dilution is also avoided. Rapid prototyping allowed the study of different chip-based approaches, i.e. sheathless, open sheathflow and electrode support channel designs, for coupling MCE to ESI-MS. The performance was evaluated with fluorescence microscopy and mass spectrometric detection. The obtained results revealed that the detection sensitivity obtained in such Y-channel chips with integrated hydrogel membranes was superior because sample dilution or loss was prevented. Furthermore, band broadening is reduced compared to similar open structures without a membrane.
Employing proteomics to understand the effects of nutritional intervention in cancer treatment Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-04 Monica M. Schroll, Amanda B. Hummon
Lifestyle optimizations are implementable changes that can have an impact on health and disease. Nutrition is a lifestyle optimization that has been shown to be of great importance in cancer initiation, progression, and metastasis. Dozens of clinical trials are currently in progress that focus on the nutritional modifications that cancer patients can make prior to and during medical care that increase the efficacy of treatment. In this review, we discuss various nutritional inventions for cancer patients and the analytical approaches to characterize the downstream molecular effects. We first begin by briefly explaining the many different forms of nutritional intervention currently being used in cancer treatment as well as their motivating biology. The forms of nutrient modulation described in this review include calorie restriction, the different practices of fasting, and carbohydrate restriction. The review then shifts to explain how proteomics is used to determine biomarkers of cancer and how it can be utilized in the future to determine the metabolic phenotype of a tumor, and inform physicians if nutritional intervention should be recommended for a cancer patient. Nutrigenomics aims to understand the relationship of nutrients and gene expression and can be used to understand the downstream molecular effects of nutrition restriction, partially through proteomic analysis. Proteomics is just beginning to be used as cancer diagnostic and predictive tools. However, these approaches have not been used to their full potential to understand nutritional intervention in cancer.
Headspace analysis for screening of volatile organic compound profiles of electronic juice bulk material Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-04 Ryan F. LeBouf, Dru A. Burns, Anand Ranpara, Kathleen Attfield, Leonard Zwack, Aleksandr B. Stefaniak
The use of electronic nicotine delivery systems continues to gain popularity, and there is concern for potential health risks from inhalation of aerosol and vapor produced by these devices. An analytical method was developed that provided quantitative and qualitative chemical information for characterizing the volatile constituents of bulk electronic cigarette liquids (e-liquids) using a static headspace technique. Volatile organic compounds (VOCs) were screened from a convenience sample of 146 e-liquids by equilibrating 1 g of each e-liquid in amber vials for 24 h at room temperature. Headspace was transferred to an evacuated canister and quantitatively analyzed for 20 VOCs as well as tentatively identified compounds using a preconcentrator/gas chromatography/mass spectrometer system. The e-liquids were classified into flavor categories including brown, fruit, hybrid dairy, menthol, mint, none, tobacco, and other. 2,3-Butanedione was found at the highest concentration in brown flavor types, but was also found in fruit, hybrid dairy, and menthol flavor types. Benzene was observed at concentrations that are concerning given the carcinogenicity of this compound (max 1.6 ppm in a fruit flavor type). The proposed headspace analysis technique coupled with partition coefficients allows for a rapid and sensitive prediction of the volatile content in the liquid. The technique does not require onerous sample preparation, dilution with organic solvents, or sampling at elevated temperatures. Static headspace screening of e-liquids allows for the identification of volatile chemical constituents which is critical for identifying and controlling emission of potentially hazardous constituents in the workplace.
Preparation and evaluation of surface-bonded phenylglycine zwitterionic stationary phase Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-03 Huanjun Peng, Xiang Wang, Jingdong Peng, Yan He, Yu Chen, Fang Chen, Shiyu Li
4-Hydroxy-d-phenylglycine was modified with methacrylic anhydride and then immobilized on silica through thiol-initiated surface polymerization; the prepared material was applied as stationary phase for HPLC. The obtained stationary phase was characterized by elemental analysis, infrared spectroscopy, and thermogravimetric analysis. The chromatographic performance of the packed column was evaluated in reversed-phase liquid chromatograph (RPLC) and hydrophilic interaction liquid chromatograph (HILIC) mode; this column has shown excellent selectivity to both the hydrophobic and hydrophilic solutes. The selectivity towards polycyclic aromatic hydrocarbons relative to that towards alkylbenzenes exhibited by the prepared column was higher than the corresponding selectivity exhibited by commercial C18 column, which could be explained by electronic π-π interaction between phenylglycine and electron-rich aromatic rings. On the other hand, the prepared column has also shown better selectivity for polar compounds, which was based on the multiple interaction and retention mechanisms. It was also used to separate sulfonamides and organic acid compared with a commercial C18 and HILIC column; the results show its great chromatographic performance with distinctive selectivity. All the results indicated the prepared column had potential application in a wide range.
Round robin study of formalin-fixed paraffin-embedded tissues in mass spectrometry imaging Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-03 Achim Buck, Bram Heijs, Birte Beine, Jan Schepers, Alberto Cassese, Ron M. A. Heeren, Liam A. McDonnell, Corinna Henkel, Axel Walch, Benjamin Balluff
Mass spectrometry imaging (MSI) has provided many results with translational character, which still have to be proven robust in large patient cohorts and across different centers. Although formalin-fixed paraffin-embedded (FFPE) specimens are most common in clinical practice, no MSI multicenter study has been reported for FFPE samples. Here, we report the results of the first round robin MSI study on FFPE tissues with the goal to investigate the consequences of inter- and intracenter technical variation on masking biological effects. A total of four centers were involved with similar MSI instrumentation and sample preparation equipment. A FFPE multi-organ tissue microarray containing eight different types of tissue was analyzed on a peptide and metabolite level, which enabled investigating different molecular and biological differences. Statistical analyses revealed that peptide intercenter variation was significantly lower and metabolite intercenter variation was significantly higher than the respective intracenter variations. When looking at relative univariate effects of mass signals with statistical discriminatory power, the metabolite data was more reproducible across centers compared to the peptide data. With respect to absolute effects (cross-center common intensity scale), multivariate classifiers were able to reach on average > 90% accuracy for peptides and > 80% for metabolites if trained with sufficient amount of cross-center data. Overall, our study showed that MSI data from FFPE samples could be reproduced to a high degree across centers. While metabolite data exhibited more reproducibility with respect to relative effects, peptide data-based classifiers were more directly transferable between centers and therefore more robust than expected.
Stepwise frontal affinity chromatography model for drug and protein interaction Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-02 Xiaoshuang He, Yue Sui, Sicen Wang
Frontal affinity chromatography is an efficient technique that combines affinity interaction and high-performance liquid chromatography, and frontal analysis has been used in studying the interaction between drugs and proteins. Based on frontal analysis, stepwise frontal analysis has been established. The present study aimed to use the Lineweaver–Burk plot in stepwise frontal analysis by taking the weighted average of time data. Commercial human serum albumin (HSA) and alpha-1-acid glycoprotein (AGP) columns were used as an affinity column. Warfarin and digitoxin were chosen as model drugs for the HSA column, whereas verapamil and tamsulosin were selected as model drugs for the AGP column. The time data obtained by frontal analysis and stepwise frontal analysis were compared, and the results revealed good correlation (r2 = 0.9946–0.9998). Frontal analysis and stepwise frontal analysis were also used to analyze the equilibrium dissociation constants (Kd) of model drugs on the HSA and AGP columns. The Kd values were compared with literature values, which revealed the same order of magnitude. These results illustrate that conversion of the time data is reasonable and feasible. The Lineweaver–Burk plot can be used in the stepwise frontal analysis model to study the characteristics of the interaction between drugs and proteins.
Graphene oxide-based biosensing platform for rapid and sensitive detection of HIV-1 protease Anal. Bioanal. Chem. (IF 3.307) Pub Date : 2018-07-02 Youwen Zhang, Xiaohan Chen, Golbarg M. Roozbahani, Xiyun Guan
HIV-1 protease is essential for the life cycle of the human immunodeficiency virus (HIV), and is one of the most important clinical targets for antiretroviral therapies. In this work, we developed a graphene oxide (GO)-based fluorescence biosensing platform for the rapid, sensitive, and accurate detection of HIV-1 protease, in which fluorescent-labeled HIV-1 protease substrate peptide molecules were covalently linked to GO. In the absence of HIV-1 protease, fluorescein was effectively quenched by GO. In contrast, in the presence of HIV-1 protease, it would cleave the substrate peptide into short fragments, thus producing fluorescence. Based on this sensing strategy, HIV-1 protease could be detected at as low as 1.18 ng/mL. More importantly, the sensor could successfully detect HIV-1 protease in human serum. Such GO-based fluorescent sensors may find useful applications in many fields, including diagnosis of protease-related diseases, as well as sensitive and high-throughput screening of drug candidates.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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