Dispersive liquid-liquid microextraction coupled with derivatization: a review of different modes, applications, and green aspects Trends Anal. Chem. (IF 7.034) Pub Date : 2018-07-17 Muhammad Sajid
DLLME is widely used as a sample preparation technique due to its unique advantages of fast extraction, low solvent consumption, high enrichment factors, and low cost. DLLME extracts are generally analyzed by gas or liquid chromatography coupled with different detection systems. However, GC or LC cannot analyze/separate many analytes due to their structural properties. Similarly, some of the analytes are not sensitive to commonly used detectors. In such cases, a derivatization process (chemical conversion) is often applied to improve the structural features of the analytes to make them compatible with separation and detection system. The coupling of derivatization with DLLME is a simple way to accomplish the job using minimum volumes of the derivatizing reagents and reducing their impact on workers and the environment. This review explains the different modes of DLLME coupled derivatizations, their applications, and green aspects in a systematic way.
Instantaneous identification of hazardous explosive-related materials using laser induced photoacoustic spectroscopy Trends Anal. Chem. (IF 7.034) Pub Date : 2018-07-17 Yasser H. El-Sharkawy, Sherif Elbasuney, Ashraf El-sherif, Mohamed Eltahlawy, H.S. Ayoub
Common fertilizers have the oxidizing and the reducing elements on the same molecule; therefore they have an explosiveness nature. Reliable approach for fast recognition of such compounds is an urgent need. Laser induced photoacoustic spectroscopy is an interesting technology as it can offer characteristic thermal, acoustical, and light absorption coefficient. The paper deals with a photoacoustic spectroscopy technique to record the characteristic photoacoustic frequency-response of common explosive-related materials. The proper stimulating light was generated using pulsed Q-switched Nd:YAG laser at 1064 nm. Photoacoustic signature for each investigated material was recorded using high response piezoelectric transducer. The captured signal was processed using novel digital algorithm designed for time and frequency domain analysis to achieve good discrimination between different explosive-related materials. Each investigated material demonstrated a characteristic absorption coefficient as well as frequency response with maximum amplitude at 47.9, 49, and 46 MHz for urea nitrate, ammonium nitrate, and ammonium perchlorate respectively.
Synthesis, structure, and DNA binding/cleavage of two novel binuclear Co(II) complexes Spectrochim. Acta. A Mol. Biomol. Spectrosc. (IF 2.88) Pub Date : 2018-07-18 Ying-Ying Kou, Mei-Ling Li, Xiang-Hao Ren
In this study, two novel binuclear Co(II) complexes, [Co4(L1)2(CH3CH2O)4·5.5H2O (1) and [Co2(L2)2(CH3COO)(H2O)]·2CH3OH·3H2O (2)], with the ligands H3L1 and H2L2 were synthesized and structurally characterized using single crystal X-ray diffraction. The crystal structures of complex 1 and 2 belong to a monoclinic system with space group of P2(1)/n and triclinic system with space group of P-1, respectively. Their interaction with CT-DNA was investigated using electron absorption and fluorescent spectroscopy. The apparent binding constants (Kapp) of two complexes (1 and 2) were determined to be 5.34 × 105 and 5.82 × 105, respectively, and both exhibited a moderate intensity of insertion with 2 > 1. Fluorescence quenching studies indicated that the fluorescence quenching mechanism of complex 1 is dynamic quenching and that of complex 2 is a static quenching mechanism. The chemical nuclease activity of the complexes was studied using agarose gel electrophoresis. The results suggest that when H2O2 is added, complexes 1 and 2 exhibit chemical nuclease activity. The cleavage mechanisms between the complexes and plasmid DNA are the likely oxidative cleavage process of hydroxyl radical (OH) and singlet oxygen (1O2) as active species.
Comparison of several third-order correction algorithms applied to fluorescence excitation–emission-sample data array: Interference-free determination of polycyclic aromatic hydrocarbons in water pollution Spectrochim. Acta. A Mol. Biomol. Spectrosc. (IF 2.88) Pub Date : 2018-07-18 Zhe Yang, Tingting Liu, Yutian Wang, Yuanyuan Yuan, Fengkai Shang
Interference-free determination of polycyclic aromatic hydrocarbons (PAHs) in water pollution is proposed based on third-order correction algorithms with quadrilinear component modeling applied to the constructed four way fluorescence excitation–emission-sample data array with higher accuracy and better predictive ability than second-order (three-dimension) correction. Alternating weighted residue constraint quadrilinear decomposition (AWRCQLD), quadrilinear parallel factor analysis (4-PARAFAC), alternate penalty quadrilinear decomposition (APQLD) and alternate penalty trilinear decomposition (APTLD) are applied to acenaphthene (ANA), naphthalene (NAP) and fluorene (FLU) respectively. Fulvic acid affects PAHs determination seriously in real-world situation, so it is simulated as an interfering agent. Excitation-emission fluorescence matrixes (EEMs) of PAHs are measured at different volumes of fulvic acid simulated different interference conditions, to construct a four-way data array. After the four-way spectra data is analyzed by AWRCQLD, 4-PARAFAC, and APQLD, three-way EEMs analyzed by APTLD, results show that, on the one hand, PAHs can be measured more accurately with four-way data combined with third-order calibration than lower-order. On the other hand, AWRCQLD algorithm can reflect the superiority of third-order advantage better with higher recovery rate and smaller root mean square error, than other third-order or second-order correction algorithms.
Temporal changes in field calibration relationships for Aeroqual S500 O3 and NO2 sensor-based monitors Sens Actuators B Chem. (IF 5.667) Pub Date : 2018-07-18 Nicola Masey, Jonathan Gillespie, Eliani Ezani, Chun Lin, Hao Wu, Neil S. Ferguson, Scott Hamilton, Mathew R. Heal, Iain J. Beverland
Sensor-based monitors are increasingly used to measure air pollutant concentrations, but require calibration under field conditions. We made intermittent comparisons (6 times over 6-month period) between ozone and nitrogen dioxide concentrations measured by Aeroqual gas-sensitive semiconductor (O3) and electrochemical (NO2) sensors (two of each) and reference analysers in the UK Automatic Urban and Rural Network. Each deployment period was split into equal (n = 48 h) training and test datasets, to derive and test calibration equations respectively. We observed significant bivariate linear relationships between Aeroqual O3 and Reference O3 concentrations, and significant multiple linear relationships between Aeroqual NO2 and both Reference NO2 and Aeroqual O3 concentrations. Changes in monitor responses over time (including apparent baseline drift in O3 sensor output, and discrepancies between the 2 Aeroqual NO2 sensors) resulted in relatively inaccurate concentrations estimates (cf. reference concentrations) from calibration equations derived in the first training period and applied to subsequent test deployments (e.g. NO2 RMSE = 47.2 μg m-3 (n = 286) for a dataset of all test periods combined, for one of the two monitor pairs). Substantial improvements in accuracy of estimated concentrations were achieved by combination of repeated intermittent training data into a single calibration dataset (NO2 RMSE = 8.5 μg m-3 for same test dataset described above). This latter approach to field calibration is recommended.
Label-Free Distinction between p53+/+ and p53 -/- Colon Cancer Cells Using a Graphene Based SERS Platform Biosens. Bioelectron. (IF 8.173) Pub Date : 2018-07-18 Owen Liang, Pu Wang, Ming Xia, Catherine Augello, Fan Yang, Gang Niu, Huinan Liu, Ya-Hong Xie
Surface-Enhanced Raman Scattering (SERS) is used to differentiate two colon cancer cell line HCT 116, that is, to distinguish a TP53 gene knockout cell line (p53 -/-) from a wild type (p53 +/+). A label-free graphene/gold nanopyramid based SERS platform, combined with the multivariate analysis: principal component analysis, is used to profile live, dead, and burst colon cancer cells suspended in simulated body fluid (SBF). The graphene sheet permits SERS hotspot identification and provides a chemical enhancement for the biological constituents. This study found that a unique fingerprint exists for three different states of the cell, burst, live, and dead, which were used to differentiate the p53 +/+ and p53 -/- cell lines. Perceptron with Pocket Algorithm was also coupled with PCA to demonstrate an average of 81% sensitivity and 97% specificity in separating the two cell lines. The demonstration of single gene differentiation shows the great applicable potential of this SERS graphene hybrid platform for cancer diagnosis.
Label-free fluorescent and electrochemical biosensors based on defective G-quadruplexes Biosens. Bioelectron. (IF 8.173) Pub Date : 2018-07-18 Jing Zhang, Liang-Liang Wang, Mei-Feng Hou, Li-Pei Luo, Yi-Juan Liao, Yao-Kun Xia, An Yan, Yun-Ping Weng, Lu-Peng Zeng, Jing-Hua Chen
Abnormal levels of guanine closely associated with plenty of diseases are usually used as a biomarker for clinical diagnosis. In order to detect guanine and its derivatives accurately, in this paper, a defective G-quadruplex (DGQ) containing a G-vacancy at one of its G-quartet layers, and two kinds of G-quadruplex specific indicators including thioflavine T (ThT) and hemin were used for constructing a fluorescent and an electrochemical biosensor, respectively. In brief, a G-rich DNA probe is designed to form either hairpin or DGQ structure. In the absence of guanine, G-rich probes prefer to maintain hairpin structure and nearly have no interaction with ThT or hemin, leading to almost negligible signals. Upon addition of guanine, the G-rich probe fold into DGQ structure and then the G-vacancy in it is filled up immediately by guanine via Hoogsteen hydrogen bonds, resulting canonical G-quadruplex formation. Accordingly, ThT or hemin can selectively combine with G-quadruplex, giving rise to distinct fluorescent or current signal changes for label-free detection of guanine. Benefiting from the perfect discriminative ability of guanine towards DGQ and ThT/hemin against standard G-quadruplex, the fluorescent and electrochemical biosensors present better sensitivity and selectivity for guanine detection with the limit of detection (LOD) as low as 18.26 and 0.36 nM, respectively. Successful attempts were also made in applying the proposed electrochemical biosensor to detect guanine in drugs and urine, obtaining satisfactory recovery rates of 99%~104% and 96% ~106%, respectively.
A single run UPLC-MS/MS method for detection of all EU-Regulated marine toxins Talanta (IF 4.244) Pub Date : 2018-07-18 Inés Rodríguez, Amparo Alfonso, Jesús M. González-Jartín, Mercedes R. Vieytes, Luis M. Botana
A UPLC-MS/MS method has been developed for identification and quantification of hydrophilic and lipophilic marine toxins. The method included the determination of 14 toxins of STX group, 15 lipophilic toxins, 15 toxins of the TTX group and DA. LODs and LOQs for STX group were significantly improved in comparison to the official validated methods and at the same level than other UPLC-MS/MS published methods. The same for lipophilic toxins, with better LODs and LOQs than the EU official method. LOD and LOQ for DA were higher than those obtained with the EU official method. While for TTXs LOD and LOQ were comparable to other validated methods. Validation studies demonstrated acceptable method performance characteristics for linearity, and repeatability between-batch and within-batch. The study demonstrated that the UPLC-MS/MS method provides an excellent tool to determinate hydrophilic and lipophilic toxins and therefore it could be appropriate for routine testing and interlaboratory validation.
Metabolomics data fusion between near infrared spectroscopy and high-resolution mass spectrometry: A synergetic approach to boost performance or induce confusion Talanta (IF 4.244) Pub Date : 2018-07-18 Shengyun Dai, Zhaozhou Lin, Bing Xu, Yuqi Wang, Xinyuan Shi, Yanjiang Qiao, Jiayu Zhang
In general, data fusion can improve the classification performance of the model, but little attention is paid to the influence of the data fusion on the spatial distribution of the modeling samples. In this paper, the effect of data fusion on sample spatial distribution was studied through integrating NIR data and UHPLC-HRMS data for sulfur-fumigated Chinses herb medicine. Twelve samples collected from four different geographical origins were sulfur fumigated in the lab, and then metabolomics analysis was conducted using NIR and UHPLC-LTQ-Orbitrap mass spectrometer. First of all, the discriminating power of each technique was respectively examined based on PCA analysis. Secondly, combining NIR and UHPLC-HRMS data sets together with or without variable selection was parallelly compared. The results demonstrated that the discriminable ability was remarkably improved after data fusion, indicating data fusion could visualize variable selection and enhance group separation. Samples in the margin between two classes of samples may increase the experience error but has positive effect on the separation direction. Besides, an interesting feature extraction could obtain better discriminable effect than common data fusion. This study firstly provided a new path to employ a comprehensive analytical approach for discriminating SF Chinese herb medicines to simultaneously benefit from the advantages of several technologies.
Characterization of Human Serum Albumin isoforms by ion exchange chromatography coupled on-line to native mass spectrometry J. Chromatogr. B (IF 2.441) Pub Date : 2018-07-18 Y. Leblanc, N. Bihoreau, G. Chevreux
Human Serum Albumin is the most abundant protein of the plasma and displays a wide range of non-oncotic properties such as antioxidant activity, distribution in tissues and organs of binding molecules and clearance of toxic compounds. Albumin is susceptible to numerous post-translational modifications and particularly related to its free thiol group at Cys34 which is the main circulating scavenger of reactive oxygen species. The characterization of these modifications is of high interest for the diagnosis and treatment of patients with liver diseases and for the structural integrity assessment of albumin as a therapeutic protein.In this study, an ion exchange chromatographic method coupled on-line to native mass spectrometry was developed in order to bridge an effective charge variants separation method with a powerful identification technique for a detailed characterization of albumin isoforms. The chromatographic performance of the method allows the separation of 9 different isoforms that were on-line characterized by MS as oxidized, glycated, deamidated and N/C-terminal truncated forms. The method is also able to detect Cu(II) ions binding to the N-terminal site of the protein which is an important antioxidant feature of albumin. Finally, the method showed preliminary good performance parameters in term of linearity, precision and sensitivity for characterization of purified albumin as well as albumin from raw plasma for clinical and pharmaceutical purposes.
Xanthohumol C, a minor bioactive hop compound: Production, purification strategies and antimicrobial test J. Chromatogr. B (IF 2.441) Pub Date : 2018-07-18 Simon Roehrer, Juergen Behr, Verena Stork, Mara Ramires, Guillaume Médard, Oliver Frank, Karin Kleigrewe, Thomas Hofmann, Mirjana Minceva
Hop has been attracting scientific attention due to its favorable bioactivity properties. It is thus desirable to relate these properties to the specific hop compounds and extract these compounds in highly purified form in order to enhance the effect. The aim of the present study is the isolation of a sufficient amount of the highly purified prenylated minor hop compound xanthohumol C (XNC) for characterizing its bioactivity. Two strategies for the production of XNC were evaluated. The first strategy involved a capture of natural XNC from a xanthohumol (XN)-enriched hop extract (XF) by countercurrent chromatography. In the second approach, a one-step semi-synthesis of XNC was performed starting from XN, which had previously been separated from a natural XN-enriched hop extract. Both methods delivered XNC in sufficient amount and purity (>95%, HPLC), whereas the second strategy was preferable in terms of purity (>99%, HPLC) as well as productivity and solvent consumption. The methods were validated by identifying and quantifying XNC using LC-MS, LC-MS/MS and 1H NMR analysis. The XNC obtained in this way was supplied to several bacterial, yeast and fungal cultures in order to evaluate its antimicrobial effects. For comparison, microorganisms were also treated with the natural XN-enriched hop extract, as well as the prenylated hop compound XN. While still reducing cell proliferation, XNC was found to be less effective than both XF and XN for all studied bacteria and yeasts. Furthermore, for Bacillus subtilis, a strongly pH-dependent minimal inhibition concentration was observed for all three bioactive compounds, lowest at a pH of 5 and highest at a pH of 7.
Quality by design compliant strategy for the development of a liquid chromatography–tandem mass spectrometry method for the determination of selected polyphenols in Diospyros kaki J. Chromatogr. A (IF 3.716) Pub Date : 2018-07-18 C. Ancillotti, S. Orlandini, L. Ciofi, B. Pasquini, C. Caprini, C. Droandi, S. Furlanetto, M. Del Bubba
Diospyros kaki fruits possess great beneficial properties for human health due to their strong antioxidant and antiradical activities related to the high level of bioactive compounds and particularly polyphenols. In this paper a rapid and efficient liquid chromatography–tandem mass spectrometry method for the determination of 38 polyphenolic compounds in Diospyros kaki flesh was developed. The optimization of the chromatographic method was performed applying a Quality by Design approach, which is unexplored in the field of food analysis. The Critical Method Attributes (CMAs) were the critical resolutions of some isobaric compounds and analysis time. The Critical Methods Parameters (CMPs) were related to the characteristics of both the mobile phase and the column: flow rate, temperature, starting organic phase concentration of the mobile phase, formic acid percentage in the eluents, type of organic solvent in the mobile phase and gradient of organic eluents. The effects of the CMPs on the CMAs were evaluated by experimental design, at first carrying out a screening phase by an asymmetric screening matrix and then applying Response Surface Methodology by a Doehlert Design. The quadratic polynomial models postulated to link the CMAs to CMPs were calculated and the Method Operable Design Region was identified with the aid of Monte Carlo simulations as the multidimensional combination of the CMPs that satisfied the requirements for the CMAs with a probability ≥90%. The developed method was applied to real samples obtained by the extraction of Diospyros kaki flesh from two different cultivars (Rojo Brillante and Kaki Tipo), making it possible to obtain extensive information on their polyphenolic profiles.
Use of RhB and BSF as fluorescent tracers for determining pesticide spray distribution Anal. Methods (IF 2.073) Pub Date : 2018-07-18 Wei-cai Qin, Xin-yu Xue, Qing-qing Zhou, Chen Cai, Bao-kun Wang, Yong-kui Jin
Fluorescent tracers are frequently used in spray tests, but their stability under illumination and rate of elution and recovery from the deposition carrier are crucial to the accuracy of the test results. Spectral analysis has shown that the absorbing wavelengths for RhB and BSF are 573.8nm and 494.6nm, respectively, at most under uninterrupted sunlight and their recovery rates are 93.5%~98.2% and 95.5%~99.4%, respectively. In favourable light stability, a great part of both colouring agents can be eluted and recovered from glass slides and mylar card but not so much from filter paper. Because of the tracers being influenced by light, when using a mylar card as a receiver, different coloured plastic boards were used as pads, and it was found that a red pad can increase the recovery of elution by three percent in 2 hours. Our goal was to determine which chemicals would be most suited for use as tracers for the simulation of long-distance transport of pesticides in aerial spraying by evaluating the effects of spraying pattern on spraying deposition and drift potential of pesticide sprays. Tests undertaken on a farm showed that the two colouring agents studied can be effectively used as tracers to investigate droplet deposition of pesticides sprayed by a UAV on paddy rice farms in a low volume. The above test results show that RhB can be feasibly used as a tracer to examine droplet deposition of pesticides aerially sprayed in a low volume.
Graphite nanoparticle as nanoquecher for 17β-estradiol detection using shortening aptamer sequence Analyst (IF 3.864) Pub Date : 2018-07-18 Xiaoli Qi, Hui Hu, Yuesuo Yang, Yunxian Piao
Graphite nanoparticle (GN) with spherical shape and stacked by a few layered graphene sheets is an ideal fluorescent nanoquencher for the fluorophore. We developed a novel aptasensor based on fluorescence resonance energy transfer for sensitive and specific detection of 17β-estradiol (E2) by using the GN as fluorescent nanoquencher and the shorten E2 specific aptamer as sensing probe. The physiological and chemical properties of the aptasensor in responses to the E2 capturing were investigated with atomic force microscopic analysis and E2 detection principle was clarified accordingly. Also it was demonstrated the sensitivity of the aptasensor was affected by the length of aptamers and the particle size of the nanoquenchers, and highest sensitivity for E2 detection was achieved with the shorter aptamer of 35 base sequences and the smaller GN with particle size of around 5 nm. And the detection limit was 1.02 ng/mL. Moreover, it presented no cross reaction with E2 analogs and was successfully utilized for the real environmental water monitoring.
Microstructural characterization of Cu-Sn-Zn electrodeposits produced potentiostatically from acid baths based on trisodium nitrilotriacetic J. Electroanal. Chem. (IF 3.235) Pub Date : 2018-07-17 Marcos F. de Carvalho, Ivani A. Carlos
This study characterizes the Cu-Sn-Zn electrodeposits produced potentiostatically from baths containing different concentrations of Cu2+, Sn2+ and Zn2+ ions and 0.60 M trisodium nitrilotriacetic (NTA) at pH 4.99 (higher stability). Ternary electrodeposits were produced onto AISI 1010 steel substrate at electrodeposition potential of −1.60 V with electrodeposition charge density of 3.0 Ccm−2. Chemical composition of electrodeposits varied significantly, presenting higher Cu content (at.%) than that of other elements. Furthermore, it was verified that the high concentration of Sn2+ ions in the baths hindered the reduction of Zn2+ ions, leading to Zn-poor electrodeposits. Microstructure was generally composed of irregular crystallites and clusters of crystallites or dendrites dispersed on the surface, depending on chemical composition. X-ray diffraction showed formation of the ternary alloy by mixture of the Cu5Zn8, η-Cu6Sn5 and Sn pure phases. In addition, electrodeposits with lower Cu content (at.%) also showed the SnO phase. Surface topography of the electrodeposits presented a rough aspect, with arithmetic roughness varying from 1.83 to 3.90 μm for electrodeposits with lower and higher Sn content (at.%), respectively. Adhesion tests indicated that the highest and lowest adherence percentages to the steel substrate were observed for the electrodeposits with the largest Zn and Sn contents (at.%), respectively.
Preparation of reusable nano N-TiO2/graphene/titanium grid sheet for electrosorption-assisted visible light photoelectrocatalytic degradation of a pesticide: Effect of parameters and neural network modeling J. Electroanal. Chem. (IF 3.235) Pub Date : 2018-07-17 Baharak Ayoubi-Feiz, Mohammad Hossein Mashhadizadeh, Mohsen Sheydaei
Nitrogen doped-TiO2 (N-TiO2) nanoparticles were successfully prepared via manual grinding method. Electrophoretic deposition method has been developed to deposit N-TiO2 nanoparticles and graphene (G) nanoplatelets onto titanium grid sheet. The obtained film (N-TiO2/G) was characterized using FESEM, XRD, BET surface area, XPS, FT-IR, and UV–Vis DRS. In the present work, the removal of diazinon as a common pesticide from aqueous solution was investigated by electrosorption-assisted photoelectrocatalytic process using N-TiO2/G nanocomposite under the visible light irradiation. The removal efficiency of diazinon obtained 80% for the electrosorption-assisted photoelectrocatalytic process; while, it was 28.3% for photocatalytic and 23.7% for electrosorption processes, solely. Moreover, even after five successive cycles, the catalyst exhibited constant activity. An artificial neural network (ANN) model was developed to predict the removal of diazinon solution. The findings indicated that the ANN provided reasonable predictive performance (R2 = 0.9995). The relative importance of each studied variable on the electrosorption-assisted photoelectrocatalytic process was evaluated. Diazinon and electrolyte concentrations were found to be the most significant factors, followed by pH, applied bias potential and contact time. The main intermediates of diazinon degradation were identified using GC-Mass spectrometry.
g-C3N4 nanofibers doped poly(3,4-ethylenedioxythiophene) modified electrode for simultaneous determination of ascorbic acid and acetaminophen J. Electroanal. Chem. (IF 3.235) Pub Date : 2018-07-17 Caiwei Li, Jianhua Xu, Yuting Wu, Yuehua Zhang, Cheng Zhang, Wu Lei, Qingli Hao
A fast and sensitive electrochemical sensor for simultaneous determination of ascorbic acid (AA) and acetaminophen (AP) was proposed based on g-C3N4 nanofibers (h-CN) doped poly(3,4-ethylenedioxy-thiophene) (PEDOT) composite. PEDOT/h-CN hybrid film was directly deposited on glass carbon electrode (GCE) by in-situ electropolymerization. The incorporation of h-CN and PEDOT brought out enhanced electro-catalytic activity and additional binding sites for AA and AP, which could be ascribed to the synergetic effect between h-CN and PEDOT. Under the optimal experimental condition, the oxidation peak currents of AA and AP give linear response over the range of 4–20 μM, 20–1800 μM and 1–10 μM, 10–50 μM, respectively. The detection limit of the modified electrode was calculated to be 1.51 μM for AA and 0.49 μM for AP (S/N = 3). The electrochemical experiments also suggested that PEDOT/h-CN modified electrode was feasible practice for quantitative detection of AA and AP.
Metal-organic framework-derived Fe3C@NC nanohybrids as highly-efficient oxygen reduction electrocatalysts in both acidic and basic media J. Electroanal. Chem. (IF 3.235) Pub Date : 2018-07-17 Xinxin Yang, Xiaoli Hu, Xiuli Wang, Wei Fu, Tewodros Asefa, Xingquan He
Developing low-cost and high-performance non-precious metal catalysts (NPMCs) for oxygen reduction reaction (ORR) is of critical importance for commercialization of fuel cells. Herein, we report a NPMC consisting of Fe3C nanoparticles encapsulated in mesoporous N-doped carbon (N-C), which is synthesized by a simple two-step strategy comprising pyrolysis of a mixture of MIL-100(Fe) and dicyandiamide under inert atmosphere, followed by treatment of the product with acidic solution to leach removable Fe3C species from the material. Fe3C@NC-800 (the material prepared at 800 °C) exhibits superior electrocatalytic activity, high durability and excellent methanol tolerance for ORR, with catalytic performance comparable to that of commercial Pt/C in both alkaline and acidic media. Fe3C@NC-800's excellent catalytic activity and stability in ORR are due to its large BET surface area, its large total pore volume, its nitrogen dopants and the cooperative effects between the reactive functionalities in it as well as its excellent conductivity.
Investigation on the electrocatalytic activity of hierarchical flower like architectured Cu3SnS4 for hydrogen evolution reaction J. Electroanal. Chem. (IF 3.235) Pub Date : 2018-07-17 V. Maheskumar, P. Gnanaprakasam, T. Selvaraju, B. Vidhya
Copper tin sulphide (CTS) a prominent absorber layer in photovoltaics has been explored for its electrocatalytic activity in hydrogen evolution reaction (HER) by splitting of water. Here we report the preparation of CTS by two different methods such as ball milling (CTS (B)) and solvothermal (CTS (S)). Subsequently, due to the morphological difference an attempt has been made to explore the electrocatalytic activity between CTS (B) and CTS (S). As an electrocatalyst, it is found that CTS (S) with flower like architecture shows an enhanced electrocatalytic activity with a lower overpotential, a smaller Tafel slope (76 mV/dec) and much larger exchange current density than CTS (B). Furthermore CTS (S) exhibits high stability in acidic medium and meager degradation even after 2000 cycles towards HER catalytic activity. Enhanced catalytic activity, increased electrochemically accessible flower like morphology, high surface area and significantly improved electrochemical conductivity are observed at CTS (S).
Palladium-Prussian blue nanoparticles; as homogeneous and heterogeneous electrocatalysts J. Electroanal. Chem. (IF 3.235) Pub Date : 2018-07-17 Prem.C. Pandey, Shwarnima Singh, Alain Walcarius
We report herein a synthetic strategy based on the use of tetrahydrofuran hydroperoxide (THF-HPO) that allows controlled conversion of palladium ion and potassium ferricyanide into palladium nanoparticles (PdNP) and water soluble Prussian blue nanoparticles (PBNP) respectively. The results revealed that THF-HPO provide a medium to enable the transformation of 3-aminopropyltrimethoxysilane (3-APTMS) capped palladium ions into PdNP of desired nanogeometry viz. PdNP1 and PdNP2. The processability of these two types of nanomaterials enabled the formation of PB-PdNP1 and PB-PdNP2 having potentiality for use either as homogeneous suspension or in heterogeneous matrix. The results based on peroxidase mimetic activity, cyclic voltammetry and amperometry revealed the gradual improvement in analytical performances of as synthesized nanomaterials as a function of palladium size and has been characterized by TEM, HRSEM and EDX analysis.
Synchronous Synthesis and Sensing Performance of α-Fe2O3/SnO2 Nanofiber Heterostructures for Conductometric C2H5OH Detection Sens Actuators B Chem. (IF 5.667) Pub Date : 2018-07-17 Shuang Yan, Qingsheng Wu
A synthesis procedure based on single-capillary electrospinning and hard-template method was provided to synthesize hierarchical α-Fe2O3/SnO2 nanofibers. The samples exhibit unique microstructure where α-Fe2O3 nanoparticles were evenly decorated on three-dimensional SnO2 fibrous scaffold. During preparation, the α-Fe2O3 nanoparticles and SnO2 nanofibers were formed synchronously. Within the composite nanomaterials, the Fe/Sn content ratio can be adjusted by changing the diameter of SnO2 nanofibers backbone. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and nitrogen adsorption-desorption analysis were used to characterize the structure of the synthesized products. By loading α-Fe2O3 nanoparticles, the grain growth of SnO2 was effectively restrained during heat treatment in air. The optimum Fe/Sn content ratio of α-Fe2O3/SnO2 heterostructures with the highest sensitivity was obtained through ethanol sensing measurements. Compared to pure α-Fe2O3 and SnO2 nanofibers, the binary composite nanofibers exhibits not only enhanced ethanol sensing response, but also higher dependence of response to the change of ethanol concentration. The remarkable improvement of sensing performance can be attributed to the synergetic effect of the component phases. The influences of heterojunctions on the gas sensing properties of α-Fe2O3/SnO2 nanofibers were discussed.
pH assisted selective detection of Hg(II) and Ag(I) based on nitrogen-rich carbon dots Sens Actuators B Chem. (IF 5.667) Pub Date : 2018-07-17 Liang Luo, Pei Wang, Yuanhao Wang, Fu Wang
Novel nitrogen rich carbon dots were synthesized via a hydrothermal method by using with 2,4,6-triaminopyrimidine as the precursor. X-ray photoelectron spectroscopy showed that the carbon dots contained 41 at.% nitrogen; this is significantly higher than previously reported values for similar materials. When exposed to ultraviolet light, the carbon dots in solution emitted bright blue fluorescence, with a maximum quantum yield of 74.9%. The fluorescence was selectively quenched by Hg(II) at pH 6 and Ag(I) at pH 11, with detection limits of 11.4 and 10.3 nM, respectively. Analysis of the fluorescence lifetimes of the carbon dots showed that the fluorescence-quenching mechanism for Hg(II) differed from that for Ag(I). In analysis of lake water, the nitrogen-rich carbon dots were highly sensitive, and gave a wide linear range and satisfactory recovery. These results suggest that the carbon dots are suitable for use as novel metal ion probes for the selective detection of different ions at different pH values.
A dual-mode probe for colorimetric and fluorometric detection of cysteine based on phosphorus/nitrogen co-doped CQDs and gold nanorods Sens Actuators B Chem. (IF 5.667) Pub Date : 2018-07-17 Yanying Wang, Ruoxuan Liang, Wei Liu, Qingbiao Zhao, Xiaoyan Zhu, Li Yang, Ping Zou, Xianxiang Wang, Fang Ding, Hanbing Rao
In this study a novel method was developed for the fluorescent and colorimetric determination of cysteine (Cys). The fluorescent determination was designed based on surface plasmon-enhanced energy transfer (SPEET), and phosphorus/nitrogen co-doped CQDs (PNCQDs) were employed as the donor, of which the fluorescence was quenched by gold nanorods (AuNRs) (acceptor). For the colorimetric assay, under the catalytic effect of Fe3+, AuNRs were effectively etched by OH· that was generated by the Fenton reaction. The etch of the AuNRs lead to the decrease in the absorbance intensity, the blue shift of longitudinal surface plasmon resonance (LSPR) absorption peak of AuNRs as well as the fluorescence of PNCQDs recovery. However, Cys can suppress this etching reaction by coordination effect between hydrosulfide group (-SH) in Cys and Fe3+, leading to red shift of the LSPR absorption peak. Similarly, the fluorescence will change with the absorbance. The peak shift and the fluorescence change can be applied to monitor of Cys. Under the optimal operation conditions, highly sensitive determination of Cys was achieved, with the fluorescent detection limit of 1.2 nM and the colorimetric detection limit of 0.9 nM. The linearity of the system towards Cys was in the range of 0.005-25 μM. The highly sensitive determination of Cys in urine samples demonstrates that this method possesses high potential for on-site and visual detection of urine Cys.
Glutathione Detection Based on Peroxidase-Like Activity of Co3O4–Montmorillonite Nanocomposites Sens Actuators B Chem. (IF 5.667) Pub Date : 2018-07-17 Yan Gao, Kaili Wu, Hongyu Li, Wei Chen, Min Fu, Kang Yue, Xixi Zhu, Qingyun Liu
Co3O4 nanoparticles homogeneously anchored on montmorillonite (MMT) were synthesized via a facile hydrothermal method. Co3O4-MMT were demonstrated to possess intrinsic peroxidase- and weak oxidase-like activity, and employed as peroxidase mimics for the first time. The efficient catalytic activity of the Co3O4-MMT NCs may originate from the electron transfer among catalyst, TMB (3,3’,5,5’-tetramethylbenzidine) and H2O2. Furthermore, a sensitive colorimetric sensor for glutathione based on the peroxidase activity of Co3O4-MMT is proposed with a low detection limit of 0.088 µM. And the proposed method had been successfully applied in detecting GSH in human serum and reduced glutathione for injection solutions.
Facile Synthesis of Controllable TiO2 Composite Nanotubes via Templating Route: Highly Sensitive Detection of Toluene by Double Driving from Pt@ZnO NPs Sens Actuators B Chem. (IF 5.667) Pub Date : 2018-07-17 Wei Liu, Lin Xu, Kuang Sheng, Xiangyu Zhou, Xinran Zhang, Cong Chen, Biao Dong, Xue Bai, Lu Geyu, Hongwei Song
Electrospinning is an effective way to fabricate ultralong nanotubes with a large surface area. However, the nanotubes synthesized through this way suffer from difficult controlling of structural parameters. A facile strategy for constructing highly controllable Pt@ZnO nanoparticles (NPs) drive TiO2 nanotubes (NTs) (Pt@ZnO-TiO2 NTs) was developed in this work. First, the polystyrene electrospun nanofibers (~490 nm) containing Pt@zeolitic imidazolate framework-8 (ZIF-8) was fabricated as a self-sacrificial template and then was decorated by a thinner tetrabutyl orthotitanate layer through soaking. After annealing, the Pt@ZnO NPs were obtained due to the decomposition of Pt@ZIF-8 during calcination. The involving of ZIF-8 can effectively prevent the aggregation of Pt during heat treatment (~3 nm, monodispersed), and thus highly improves its catalyst property. When Pt@ZnO-TiO2 NTs were evaluated as a sensing material for toluene detection, the obtained sensors exhibited an enhanced sensing response (11.1 to 1 ppm toluene), faster response/recovery times (7.5 and 20.1 s) and a lower detection limit (23 parts per billion) during dynamic measurement, when compared to the pristine TiO2 and directly mixed Pt-TiO2 NTs. This was mainly attributed to the improved oxygen vacancy concentration in the NT composite and resistance modulation effect induced by the unique NT structure, as well as the well-dispersed and small-sized Pt catalyst.
An aqueous methylated chromenoquinoline-based fluorescent probe for instantaneous sensing of thiophenol with a red emission and a large Stokes shift Sens Actuators B Chem. (IF 5.667) Pub Date : 2018-07-17 Yani Geng, Huihui Tian, Liu Yang, Xingjiang Liu, Xiangzhi Song
A sensitive and selective fluorescent probe, MCQ-O-DNB, for the detection of thiophenol in aqueous media has been developed based on a methylated chromenoquinoline chromophore. This probe can instantaneously respond to thiophenol and reach to a balance within 2 min. In the detection process, this probe exhibited a large Stokes shift (108 nm) and a low detection limit (8.1 nM, based on S/N = 3). Importantly, practical application experiments demonstrated that this probe was able to detect thiophenol in real water samples and living cells.
Curcumin-based electrochemical sensor of amyloid-β oligomer for the early detection of Alzheimer’s disease Sens Actuators B Chem. (IF 5.667) Pub Date : 2018-07-17 Jieling Qin, Jin Su Park, Dong Gyu Jo, Misuk Cho, Youngkwan Lee
Amyloid β oligomer (AβO) is a promising biomarker with potential to diagnose the Alzheimer’s disease (AD). To detect the low level of AβO is highly desirable for the early diagnosis of AD. Here we describe the fabrication and sensing performance of curcumin based AβO sensor. Curcumin-Ni was electropolymerized on Ni foam substrate, and the surface resistance change of the poly(curcumin-Ni) electrode depending on AβO concentration was confirmed by electrochemical impedance spectroscopy. The impedance response of the curcumin based sensor showed a proportional relationship with the concentrations of AβO in the range from 0.001 to 5 nM. The feasibility of the sensor was verified by the detection of AβO in artificial cerebrospinal fluid. The proposed AβO sensor presents valuable information related to early diagnosis of AD.
Nano-molar to milli-molar level Ag (I) determination using absorption of light by ZnS QDs without organic ligand Sens Actuators B Chem. (IF 5.667) Pub Date : 2018-07-17 Rabindra Nath Juine, S. Amirthapandian, S. Dhara, A. Das
Despite of useful applications of Ag, it is hazardous to health and environment and hence early detection is required. Crystal defects influencing optical property is less likely utilized for Ag detection using prevalent UV-Vis technique. Quantum dots (QDs) ZnS prepared by soft chemical route are exploited for the detection of Ag+ in aqueous solution for nM to mM concentrations. UV-Vis and photoluminescence (PL) measurements reveal quantum confinement effect and presence of defects in ZnS nanoparticles (NPs). Controlled synthesis of ZnS NPs allows appearance of defects related peak at 400–550 nm in UV-Vis spectra. A plausible mechanism is presented and elucidated by XRD and PL studies for chemical interaction between ZnS with Ag+. The interaction affects prominently the defects related absorption of ZnS NPs and allows single step Ag+ detection in aqueous medium. This absorption method is extended to other ions (Na+, K+, Mg+, Ca+, Ba+) including ‘S’ prone heavy and toxic ions like Pb, Hg, and Cd. Among them, Ag+ shows the best response with ZnS NPs. This demonstration using a portable and cost effective technique with no organic component opens up possibility for other inorganic materials.
Fluorescent Cellulose Nanocrystals with Responsiveness to Solvent Polarity and Ionic Strength Sens Actuators B Chem. (IF 5.667) Pub Date : 2018-07-17 Weibing Wu, Ruyuan Song, Zhaoyang Xu, Yi Jing, Hongqi Dai, Guigan Fang
Fluorescent and stimuli-responsive cellulose nanocrystals (CNC) were prepared via covalent conjugation of a 1, 8-naphthalimide dye onto TEMPO-oxided CNC. The structural and morphological integrity of CNC were essentially not affected by the functionalizaiton, in spite of their relatively high dye content of 0.1±0.01 mmol g-1. The dye-labeled CNC show much higher fluorescence sensitivity to solvent permittivity and ion concentration compared to pure dye. The fluorescence emission of dye-labeled CNC is greatly enhanced when reducing solvent permittivity or increasing ionic strength. The magnified fluorescence responsiveness is attributed to the effect of aggregation-enhanced emission (AEE) based on the sensitive colloidal stability of CNC to medium conditions. Under high ionic strength and low solvent permittivity, the compressed double layers of CNC lead to space restriction and steric hindrance of dye groups, which limit the process of nonradiative transition. The aggregation of CNC triggered by the change of ion concentration was supported by dynamic light scattering (DLS) particle sizes and Zeta potential values. Owing to the special AEE effect, the fluorescent CNC are promising sensing nanomaterials for wide applications.
Research on moldy tea feature classification based on WKNN algorithm and NIR hyperspectral imaging Spectrochim. Acta. A Mol. Biomol. Spectrosc. (IF 2.88) Pub Date : 2018-07-17 Zhou Xin, Sun Jun, Wu Xiaohong, Lu Bing, Yang Ning, Dai Chunxia
In order to identify the moldy tea leaves in a fast and nondestructive way, a method involving wavelet coupled with k-nearest neighbor (WKNN) was proposed to select effective characteristic wavelengths in this paper. The hyperspectral imaging of 300 dried tea samples with 3 different mildew degrees (contrast check, mild moldy and severe moldy) were obtained using hyperspectral data acquisition device. Besides, food microbiological examination results showed that mold count and total numbers of colony increased with the increase of storage time, temperature and humidity. Roughness penalty smoothing (RPS) algorithm was used to preprocess the raw spectra. Afterwards, WKNN was applied to select the optimal wavelengths of spectral data by using db4, db6, sym5, sym7 as wavelet basis functions, respectively. In addition, five layers of wavelet decomposition were adopted based on different wavelet basis functions. Linear discriminant analysis (LDA) algorithm was used to build the classification models based on preprocessed spectra feature in characteristic wavelengths. The results showed that four optimal prediction models were optimal decomposition level in each wavelet basis function. In addition, the best performance model among all LDA models achieved an identification rate of 100% in the calibration set and 98.33% in the prediction set, in which db4 was used as wavelet basis function and the optimal wavelet decomposition level was 2. WKNN algorithm can effectively achieve the best wavelet decomposition layer and the best wavelengths. WKNN algorithm combined with NIR hyperspectral imaging technology can realize the effective wavelength extraction and classification of dried tea with different mildew degrees.
Polarized infrared spectroscopy imaging applied to structural analysis of bilirubin aggregate at liquid-liquid interface Spectrochim. Acta. A Mol. Biomol. Spectrosc. (IF 2.88) Pub Date : 2018-07-17 Yanfei Lu, Mingyang Zhai, Yongkang Zhu, Xiao Wang, Jianhua Yin
Fourier transform infrared spectroscopy imaging (FTIRSI) combined with spectral analysis and polarization approach was creatively used to investigate both structures of bilirubin (BR) precipitate and BR aggregate at liquid-liquid interface. It was found by spectral analysis that the internal hydrogen bonds of BR molecules all broke and the dihedral angles increased during the formation of BR aggregate at liquid-liquid interface. And the BR molecule might be of layer assembly along the long axis direction of CD half-group to form J-type aggregates, which could be parallel to the direction of the transition dipole moment of BR aggregate. The further study of polarized imaging/anisotropy revealed that the absorbance of 1570 and 1703 cm−1 bands of BR aggregate changed periodically at intervals of 90°, which were not shown in BR precipitate case, indicating that the CC of the corresponding lactam ring and the CO of the adjacent carboxyl groups formed ordered arrangement in BR aggregate. It also suggested that the two positions might be the active sites which J-type aggregates assembled on. The combined technique was firstly applied in interfacial aggregate research, which was helpful for further understanding and controlling the aggregation as well as structural transformation of BR molecules so as to decrease physiological hazard and facilitate the wide spread application in biomedicine.
Traditional versus advanced chemometric models for the impurity profiling of paracetamol and chlorzoxazone: Application to pure and pharmaceutical dosage forms Spectrochim. Acta. A Mol. Biomol. Spectrosc. (IF 2.88) Pub Date : 2018-07-17 Ahmed Sayed Saad, Amal Mahmoud Abou AlAlamein, Maha Mohammed Galal, Hala Elsayed Zaazaa
Traditional Partial Least Squares (PLS) and Advanced Artificial Neural Network (ANN) models were applied for the quantitative determination of paracetamol (PAR) and chlorzoxazone (CZX) together with their process-related impurities namely; 4-aminophenol (AP), 4‑chloroacetanilide (AC), 4‑nitrophenol (NP), 4‑chlorophenol (CP) and 2‑amino-4-chlorophenol (ACP). Both models were applied first to full spectrum data then the results were compared to those obtained after wavelength selection using Genetic Algorithm (GA). A 5-level 7-factor experimental design was used giving rise to 25 mixtures containing different proportions of the seven compounds. The calibration set was composed of 15 mixtures while 9 mixtures were used in the validation set to test the predictive ability of the suggested models. The four models PLS, ANN, GA-PLS and GA-ANN were successfully applied for the determination of PAR and CZX in their pure and pharmaceutical dosage form. One way ANOVA was carried out between the developed methods and the official ones for PAR and CZX and no significant difference was found. The four models can be easily applied for the determination of the selected drugs in quality control laboratories lacking expensive HPLC instruments.
A solid ionic Lactate biosensor using doped graphene-like membrane of Au-EVIMC-Titania nanotubes-Polyaniline Biosens. Bioelectron. (IF 8.173) Pub Date : 2018-07-17 Hongying Cheng, Cuiying Hu, Zhongling Ji, Wangcheng Ma, Hongxia Wang
Herein, a doped graphene-like membrane was designed, which was copolymerized to be a solid ionic biosensor by using titania nanotubes (TiNTs), polyaniline (PANI), EvimCl (1-ethyl-3-vinylimidazolium chloride, EVIMC) and chloroauric acid (HAuCl4). The structure of graphene-like arrangement and the copolymerization mechanism of the film were discussed in detail. Because of the high catalytic property, Lactate could be determined on the membrane catalyzed by lactate dehydrogenase (LDH) containing isocitrate dehydrogenase (NAD+), which was immobilized onto the film by electrostatic attraction. The electrochemical response on the LDH/Au-EVIMC-TiNTs-PANI/ITO was increased by twice than the LDH/TiNTs/PANI/ITO, and exhibited two linear responses within the concentration range from5.5×10−7M to 5.55×10−6M, and 5.55×10−6M to 3.33×10−3M, with a detection limit of 1.65×10−7 M (S / N=3). The interference study for other common coexistence such as uric acid and hemoglobin revealed that there was no overlapping signal for the detection of Lactate on the biosensor. The developed method proved the most stability in the determination of real blood samples, and the recoveries ranged from 96.7% to 105.8% with a satisfactory result.
A novel electrochemical biosensor for ultrasensitive detection of serum total bile acids based on enzymatic reaction combined with the double oxidation circular amplification strategy Biosens. Bioelectron. (IF 8.173) Pub Date : 2018-07-17 Gang Tian, Min Ding, Biao Xu, Yifan He, Wenjing Lyu, Mingchao Jin, Xiaoqing Zhang
Serum total bile acids (TBA) level is used as a sensitive and reliable index for hepatobiliary diseases in clinics. Herein, a novel electrochemical biosensor was fabricated using enzymatic reaction coupling with the double oxidation circular amplification strategy for the detection of human serum TBA. With the catalysis of 3α-hydroxysteroid dehydrogenase (3α-HSD), 3α-bile acids reacted specifically with nicotinamide adenine dinucleotide (NAD+). And then, the reduced nicotinamide adenine dinucleotide (NADH) was produced. After that, the NADH reacted with the electron mediator of tris(2,2'-bipyridine) ruthenium(Ⅲ) (Ru(bpy)33+), which was then transformed to Ru(bpy)32+. Ultimately, Ru(bpy)32+ was further oxidized to Ru(bpy)33+ under a certain voltage, which was detected by the chronoamperometry assay. The detection was performed using a disposable unmodified screen-printed carbon electrode (SPCE) without sample preparation. The proposed biosensor showed high sensitivity and accuracy with the linear range from 5.0 to 150.0 pmol/L in 106-fold dilution serum. The established method had a good correlation with the enzymatic cycling method (r = 0.9372, P < 0.001, n = 72) commonly used in clinic. The electrochemical biosensor is simple, ultrasensitive and without sample pretreatment, showing great potential for point-of-care testing (POCT) of serum TBA in clinical samples. In addition, the biosensor is cost-effective with a small volume of samples, especially suitable for those who have difficulties in blood collection, such as infants, children and some small animals.
Target-triggered signal-on ratiometric electrochemiluminescence sensing of PSA based on MOF/Au/G-quadruplex Biosens. Bioelectron. (IF 8.173) Pub Date : 2018-07-17 Kang Shao, Biru Wang, Axiu Nie, Ye Shiyi, Jing Ma, Zhonghua Li, Zhicheng Lv, Heyou Han
Signal-amplified ratiometric electrochemiluminescence (Sa-RECL) provides an attractive appoch to maximize signal-to-noise ratio through enhancing signals and eliminate interferences. In this work, we prepared a novel metal-organic framework (MOF)/Au/G-quadruplex as both quenchers and enhancers to fabricate a target-triggered ratiometric ECL sensor for high sensitive and accurate detection of prostatic specific antigen (PSA). The ratiometric ECL sensor using the dual-potential-dependent ECL emitters (quantum dots (QDs) and luminol) and MOF/Au/G-quadruplex not only achieved signal self-calibration but also realized cooperative amplification. After the sequential hybridization among of complementary DNA-QDs, PSA aptamer and pDNA-Au-Hemin-MIL-DNAzyme and the further competition of PSA, the pDNA-Au-Hemin-MIL-DNAzyme probe would keep away from the electrode surface, causing a switchover of their ECL signals from “off-on” state to “on-off” state. The ratiometric ECL aptasensor exhibits high-sensitive and accurate analytical performance toward PSA with a linear detection range from 0.5 to 500 ng mL-1 and a detection limit of 0.058 ng mL-1 (S/N = 3). The novel ratiometric ECL biosensor has been successfully applied to determine different serum samples of PSA, indicating its potential application in the clinical diagnosis.
Micro-Patterned Molecularly Imprinted Polymer Structures on Functionalized Diamond-Coated Substrates for Testosterone Detection Biosens. Bioelectron. (IF 8.173) Pub Date : 2018-07-17 Evelien Kellens, Hannelore Bové, Thijs Vandenryt, Jeroen Lambrichts, Jolien Dekens, Sien Drijkoningen, Jan D’Haen, Ward De Ceuninck, Ronald Thoelen, Tanja Junkers, Ken Haenen, Anitha Ethirajan
Molecularly imprinted polymers (MIPs) can selectively bind target molecules and can therefore be advantageously used as a low-cost and robust alternative to replace fragile and expensive natural receptors. Yet, one major challenge in using MIPs for sensor development is the lack of simple and cost-effective techniques that allow firm fixation as well as controllable and consistent receptor material distribution on the sensor substrate. In this work, a convenient method is presented wherein microfluidic systems in conjunction with in situ photo-polymerization on functionalized diamond substrates are used. This novel strategy is simple, efficient, low-cost and less time consuming. Moreover, the approach ensures a tunable and consistent MIP material amount and distribution between different sensor substrates and thus a controllable active sensing surface. The obtained patterned MIP structures are successfully tested as a selective sensor platform to detect physiological concentrations of the hormone disruptor testosterone in buffer, urine and saliva using electrochemical impedance spectroscopy. The highest added testosterone concentration (500 nM) in buffer resulted in an impedance signal of 10.03 ± 0.19% and the lowest concentration (0.5 nM) led to a measurable signal of 1.8 ± 0.15% for the MIPs. With a detection limit of 0.5 nM, the MIP signals exhibited good linearity between 0.5 nM to 20 nM concentration range. Apart from the excellent and selective recognition offered by these MIP structures, they are also stable during and after the dynamic sensor measurements. Additionally, the MIPs can be easily regenerated by a simple washing procedure and are successfully tested for their reusability.
Distinguishment of populated metastatic cancer cells from primary ones based on their invasion to endothelial barrier by biosensor arrays fabricated on nanoroughened Poly(methyl methacrylate) Biosens. Bioelectron. (IF 8.173) Pub Date : 2018-07-17 Mohammad Saeed Nikshoar, Safoora Khosravi, Mojtaba Jahangiri, Ashkan Zandi, Zohreh sadat Miripour, Shahin Bonakdar, Mohammad Abdolahad
Determining the migratory and invasive capacity of cancer cells as well as clarifying the underlying mechanisms are most relevant for developing biosensors in cancer diagnosis, prognosis, drug development and treatment. Intravasation of metastatic cells into blood stream initiated by their invasion to vascular layer would be a significant characteristic of metastasis. Many types of biochemical and bioelectrical sensors were developed for early detection of metastasis. The simplicity of the setup, the ease of the readout, detection of the trace of rare metastatic cells and the feasibility to perform the assay with standard laboratory equipment are some of the challenges limiting the usability of the sensors in tracing the metastasis. Here we describe a biosensor based on recently reported metastatic diagnosis assay; Metas-Chip, with the assistance of nanoroughened Poly-methyl methacrylate (PMMA) layer to diagnose populated metastatic breast cells from primary cancerous ones. Retraction and detachment of Human Umbilical Vein Endothelial Cells (HUVECs) invaded by metastatic cells as a recently found phenomena is the mechanism of the action. A population of HUVECs would be detached from the gold microelectrodes, patterned on nanoroughened surface, which would lead to large changes in impedance. Here, applying biocompatible and patternable nanoroughened surface instead of using adhesive layers which might produce electrical noises resulted in great sensitivity and detectivity of the sensor. Apart from the tight interaction between endothelial cells and nanocontacts of the electrodes, using low concentration (10%) of tumor cells in this invasion assay, might enhance its application in clinical trials.
Hairpin DNA-AuNPs as molecular binding elements for the detection of volatile organic compounds Biosens. Bioelectron. (IF 8.173) Pub Date : 2018-07-17 Marcello Mascini, Sara Gaggiotti, Flavio Della Pelle, Joseph Wang, José M. Pingarrón, Dario Compagnone
Hairpin DNA (hpDNA) loops were used for the first time as molecular binding elements in gas analysis. The hpDNA loops sequences of unpaired bases were studied in-silico to evaluate the binding versus four chemical classes (alcohols, aldehydes, esters and ketones) of volatile organic compounds (VOCs). The virtual binding score trend was correlated to the oligonucleotide size and increased of about 25% from tetramer to hexamer. Two tetramer and pentamer and three hexamer loops were selected to test the recognition ability of the DNA motif. The selection was carried out trying to maximize differences among chemical classes in order to evaluate the ability of the sensors to work as an array. All oligonucleotides showed similar trends with best binding scores for alcohols followed by esters, aldehydes and ketones. The seven ssDNA loops (CCAG, TTCT, CCCGA, TAAGT, ATAATC, CATGTC and CTGCAA) were then extended with the same double helix stem of four base pair DNA (GAAG to 5’ end and CTTC to 3’ end) and covalently bound to gold nanoparticles (AuNPs) using a thiol spacer attached to 5’ end of the hpDNA. HpDNA-AuNPs were deposited onto 20 MHz quartz crystal microbalances (QCMs) to form the gas piezoelectric sensors. An estimation of relative binding affinities was obtained using different amounts of eight VOCs (ethanol, 3-methylbutan-1-ol, 1-pentanol, octanal, nonanal, ethyl acetate, ethyl octanoate, and butane-2,3-dione) representative of the four chemical classes. In agreement with the predicted simulation, hexamer DNA loops improved by two orders of magnitude the binding affinity highlighting the key role of the hpDNA loop size. Using the sensors as an array a clear discrimination of VOCs on the basis of molecular weight and functional groups was achieved analyzing the experimental with principal components analysis (PCA) demostratng that HpDNA is a promising molecular binding element for analysis of VOCs.
Measurements of Atmospheric Proteinaceous Aerosol in the Arctic Using a Selective UHPLC/ESI-MS/MS Strategy J. Am. Soc. Mass Spectrom. (IF 2.869) Pub Date : 2018-07-17 Farshid Mashayekhy Rad, Javier Zurita, Philippe Gilles, Laurens A. J. Rutgeerts, Ulrika Nilsson, Leopold L. Ilag, Caroline Leck
In this article, an analytical methodology to investigate the proteinaceous content in atmospheric size-resolved aerosols collected at the Zeppelin observatory (79 °N, 12 °E) at Ny Ålesund, Svalbard, from September to December 2015, is proposed. Quantitative determination was performed after acidic hydrolysis using ultrahigh-performance liquid chromatography in reversed-phase mode coupled to electrospray ionization tandem mass spectrometry. Chromatographic separation, as well as specificity in the identification, was achieved by derivatization of the amino acids with N-butyl nicotinic acid N-hydroxysuccinimide ester prior to the analysis. The chromatographic run was performed within 11 min and instrumental levels of detection (LODs) were between 0.2 and 8.1 pg injected on the column, except for arginine which exhibited an LOD of 37 pg. Corresponding method LODs were between 0.01 and 1.9 fmol/m3, based on the average air sampling volume of 57 m3. The sum of free amino acids and hydrolyzed polyamino acids was shown to vary within 6–2914 and 0.02–1417 pmol/m3 for particles in sizes < 2 and 2–10 μm in equivalent aerodynamic diameter, respectively. Leucine, alanine, and valine were the most abundant among the amino acids in both aerosol size fractions. In an attempt to elucidate source areas of the collected aerosols, 5- to 10-day 3D backward trajectories reaching the sampling station were calculated. Overall, the method described here provides a first time estimate of the proteinaceous content, that is, the sum of free and polyamino acids, in size-resolved aerosols collected in the Arctic.
Combined Short-Term Glucose Starvation and Chemotherapy in 3D Colorectal Cancer Cell Culture Decreases 14-3-3 Family Protein Expression and Phenotypic Response to Therapy J. Am. Soc. Mass Spectrom. (IF 2.869) Pub Date : 2018-07-17 Monica M. Schroll, Katelyn R. Ludwig, Gabriel J. LaBonia, Emily L. Herring, Amanda B. Hummon
Short-term glucose starvation prior to chemotherapy has the potential to preferentially weaken cancer cells, making them more likely to succumb to treatment, while protecting normal cells. In this study, we used 3D cell cultures of colorectal cancer and assessed the effects of short-term glucose starvation and chemotherapy compared to treatment of either individually. We evaluated both phenotypic changes and protein expression levels. Our findings indicate that the combined treatment results in more significant phenotypic responses, including decreased cell viability and clonogenicity. These phenotypic responses can be explained by the decreased expression of LDHA and 14-3-3 family proteins, which were found only in the combined treatment groups. This study indicates that short-term glucose starvation has the potential to increase the efficacy of current cancer treatment regimes.
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 nanosystem composed of upconversion nanoparticles and N, N-diethyl-p-phenylenediamine for fluorimetric determination of ferric ion Microchim. Acta (IF 5.705) Pub Date : 2018-07-17 Min Chen, Felix Y. H. Kutsanedzie, Wu Cheng, Akwasi Akomeah Agyekum, Huanhuan Li, Quansheng Chen
A system composed of upconversion nanoparticles (UCNPs) and N,N-diethyl-p-phenylenediamine (EPA) is shown to be a useful probe for highly sensitive and selective fluorometric determination of ferric ion. The fluorescence of the UCNPs (under the 980 nm excitation) has peaks at 546, 657, 758 and 812 nm. EPA is readily oxidized by Fe(III) to generate a dye with a peak at 552 nm. This causes an inner filter effect on the fluorescence peaks at 546 nm, whereas the emissions at 657, 758 and 812 nm remained unchanged. Therefore, the iron concentration can be quantified by measurement of the ratio of fluorescence at 546 and 758. Under optimal condition, the ratio drops linearly in the 0.25 to 50 μM. Fe(III) concentration ranges, with a detection limit of 0.25 μM. The method is highly selective and was applied to the analysis of spiked samples (wastewater) where it gave recoveries of between 100.9 and 107.3%; and RSD values between 0.8 and 1.4%. Results are approximately the same as those obtained by AAS.
Aptamer based voltammetric biosensor for Mycobacterium tuberculosis antigen ESAT-6 using a nanohybrid material composed of reduced graphene oxide and a metal-organic framework Microchim. Acta (IF 5.705) Pub Date : 2018-07-17 Linlin Li, Yonghua Yuan, Yongjie Chen, Pu Zhang, Yan Bai, Lijuan Bai
The 6-kDa early secretory antigenic target referred to as ESAT-6 is a virulence factor secreted by Mycobacterium tuberculosis (MTB). This work describes a voltammetric aptasensor for ultrasensitive detection of ESAT-6. Reduced graphene oxide doped with metal-organic framework (MOF-rGO) was deposited on a glassy carbon electrode (GCE). This increases the immobilization of electroactive Toluidine Blue (TB) and facilitates the electron transfer from TB to the modified GCE. Platinum/gold core/shell (Pt@Au) nanoparticles were used to assemble thiolated ESAT-6 binding aptamer (EBA) on a modified electrode and to further amplify the response to TB. The modified GCE, typically operated at −0.36 V (vs. SCE), has a linear response in 1.0 × 10−4 to 2.0 × 102 ng⋅mL-1 ESAT-6 concentration range, and the limit of detection (LOD) for ESAT-6 is as low as 3.3 × 10−5 ng⋅mL-1. It exhibits satisfactory specificity and reproducibility when analyzing spiked human serum.
Algorithm for optimal denoising of Raman spectra Anal. Methods (IF 2.073) Pub Date : 2018-07-17 Sinead Barton, Bryan M Hennelly, Tomas Ward
Raman spectroscopy has been demonstrated to have diagnostic potential in areas such as urine and cervical cytology, whereby different disease groups can be classified based on subtle differences in the cell or tissue spectra using various multi-variate statistical classification tools. However, Raman scattering is an inherently weak process, which often results in low signal to noise ratios, thus limiting the method's diagnostic capabilities under certain conditions. A common approach for reducing the experimental noise is Savitzky-Golay smoothing. While this method is effective in reducing the noise signal, it has the undesirable effect of smoothing the underlying Raman features, compromising their discriminative utility. Maximum Likelihood Estimation is a method for estimating the parameters of a statistical model given an available dataset and a priori knowledge of the model type. In this paper, we demonstrate how Savitzky-Golay smoothing may be enhanced with Maximum Likelihood Estimation in order to prevent significant deviation from the 'true' Raman signal yet retain the robust smoothing properties of the Savitzky-Golay filter. The algorithm presented here is demonstrated to have a lower impact on Raman spectral features at known spectral peaks while providing superior denoising capabilities, when compared with established smoothing algorithms; artificially noised databases and experimental data are used to evaluate and compare the performance of the algorithms in terms of the signal to noise ratio. The proposed method is demonstrated to typically provide at least a 50% increase in the signal to noise ratio when compared to the raw data, and consistently out-performs two alternative smoothing filters. MATLAB code is provided in the appendix.
TransFEr: a new device to measure the transfer of volatile and hydrophobic organic chemicals across an in vitro intestinal fish cell barrier Anal. Methods (IF 2.073) Pub Date : 2018-07-17 Hannah Schug, Frederic Begnaud, Christian Debonneville, Fabienne Berthaud, Sylvia Gimeno, Kristin Schirmer
Transfer of compounds across cellular barriers is a critical step of compound uptake into organisms. Using in vitro barrier systems to evaluate such transfer is attractive because of the higher throughput and reduced resource needs compared to animal studies. Thus far, however, studying the transfer of hydrophobic and volatile compounds was hampered by the unavailability of in vitro exposure systems that allow for stable and predictable chemical exposure concentrations. To overcome this limitation, we constructed a novel exposure chamber, TransFEr, and tested it with an in vitro epithelial barrier model using the rainbow trout (Oncorhynchus mykiss) intestinal cell line, RTgutGC. Key features of the chamber are its closed design and rotatable silicon segments, which can serve for chemical dosing and sampling. Using the fragrance Damascone beta (logKOW:3.7, logHLC:-3.9) as a pilot chemical, we were able to demonstrate that our exposure chamber provides for stable chemical exposure concentrations and full mass balance. The RTgutGC epithelium served as barrier for Damascone beta transfer, which we attribute to chemical retention and biotransformation in the intestinal cells. Nevertheless, substantial transfer of the chemical across the epithelium occurred. When a chemical sink, i.e. a silicon segment, was included in the basolateral chamber to mimic blood constituents binding in vivo, transfer was about three-fold enhanced. We suggest that the presented methodology can help to obtain insights into chemical uptake mechanisms via the intestinal or other epithelia of fish and other animals for hydrophobic and volatile chemicals.
Quantification of Estrogens in Infant Formula by Isotope Dilution Liquid Chromatography-tandem Mass Spectrometry Anal. Methods (IF 2.073) Pub Date : 2018-07-17 Shuan Liu, Xiaomin Li, Yingchen Zhao, Xiong Yin, Qing He Zhang, Xiuqin Li, Guangshi Tang, Hongmei Li
The steroid estrogens, such as, estrone (E1), 17β-estradiol (E2) and estriol (E3), have shown potentially adverse effects on the health of children. Consequently, it is highly desirable to develop the detection approaches for rapid and accurate determination of steroid estrogens in infant formula. In this study, a robust method based on isotope dilution liquid chromatography-tandem mass spectrometry (ID LC-MS/MS) was developed to simultaneously measure E1, E2 and E3 in infant formula with no need for derivatization step. The desired simplicity, accurateness and specificity were achieved via facile sample pretreatment process, including protein precipitation and clean-up steps. The limits of quantification was 0.0025, 0.005 and 0.005 μg kg-1 for E1, E2 and E3, respectively. Besides, recovery of 92.3%-102.7% was obtained with relative standard deviation less than 6%. Furthermore, both accurate values for the target analytes ranging from 0.005 to 50 μg kg-1 and corresponding relatively expanded uncertainty less than 12% were obtained using the ID LC-MS/MS method. More importantly, the approach is highly sensitive, selective and accurate in screening the estrogens in real infant formula samples. Thus, it could be convenient for large-scale application due to its derivatization-free and simplicity in sample preparation.
A novel fluorescence sensing method based on quantum dot-graphene and molecular imprinting technique for the detection of tyramine in rice wine Anal. Methods (IF 2.073) Pub Date : 2018-07-17 Qinghua Wang, Dongdong Zhang
Tyramine, an important biogenic amine, occurs in high amounts in certain processed food products that can cause adverse health effects in people. In this study, we developed a simple method to produce a molecularly imprinted fluorescence sensor with high sensitivity and selectivity for tyramine. The reverse microemulsion method was applied to prepare a carrier material, hydrophobic CdSe/ZnS quantum dots (QDs) sensitized with carboxylated graphene (Gra), which was added to the reaction for synthesizing molecularly imprinted polymers (MIPs) using 3-mercaptopropyltriethoxysilane(MPTES) as the functional monomer and tetraethylorthosilicate (TEOS) as the crosslinking agent in the presence of tyramine as the target molecule. The novel sensing material, Gra-QDs@MIPs, was selective for tyramine and generated a concentration-dependent fluorescence signal. Under optimized conditions, the limit of detection was 0.021 mg•L-1and the linear range of detection was 0.07–12 mg•L-1. Importantly, we tested the performance of the Gra-QDs@MIPs with real-world samples by demonstrating that it selectively detected around 0.08 or 2 mg•L-1 of tyramine in spiked rice wine samples. Hence, the described molecularly imprinted fluorescence sensor for tyramine could serve as a prototype for developing MIP-based assays for food analysis.
Microfluidics in coagulation monitoring devices: a mini review Anal. Methods (IF 2.073) Pub Date : 2018-07-16 Leanne F. Harris, Anthony J. Killard
Simultaneous HS-SPME GC-MS determination of short chain fatty acids, trimethylamine and trimethylamine N-oxide for gut microbiota metabolic profile Talanta (IF 4.244) Pub Date : 2018-07-17 Jessica Fiori, Silvia Turroni, Marco Candela, Patrizia Brigidi, Roberto Gotti
Trimethylamine (TMA), trimethylamine-N-oxide (TMAO) and short chain fatty acids (SCFAs), as acetic, propionic, butyric and valeric acids are among the most important products of the gut microbiota (GM) metabolism. The present study is aimed at the determination of TMA, TMAO and SCFAs by a double step headspace-solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) analysis, allowing the simultaneous quantitation of both the acidic and basic metabolites in faecal samples. TMAO amount was evaluated after its reduction to TMA by using Fe(II)-EDTA complex as a reagent. Under the fully validated experimental conditions, adequate sensitivity (LOQ 0.008–0.23 µmoL g−1), good accuracy (79 – 110%) and precision (CV% < 11%) were achieved for all the target analytes. The presented method is successfully applied to the quantitation of the considered gut metabolites in faecal samples from Italian healthy volunteers.
An electrochemical biosensor for the rapid detection of erythropoietin in blood Talanta (IF 4.244) Pub Date : 2018-07-17 Waleed A. Hassanain, Arumugam Sivanesan, Emad. L. Izake, Godwin A. Ayoko
A label free electrochemical detection method for the rapid detection of recombinant human erythropoietin (rhuEPO) has been developed. In this method, we modified the rhuEPO structure for its direct sensing without using a complex signal amplification strategy. The protein was selectively extracted from blood plasma sample using target-specific magnetic beads. After releasing rhuEPO from the magnetic beads, its disulfide bonds were electrochemically reduced and the protein was spontaneously assembled onto a nanostructured gold electrode via Au-S bonds formation. For electrochemical quantification, the reduced protein was desorbed from the electrode surface using differential pulse voltammetry (DPV). The desorption current was proportional to the concentration of rhuEPO in the range 1 pM – 1000 pM. By cross-validating against ELISA, we found a 104.85 ± 3.35% agreement between the results obtained using the electrochemical biosensor and ELISA. Therefore the developed method has a strong potential for the sensitive detection of rhuEPO doping in sports as well as its rapid screening and pathology labs.
Target Induced Aggregation of Ce(III)-based Coordination Polymer Nanoparticles for Fluorimetric Detection of As(III) Talanta (IF 4.244) Pub Date : 2018-07-17 Jia-Le Yang, Yan-Hong Yuan, Ru-Ping Liang, Jian-Ding Qiu
As(III) is the most harmful substance of all over 20 kinds of arsenic compounds. In addition, the trivalent oxidation state of arsenic is not stable, which can be oxidized to pentavalent arsenic. Thus, it is attractive and challenging to sensitively and selectively monitor As(III) concentration, rather than As(V) concentration, in water. However, most of detection techniques suffer from the inability to distinguish As(III) and As(V), or even need specialized personnel and additional equipment. Herein, novel luminescent Ce(III)-based coordination polymer nanoparticles (Ce-CPNs) have been proposed for selective detection of As(III). The Ce-CPNs are dispersive and show a fluorescence peak at 353 nm under excitation at 280 nm. With the presence of As(III), aggregation of Ce-CPNs occurs, resulting in quenching of the fluorescent Ce-CPNs due to the aggregation-caused π-π stacked layers of Ce-CPNs. Under optimal conditions, the detection limit for As(III) is down to 0.7 ppb. In addition, the Ce-CPNs are selective for As(III) over other ions and has been successfully applied for fluorescence sensing of As(III) in environmental water samples.
Photometric and fluorometric alkaline phosphatase assays using the simplest enzyme substrates Talanta (IF 4.244) Pub Date : 2018-07-17 Justyna Bzura, Marta Fiedoruk-Pogrebniak, Robert Koncki
In this contribution a highly cost-effective flow analysis system for determination of alkaline phosphatase (ALP) activity is presented. This fully-mechanized bioanalytical system is based on economic solenoid micropumps and microvalves (powered and actuated by Arduino microcontroller) and extremely cheap dedicated optoelectronic flow-through detectors allowing absorbance and fluorescence measurements. The detection schemes for ALP assaying realized in this system are based on orthophosphate determination. For the detection of these ions formed in the course of enzymatic conversion a molybdate method requiring only common and inexpensive chemicals is utilized. Thus, for the enzymatic assays the simplest not-chromogenic/not-fluorogenic ALP substrates can be applied. Such approach results in the use of low-cost reagents for ALP assays, whereas the mechanization of assay causes low consumption of reagents as well as samples. In the course of reported investigations six ALP substrates were examined and the most promising results have been obtained for the inorganic compound – monofluorophosphate (MFP). The obtained linear ranges of absorbance and fluorescence measurements are 100–600 U·L−1 and 30-30/30–100 U·L−1, with sensitivities of 0.7 mV·L−1·U−1 and 2.3/1.0 mV·L−1·U−1, respectively. The calculated limits of detection are 5.1 U·L−1 (photometry) and 0.9 U·L−1 (fluorometry). The throughputs of the developed system are 13 and 12 samples/h for photometric and fluorimetric detections, respectively. To demonstrate the practical utility of the developed bioanalytical system the ALP assays in complex matrix samples have been carried out. The results of ALP activity determination in serum samples are well-correlated with those obtained using reference method recommended for routine clinical analysis.
Mercury fractionation in marine macrofauna using thermodesorption technique: method and its application Talanta (IF 4.244) Pub Date : 2018-07-17 Agnieszka Jędruch, Magdalena Bełdowska, Urszula Kwasigroch, Monika Normant-Saremba, Dominika Saniewska
Mercury (Hg) is one of the most dangerous elements, and its toxicity and ability to accumulate in organisms depend on its chemical form. There are numerous methods of Hg speciation analysis, out of which the least expensive and the least time-consuming one is thermodesorption. The method has been successfully used for the analysis of abiotic samples – soils and sediments. The aim of this study was to verify whether the simplified thermodesorption method can be used in the analysis of the tissues of animal organisms from different trophic levels. Hg fractionation analyses were performed on a DMA-80 analyser (Milestone, Italy). The results presented in this paper are the first published data on Hg fractionation by thermodesorption method in animal tissues. The study showed that the 5-step thermodesorption method can be applied to various types of environmental matrices, which makes it universal. This method is of great importance in terms of estimating the Hg uptake and transfer in the trophic chain, and also enables the assessment of global Hg circulation in the environment. The presented method does not require previous digestion of samples or the use of expensive reagents. It can also be used for the preliminary selection of samples for MeHg analysis. The results obtained by this 5-step fractionation could be comparable with different research, conducted using other Hg analysers.
Total risk of a false decision on conformity of an alloy due to measurement uncertainty and correlation of test results Talanta (IF 4.244) Pub Date : 2018-07-17 Ilya Kuselman, Francesca R. Pennecchi, Ricardo J.N.B. da Silva, D. Brynn Hibbert, Elena Anchutina
Total risk (probability) of a false decision on conformity of an alloy due to measurement uncertainty and correlation of test results is quantified. As an example, a dataset of test results of a PtRh alloy is studied when contents of four components of the alloy composition are under control. There are specification limits for contents of 1) Pt and 2) Rh; 3) three precious impurities - Au, Ir and Pd, and 4) eight impurities, both precious Au, Ir, Pd, and non-precious Fe, Pb, Si, Sn, Zn. Test results of 100 batches of the alloy produced at the same plant, obtained by X-ray fluorescence and optical atomic emission spectrometry methods at the plant laboratory, were in the dataset. The Pt content was tested based on the mass balance. Measurement uncertainties of the test results are estimated summarizing data of validation reports of the measurement procedures for different elements/analytes. These test results are correlated because of the natural chemical origin of the raw materials used in the alloy production and mass balance constraints. Correlations between test results for two pairs of the components (Pt vs. Rh, and the three vs. the eight impurities) were strong. To assess the correlation effects on the total risk, the study was performed for two scenarios considering 1) correlated test results for all four components, and 2) practically uncorrelated test results for two components only - Rh and the eight impurities. A matrix Bayesian approach was applied for total risk evaluation, where the observed correlations are taken into account within the experimental correlation matrix. This matrix influenced all subsequent multivariate calculation results. It was shown that simplification of the testing by reducing the number of components under control leads to a significant increase of the probability of a false decision on conformity of an alloy batch randomly drawn from a statistical population of such batches. Core of the developed R code, used for the risk calculations, is presented.
A novel fluorimetric sensing strategy for highly sensitive detection of phytic acid and hydrogen peroxide Anal. Chim. Acta (IF 5.123) Pub Date : 2018-07-17 Zhengyi Qu, Weidan Na, Yixin Nie, Xingguang Su
In this paper, we developed a sensitive sensor for phytic acid (PA) and hydrogen peroxide (H2O2) detection based on glutathione-functionalized graphene quantum dots (GQDs@GSH). The fluorescence of GQDs@GSH was found to be effectively quenched by Fe3+ ions via photo-induced electron transfer (PET) process. Upon the addition of PA to GQDs@GSH/Fe3+ system, the fluorescence of GQDs@GSH was significantly restored due to the strong chelating and reducing ability of PA, Fe3+ ions could be reduced to Fe2+ ions by PA and formed PA/Fe2+ complex. Therefore, the “off–on” fluorescence method was constructed to detect PA by using GQDs@GSH/Fe3+ as a fluorescent probe. Furthermore, the method can be used for the detection of H2O2. H2O2 can destroy the chelate structure of PA/Fe2+, release Fe2+ ions and oxidize Fe2+ ions to produce Fe3+ ions, leading to the fluorescence quenching of GQDs@GSH again. Under optimal conditions, the fluorescence sensing platform showed good linear relationship between the relative fluorescence intensity I/I0 and the concentration of PA and H2O2 in the range of 0.05 to 3 μmol L-1 and 0.5 to 10 μmol L-1, respectively. The detection limits of PA and H2O2 were 14 nmol L-1 and 0.134 μmol L-1, respectively. Furthermore, the fluorescence assay method was also applied in real sample analysis and satisfactory results were obtained.
Development of a cobalt(II)phthalocyanine- MWCNT modified carbon paste electrode for the detection of polyunsaturated fatty acids Anal. Chim. Acta (IF 5.123) Pub Date : 2018-07-17 Anita Jerković, Sandra Abou-Ahmed, Paul Ertl, Barbara Stoeßl, Vanessa Lengauer, Anchalee Samphao, Kurt Kalcher, Gerd Leitinger, Stefan Wernitznig, Astrid Ortner
In this work the development of an electrochemical sensor for the determination of polyunsaturated fatty acids (PUFAs), in particular linoleic acid, in commercially available safflower oil as complex matrix is described. The sensor consists of a carbon paste electrode with cobalt (II)phthalocyanine, Co(II)Pc, as mediator and multiwalled carbon-nanotubes (MWCNT) as nanomaterial. As carrier medium a sodium borate buffer (0.1 M, pH 9) was used. PUFAs were detected at a working voltage of 0.35 - 0.45 V (vs. Ag/AgCl). The sensor development was carried out in a batch system with differential pulse voltammetry (DPV) and cyclic voltammetry (CV). Sensor specification was tested by using various fatty acids (stearic acid, oleic acid, linoleic acid, linolenic acid and arachidonic acid) as well as esterified fatty acids, resulting in a specific applicability towards PUFAs, especially linoleic acid (LAH). The optimized sensor was applied in a flow injection analysis system (FIA) for the analysis of PUFAs in complex matrix. Linoleic acid was used as standard substrate to determine the analytical parameters. The linearity ranges between 7.5 and 200 μg mL-1 LAH, while the limit of detection was determined to be 2.5 μg mL-1 and the limit of quantification is approximately 7.5 μg mL-1 LAH. The LAH content was successfully detected in commercially available safflower oil via standard addition method and the results could be confirmed by a reference method. The PUFA content was calculated as LAH-equivalent.
Non-SELEX Isolation of DNA Aptamers for the Homogeneous-Phase Fluorescence Anisotropy Sensing of Tau Proteins Anal. Chim. Acta (IF 5.123) Pub Date : 2018-07-17 Samuele Lisi, Emmanuelle Fiore, Simona Scarano, Emanuela Pascale, Yannik Boehman, Frederic Ducongé, Sabine Chierici, Maria Minunni, Eric Peyrin, Corinne Ravelet
Herein, we report for the first time the isolation of DNA aptamers directed against the whole tau protein, an important Alzheimer's disease (AD) biomarker. Non-SELEX approach based on the capillary electrophoresis partitioning technique was employed to isolate a high-affinity DNA sequence pool towards the target in only three rounds and one working day. High-throughput sequencing was next performed and the recognition ability of five selected aptamers was preliminary evaluated by surface plasmon resonance using the protein target immobilized on the chip. Finally, the analytical potential of the most affine aptamer was demonstrated through the design of a homogeneous-phase fluorescence anisotropy assay. This DNA aptamer was found to be able to recognize not only the whole τ-441 but also the τ-381, τ-352, τ-383 isoforms. The sensing platform allowed the determination of these four targets with a detection limit of 28 nM, 3.2 nM, 6.3 nM and 22 nM, respectively.
Study of endocrine disrupting compound release from different medical devices through an on-line SPE UHPLC-MS/MS method Anal. Chim. Acta (IF 5.123) Pub Date : 2018-07-17 Fabio Gosetti, Bianca Bolfi, Elisa Robotti, Marcello Manfredi, Marco Binotti, Federica Ferrero, Gianni Bona, Emilio Marengo
The paper deals with the development of an online UHPLC-MS/MS method for the identification and determination of 25 Endocrine Disrupting Chemicals (EDCs) belonging to different chemical classes (perfluorochemicals, bisphenols, alkylphenols, phthalates, and parabens). The study regards the possible EDC migration from different medical devices of diverse materials used in the routine hospitals for blood sampling or for the parenteral nutrition therapies. In order to evaluate the release of EDCs, the equipment used for blood sampling (syringes, butterfly, cannula-needle, microcapillary tube) was put in contact with a physiological solution at a prefixed time. As regards the migration tests carried out on the medical devices used in the parenteral nutrition therapy (infusion tubes, venous catheters), the catheters were undergone to internal contact with parenteral solution and external contact with physiological one, whereas the infusion tubes were subjected only to internal migration test with parenteral solution. The results demonstrated the released of some ECDs (such as parabens at the concentration of few pg mL−1, diethylphthalate and dibutylphthlate at ng mL−1, level), when using physiological solution as the leaching agent. In addition, the presence of a PFOS structural isomer was found at 29.0 ng mL-1: this compound was released in part from the infusion tubes and mostly from the venous catheters, particularly from silicone ones. Using a more lipophilic solution, such as parenteral preparations, a greater amount of EDCs was released, among which also the diethylhexylphthalate that was quantified in all the investigated devices (without highlighting particular trends or migration from PVC devices), but its concentration remained always lower than imposed maximum threshold limit on medical device of 0.1% w/w. The releases from the infusion tubes of the same materials (polyethylene) from different manufacturers are very comparable, whereas the catheter of silicone releases greater amount of EDCs than that of polyurethane.
Evaluation of two-step liquid-liquid extraction protocol for untargeted metabolic profiling of serum samples to achieve broader metabolome coverage by UPLC-Q-TOF-MS Anal. Chim. Acta (IF 5.123) Pub Date : 2018-07-17 Rui Liu, Jing Chou, Shaoying Hou, Xiaowei Liu, Jiaying Yu, Xinshu Zhao, Ying Li, Liyan Liu, Changhao Sun
Untargeted metabolomics studies aim to extract a broad coverage of metabolites from biological samples, which largely depends on the sample preparation protocols used for metabolite extraction. The aim of this study was to evaluate a comprehensive sample pretreatment strategy using two-step liquid-liquid extraction to achieve broader metabolome coverage by ultra-high-performance liquid chromatography coupled with electrospray ionization time-of-flight mass spectrometry (UPLC-Q-TOF-MS). We compared four protocols: (A) methanol protein precipitation, (B) Ostro 96-well plates, (C) two-step extraction protocol of CHCL3-MeOH followed by MeOH-H2O, and (D) two-step extraction protocol of CH2CL2-MeOH followed by MeOH-H2O. The number of extracted features, reproducibility and recovery were the major criteria for evaluation. Our results demonstrated that Protocols B, C and D, with approximately similar number of features, extracted more features than Protocol A. Protocols C and D appeared to have similar extraction reproducibility (low coefficient of variation < 30%) and Protocol D enabled an acceptable recovery of serum metabolites. The two-step extraction Protocol D (CH2CL2-MeOH followed by MeOH-H2O) resulted in the greatest improvement in metabolite coverage, satisfactory extraction reproducibility, acceptable recovery and environmental safety. The selected protocol was applied to an obesity metabolomics study to obtain different metabolites between participants with obesity and the controls, and to investigate complex metabolic alterations in obesity during a 2-h oral glucose-tolerance test. Our results suggested that this protocol was useful for analyzing serum metabolome changes in obese individuals in the fasting and postprandial state.
Fluorescent/SERS dual-sensing and imaging of intracellular Zn 2+ Anal. Chim. Acta (IF 5.123) Pub Date : 2018-07-17 Dan Li, Yadan Ma, Huazhen Duan, Fei Jiang, Wei Deng, Xingang Ren
A fluorescent and surface-enhanced Raman spectroscopy (SERS) dual-mode probe is developed for imaging of intracellular Zn2+ based on N-(2-(bis(pyridine-2-ylmethyl)amino)ethyl)-2-mercaptoacetamide (MDPA) modified gold nanoparticles (MDPA-GNPs). Benefiting from the chelation-enhanced fluorescence (CHEF) between MDPA-GNPs and Zn2+, the fluorescent intensities of MDPA-GNPs are substantially enhanced with the increment of Zn2+ concentrations, which can be clearly observed by the naked eye. Under physiological conditions, the probe exhibits a stable response for Zn2+ from 1 μM to 120 μM, with a detection limit of 0.32 μM in aqueous solutions. The resultant MDPA-GNPs can be used for ultrasensitive SERS detection of Zn2+ because of the strong inter-particle plasmonic coupling generated in the process of Zn2+-triggered MDPA-GNPs self-aggregation, with a low detection limit of 0.28 pM, which is eight order of magnitude lower than the United States Environmental Protection Agency (US EPA)-defined limit (76 μM) in drinkable water. More importantly, the proposed probe can be applied for efficient detection of intracellular Zn2+ with excellent biocompatibility and cellular imaging capability. Therefore, a highly sensitive and selective nanosensor has been demonstrated for both reliable quantitative detection of Zn2+ in aqueous solution and real-time imaging of intracellular Zn2+, suggesting its significant potential utility in bioanalysis and biomedical detection in the future.
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