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  • Electrochemical Determination of Sesamol in Foods by Square Wave Voltammetry at a Boron-Doped Diamond Electrode
    Anal. Lett. (IF 1.248) Pub Date : 2019-08-06
    Burak Aslışen; Çağrı C. Koçak; Süleyman Koçak

    Sesamol is a phenolic compound naturally found in sesame seeds. It has beneficial health effects in humans, as it features significant antioxidant activity and has anticancer and anti-aging properties. Therefore, finding a suitable electrode surface for sesamol determination is important. The prominent advantage of boron-doped diamond electrodes is their use in many sensing platforms without the need for the surface modification. This study represents the first time that sesamol has been determined using boron-doped diamond electrodes in acidic media by square wave voltammetry. Linear responses of sesamol were obtained in the concentration range from 0.2 µM to 1000 µM, and the detection limit was determined to be 85 nM based on a signal-to-noise ratio of 3. The relative standard deviations were 2.1% for a 1 µM standard with three measurements.

    更新日期:2020-01-02
  • Simultaneous Determination of Prochloraz and Three Metabolites in Fruits and Vegetables by Liquid Chromatography – Tandem Mass Spectrometry (LC-MS/MS)
    Anal. Lett. (IF 1.248) Pub Date : 2019-08-14
    Yan Fu; Quansheng Wang; Liang Zhang; Yinliang Wu

    An analytical method was established to simultaneously determine prochloraz and three metabolites N-propyl-N-[2-(2,4,6-trichlorophenoxy)ethyl] urea(BTS44595), N-formyl-N-propyl-N-[2-(2,4,6-trichlorophenoxy)ethyl] urea(BTS44596), and 2,4,6-trichlorophenol(BTS45186) in fruits and vegetables. The analysis was performed by liquid chromatography – tandem mass spectrometry (LC-MS/MS) in the positive and negative ion-switching multiple reaction modes (MRM). The analytes were extracted using acetonitrile. The extract was further purified by dispersive solid phase extraction. The linearity of the matrix-matched calibration curves was verified with correlation coefficients (r) greater than 0.9975. Recoveries in fruits and vegetables were conducted at four appropriate concentrations. The average recoveries of the method ranged from 80% to 105%, and the relative standard deviations were less than 15%. The limits of detection and quantification of the analytes in fruits and vegetables were from 0.1 to 1 µg/kg and 0.5 to 5 µg/kg, respectively. The method was validated and demonstrated to be suitable for the determination of prochloraz and three metabolites in fruits and vegetables.

    更新日期:2020-01-02
  • Simultaneous Determination of Multiple Biomarkers for Breast Cancer Based on a Dual-Tagged Fluorescent Probe
    Anal. Lett. (IF 1.248) Pub Date : 2019-08-13
    Manman Zhang; Xin Li; Ge Gao; Chunyan Deng

    A simple fluorescent biosensor was developed for the simultaneous determination of the breast cancer-related biomarkers human epidermal growth factor receptor 2 (HER2) and microRNA-21. Black Hole Quencher 2 (BHQ2) labeled DNA1, carboxyl fluorescein (FAM)-modified human epidermal growth factor receptor 2 (HER2) aptamers, and sulfo-cyanine5 carboxylic acid (Cy5)-modified DNA2 were involved. The fluorescent probe was prepared by a one-step procedure. In this sensing system, FAM and Cy5 were close to BHQ2, and therefore, the fluorescent intensity of this proposed probe was weak. However, in the presence of HER2 and microRNA-21, the fluorescent signals were enhanced with increasing concentrations. The detection of HER2 and microRNA-21 was achieved in a simple process. The detection limits for HER2 and microRNA-21 were 0.042 ng mL−1 and 0.048 pM, respectively. In summary, this analytical approach is simple, rapid, cost-effective, low cost, selective, and accurate which are important characteristics in clinical analysis. Therefore, we anticipate that this fluorescent biosensing protocol may have practical applications in clinical measurements to provide early disease diagnosis and monitoring.

    更新日期:2020-01-02
  • Structural and property changes of silk fibroin determined by an immunoassay during an artificial aging process
    Anal. Lett. (IF 1.248) Pub Date : 2019-08-14
    Jin Li; Yujie He; Haohui Li; Yi Ouyang; Linshuai Liu; Yang Zhou; Zhiwen Hu; Bing Wang

    Recently, increasing interest has been focused on the origin and transmission of silk. However, ancient silks have usually undergone severely deterioration and investigations of the sequential and spatial structural changes in the degradation process have rarely been reported. In this paper, a novel immunoassay was proposed for investigating the structural changes of silk fibroin (SF) at sequential level during an alkali aging process. Three polyclonal and one monoclonal antibodies, i.e., HAPJ0449, HAPH1223, HAPJ0409, and HAMK0111, were accurately prepared through animal immunization. Next, a sensitive indirect enzyme-linked immunosorbent assay (ELISA) based on the antibodies was performed to characterize the aged silks. The ELISA results indicated that the macromolecular structure of silk fibroin degraded gradually with an increase in the alkali aging time interval. The antibodies produced by immunizing rabbits with hapten-keyhole limpet hemocyanin (KLH) conjugate exhibit superior sensitivity to those obtained by immunization with silk fibroin. Moreover, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and attenuated total reflectance—Fourier transform-infrared spectroscopy (ATR-FTIR) results showed the molecular weight and crystallinity index of silk samples decreased during the aging process. Thus, combined with conventional analytical tools, the immunological method has the potential to provide an accurate and reliable quantitative index for aging assessment of severely degraded silks, which may serve as a reference for studying the origin and transmission of these materials.

    更新日期:2020-01-02
  • Exploring Chemical Profiles and Bioactivities of Harungana madagascariensis Lam. ex Poir. Leaves and Stem Bark Extracts: A New Source of Procyanidins
    Anal. Lett. (IF 1.248) Pub Date : 2019-08-19
    Eulogio J. Llorent-Martinez; Alba Ruiz-Riaguas; Kouadio Ibrahime Sinan; Kouadio Bene; Maria Luisa Fernández-de Cordova; Carene Picot-Allain; Fawzi Mahomoodally; Hammad Saleem; Gokhan Zengin

    This study attempts to valorize the multiple pharmacological properties of Harungana madagascariensis Lam. ex Poir., also known as dragon’s blood tree, with wide applications in African traditional medicine. The antioxidant and inhibitory activity of H. madagascariensis leaves and stem bark extracts (ethyl acetate, aqueous extracts, and methanol) against enzymes related to diabetes (α-glucosidase, α-amylase), epidermal hyperpigmentation problems (tyrosinase), and Alzheimer’s disease (acetyl and butyryl cholinesterase) were evaluated. The phytochemical profiles of the extracts were studied by high-performance liquid chromatography with diode array detection and mass spectrometry (HPLC-DAD-MS), observing the presence of procyanidins and flavonoids, particularly in the leaves’ extracts. The radical scavenging and reducing power of H. madagascariensis leaves’ extracts were greater than the stem bark extracts. The methanol extracts of leaves (4.61 mg galantamine equivalent (GALAE)/g extract) and stem bark (4.68 mg galantamine (GALAE)/g extract) of H. madagascariensis inhibited acetyl cholinesterase. Methanol extracts (153.55 and 147.07 mg kojic acid equivalent (KAE)/g extract, for leaves and stem bark extracts, respectively) of H. madagascariensis showed high tyrosinase inhibition. Correlation and principal component analysis (PCA) were also performed. The observed pharmacological effects of H. madagascariensis support that this plant may be a promising candidate for the development of novel pharmacophores for the treatment of diabetes, epidermal hyperpigmentation problems, Alzheimer’s disease, and other oxidative-stress-related complications.

    更新日期:2020-01-02
  • Simultaneous Analysis for the Multiple Periodontal Pathogens by High-Speed Capillary Electrophoresis
    Anal. Lett. (IF 1.248) Pub Date : 2019-08-20
    Jin Chen; Fengchao Wang; Yi Ni; Xiaoming Dou

    In the present study, one important branch of high-speed capillary electrophoresis (HSCE), short-end CE, was employed for the highly efficient analysis of Porphyromonas gingivalis (Pg), Treponema denticola (Td), and Tannerella forsythia (Tf), which are closely related to the occurrence of periodontal disease. Aiming to realize rapid and simultaneous detection, a 100 bp DNA ladder marker ranging from 100 to 1500 bp was employed as the standard for the optimization of polymer concentration and electric field strength in developed protocol. The results showed that the PCR (polymerase chain reaction) products of Pg (197 bp), Td (311 bp), and Tf (641 bp) were simultaneously identified and quantitated in approximately 90 s using electrophoretic conditions that included 0.4% hydroxyethylcellulose (HEC, 1300 K) and a 200 V/cm electric field with an effective length of separation equal to 2.5 cm. The detected concentrations of the above target samples, determined by a time-modified internal standard route, were 1.08, 1.60, and 2.46 ng/µl, respectively. The present short-end CE strategy featured favorable properties for reproducibility, accuracy and linearity, whose evaluation included the values of relative standard deviation and the correlation coefficient. The current work may provide an effective avenue for the clinical detection of periodontal disease.

    更新日期:2020-01-02
  • Contactless Resonant Cavity Dielectric Spectroscopic Studies of Cellulosic Paper Aging
    Anal. Lett. (IF 1.248) Pub Date : 2019-08-28
    Mary Kombolias; Jan Obrzut; Michael T. Postek; Dianne L. Poster; Yaw S. Obeng

    The current analytical techniques for characterizing printing and graphic arts substrates, particularly those used to date and authenticate provenance, are destructive. This limits the amount of data that can be captured from an individual sample. For samples being evaluated in forensic and archeological investigations, any loss or degradation of the materials is undesirable. Furthermore, it is difficult to produce statistically relevant data for such analytes. We have shown elsewhere that a contactless microwave resonant cavity dielectric spectroscopy technique can discriminate between paper samples made from different plant fiber species based on their lignin content. In this publication, we demonstrate the utility of the contactless resonant cavity dielectric spectroscopy (RCDS) technique in the characterization of naturally and artificially aged paper samples. Based on our experimental results, we suggest that the technique could be used in forensic and archeological investigations of unique paper products.

    更新日期:2020-01-02
  • Evaluation of sample preparation methods for the determination of Cd, Cr and Pb in ceramic tableware by graphite furnace atomic absorption spectrometry
    Anal. Lett. (IF 1.248) Pub Date : 2019-08-21
    Eliézer Quadro Oreste; Alexander Ossanes de Souza; Camila Corrêa Pereira; Daisa Hakbart Bonemann; Mariana Antunes Vieira; Anderson Schwingel Ribeiro

    This work presents a study involving the determination of Cd, Cr and Pb in ceramic tableware by graphite furnace atomic absorption spectrometry (GF AAS) using a simple and practical slurry sampling method. A central composite design (CCD) was used to optimize the slurry sampling conditions. The obtained results were confronted by the ultrasonic acid decomposition, evaluating the instrumental parameters relevant to the accuracy and precision. In addition, recovery measurements of the analytes were performed and ranged between 90% and 111% for both methods. The concentrations obtained were in the range from 0.04 to 184; 67 to 1395 and 42 to 5305 μg g−1 for Cd, Cr and Pb, respectively. These concentrations were higher for some ceramic samples, which may be related to the raw material used for their manufacture and also due to the pigment used during the decoration process. In addition, the leaching study observed concentrations in the range from 0.07 to 1.68; 0.1 to 5.0 and 0.6 to 46.3 μg g-1 for Cd, Cr and Pb, respectively, and there is a possibility of migration of these toxic metals from the ceramic materials to the food.

    更新日期:2020-01-02
  • Preconcentration of Sulfamethoxazole Using a Molecularly Imprinted Polymer (MIP) Prepared by Zeolitic Imidazolate Framework-8 - Hemoglobin Catalyzed by Electrochemically Mediated Atom Transfer Radical Polymerization with Electrochemical Determination on a Screen-Printed Electrode
    Anal. Lett. (IF 1.248) Pub Date : 2019-10-22
    Xiaoya Zhao; Peng Wang; Cheng Ye; Han Wang; Wei Cao

    A novel approach was developed to prepare molecularly imprinted polymer (MIP) composites on filter paper and with the subsequent determination of sulfamethoxazole in food samples. Hemoglobin was firstly encapsulated in a metal-organic framework to improve its stability and catalytic performance. This mixture was modified with an initiator and immobilized in the paper to prepare the MIP using electrochemically mediated atom transfer radical polymerization. This composite exhibited excellent adsorption capacity (60.1 mg g−1) and rapid kinetics, which were better than those of previously reported MIPs. Using the optimized conditions, this MIP composite directly extracted the sulfamethoxazole from complex food samples and was placed on the surface of a screen-printed electrode to quantify sulfamethoxazole with a detection limit of 0.7 ng mL−1. Sulfamethoxazole recoveries ranged from 99.4 to 103.7% and the results were in good agreement with those obtained by a liquid chromatography – mass spectrometry (LC-MS) method (r = 0.992). This approach may also be applied for the determination of other target molecules.

    更新日期:2020-01-02
  • Simultaneous Determination of 35 Organic Metabolites Including Amino Acids, Creatine, Creatinine, and Oxidized and Reduced Glutathione in Lung Tissue, Plasma and Urine Using Liquid Chromatography–Tandem Mass Spectrometry
    Anal. Lett. (IF 1.248) Pub Date : 2019-08-30
    Chan Seo; Sung Hwan Kim; Hyeon-Seong Lee; Hyung-Jin Park; Youngbae Kim; Moongi Ji; Jeuk Min; Shong-Jin Oh; Kyuhong Lee; Man-Jeong Paik

    A simple and rapid method for the simultaneous determination of 35 non-derivatized metabolites was developed using liquid chromatography – tandem mass spectrometry. Under the optimal conditions, linearity was achieved in the range from 0.05 to 10.0 ng (R2 ≥ 0.989). The repeatability provided percentage relative standard deviations ≤11.2 and a trueness expressed as percentage relative error from −10.7% to 12%. The recoveries ranged from 87.3% to 109.8% with good repeatability. When applied to mouse lung tissue, plasma, and urine samples, 30 amino acids, creatine, creatinine, and oxidized glutathione were positively identified and quantified. The described present method was useful for the simultaneous determination of amino acids, creatine, creatinine, and oxidized glutathione in biological samples, including tissue, plasma, and urine.

    更新日期:2020-01-02
  • Prompt Screening of the Alterations in Biochemical and Mineral Profile of Wheat Plants Treated with Chromium Using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy and X-ray Fluorescence Excited by Synchrotron Radiation
    Anal. Lett. (IF 1.248) Pub Date : 2019-08-25
    Sweta Sharma; A. K. Singh; M. K. Tiwari; K. N. Uttam

    With mounting pressure of heavy metal pollution on agriculture, the demand of practical tools and protocols for nondestructive, pre-visual detection of plant response towards heavy metals has received great impetus. Advances in modern spectroscopic techniques such as synchrotron radiation X-ray fluorescence and attenuated total reflectance Fourier transform infrared spectroscopy have the capability of providing a complete picture of the metabolic events taking place in plants stressed with heavy metals without subjecting the sample to pre-processing. The present study explores the utility of synchrotron radiation X-ray fluorescence and attenuated total reflectance Fourier transform infrared spectroscopy along with multivariate analysis for the detection of the response as spectral indices of wheat seedlings towards chromium treatment. For this, wheat has been grown under optimized growth conditions and exposed to chromium at concentrations from 20 to 100 µM. The synchrotron radiation X-ray fluorescence spectra of control and chromium exposed seedlings show that exposure to chromium leads to its accumulation in the leaves of wheat seedlings which results in a reduction of the uptake of calcium, potassium, manganese iron, copper and zinc by the seedlings. The alterations in the biochemicals of wheat seedlings as a result of chromium exposure have been assessed by attenuated total reflectance Fourier transform infrared spectroscopy. Analysis of the infrared data reveals that chromium significantly alters the spectral signatures of cellulose, pectin, hemicelluloses, lignin, amide II, amide I and lipid in the leaves of wheat seedlings. The observed changes are dependent on the dose of chromium. The spectral signatures obtained in this study serve as important monitoring indices for observing alterations in the physiological, biochemical and metabolic status of plants under heavy metal stress.

    更新日期:2020-01-02
  • Accurate and Precise Determination of Gold in Plating Bath Solution: Deep Eutectic Solvent Based Liquid Phase Microextraction – Slotted Quartz Tube – Flame Atomic Absorption Spectrometry
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-17
    Özge Yılmaz, Büşra Yılmaz Durak, Zeynep Tekin, Elif Seda Koçoğlu, Sezgin Bakırdere

    A sensitive, simple and green deep eutectic solvent based liquid phase microextraction (DES-LPME) method is described for the quantification of trace gold by flame atomic absorption spectrometry with a slotted quartz tube (SQT-FAAS). A 1:2 choline chloride:phenol mixture was utilized as the DES for the extraction of gold from the aqueous solution. All of the parameters affecting the extraction efficiency were optimized to increase the detection power of the FAAS. Under the optimum conditions, the presented method provided a linear range between 15 and 400 µg/L with limits of detection and quantification of 5.1 and 16.9 µg/L, respectively. An approximate 58-fold improvement was obtained in the detection power of the FAAS based on the limit of detection using the optimized DES-LPME-SQT-FAAS method. In order to check the validity/applicability of the method, recovery measurements were performed for spiked gold plating bath samples and the resulting recoveries were between 105.3% and 107.6%. The presented method was employed for real sample analysis.

    更新日期:2019-12-02
  • Immunoassay for Highly Water-Soluble Nitenpyram: Evaluating the Analytical Performance of an Easy-to-Use Screening Method for Agricultural Samples
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-19
    Eiki Watanabe, Yuki Hirakawa, Tomomi Yamasaki, Seiji Iwasa, Shiro Miyake

    Nitenpyram, a neonicotinoid insecticide, is highly soluble in water (>5.9 × 105 mg/L). Specifically examining its physicochemical properties, we have established a simple and rapid residue analytical method for nitenpyram using an enzyme-linked immunosorbent assay (ELISA) which requires no organic solvents. The I50 value found with this ELISA method using a selective monoclonal antibody toward nitenpyram was 4.8 ng/mL. A hand-shaking method using water was applied for ELISA analysis to extract nitenpyram from fruiting vegetable samples of four kinds. Matrix effects caused by interfering substances coexisting in aqueous sample extracts were reduced by dilution with water. No problems were found in the analytical values obtained using ELISA. From analyses of nitenpyram-incurred fruiting vegetables with the proposed ELISA and the reference HPLC protocols, high mutual correlation was found, which suggests that the measurement accuracy of the proposed ELISA method is comparable to the reference HPLC procedure.

    更新日期:2019-12-02
  • Air Assisted Dispersive Liquid–Liquid Microextraction (AA-DLLME) Using Hydrophilic–Hydrophobic Deep Eutectic Solvents for the Isolation of Monosaccharides and Amino Acids from Kelp
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-22
    Guizhen Li, Kyung Ho Row

    Air assisted dispersive liquid–liquid microextraction (AA-DLLME) using hydrophilic–hydrophobic deep eutectic solvents (DES) was developed for the simultaneous isolation of monosaccharides and amino acids with wide ranges of polarities from kelp using high performance liquid chromatography (HPLC). A response surface methodology (RSM) on a Box–Behnken design (BBD) model was employed to identify the optimal extraction parameters. Air assisted dispersive liquid-phase microextraction performed using the optimum deep eutectic solvent system, five push–pull cycles, a ratio of solid to liquid equal to 3 mg·mL−1, 10% (w/v) NaCl, and a centrifugation time of 6 min provided the best analytical performance. The optimal extracted concentrations of d-(+)-galactose, l-(-)-fucose, dl-tyrosine, and dl-valine in kelp were 16.7 ± 0.2, 8.6 ± 0.2, 2.6 ± 0.1, and 1.6 ± 0.1 mg·g−1, respectively. The method recoveries for d-(+)-galactose, l-(-)-fucose, dl-tyrosine, and dl-tyrosine were from 87 to 102%, 84 to 103%, 87 to 104%, and 85 to 103%. The relative standard deviations (RSDs) (n = 4) for the intra-day and inter-day determinations were <6.17%.

    更新日期:2019-12-02
  • Classification of Nephrite Using Calibration-Free Laser Induced Breakdown Spectroscopy (CF–LIBS) with Comparison to Laser Ablation–Time-of-Flight–Mass Spectrometry (LA–TOF–MS)
    Anal. Lett. (IF 1.248) Pub Date : 2019-08-22
    Zeshan Adeel Umar, Usman Liaqat, Rizwan Ahmed, Muhammad Aslam Baig

    Laser induced breakdown spectroscopy (LIBS) and laser ablation–time-of-flight–mass spectrometry (LA–TOF–MS) have been employed for the identification and classification of nephrite jade from the Mohmand district of Khyber Pakhtunkhwa (KP), Pakistan. The optical emission spectrum of the laser produced nephrite jade plasma shows the spectral lines of Ca, Mg, Fe and Si as major elements along with traces of Na. Calibration-free laser induced breakdown spectroscopy (CF–LIBS) has been used for the compositional analysis of the sample. The mass spectrum of nephrite jade acquired using LA–TOF–MS confirms the presence of the same major and trace elements identified by LIBS. The Mg/(Mg + Fe) ratios calculated using both the techniques of 0.27 ± 0.08 by CF–LIBS and 0.22 ± 0.05 by LA–TOF–MS confirm that the nephrite jade from the Mohmand district of Khyber Pakhtunkhwa is of the ferro-actinolite type.

    更新日期:2019-12-02
  • Characterization of Paraffin-Waxed Apples by Raman Spectroscopy
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-22
    Xiaofan Du, Sijia Wang, Ping Wang, Qing Gu, Jing Xin, Zhenxi Zhang, Jing Wang, Cuiping Yao

    Inexpensive industrial paraffin wax is often coated on the surface of apples to keep them fresh; however, this material is toxic and harmful to human health. Currently, convenient and effective methods to detect paraffin wax residues on the surface of apples are unavailable. Here a Raman spectroscopy-based technique is reported to identify industrial paraffin-waxed apples, and a quantitative detection model was established. An 8 × 8 point scan with an area of 0.16 mm2 was conducted to construct a three-dimensional map of the concentration distribution of industrial paraffin wax on the surface of waxed apples before and after washing, as well as for apple flesh 1 mm below the peel. Results demonstrated that the industrial paraffin wax did not penetrate into the flesh and that peeling the apples provides an effective means to eliminate the toxic industrial paraffin wax. This study provides a practical approach to identify fruits coated with industrial paraffin wax.

    更新日期:2019-12-02
  • Differential Pulse Voltammetric (DPV) Determination of the Local Anesthetic Bupivacaine using Polyimide Membrane-Based Electrodes
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-26
    Öznur Güngör, İmren Özcan, Mehmet Ali Erdoğan, Burhan Ateş, Süleyman Köytepe

    Aromatic selective polyimide (PI) membrane based voltammetric electrodes were prepared for bupivacaine measurements. Polyimide membranes were synthesized from 4,4′-diaminobenzanilide (DABA) and different aromatic dianhydrides (pyromellitic dianhydride (PMDA), benzophenone-3,3′,4,4′-tetracarboxylic dianhydride (BPDA), 4,4′-oxydiphthalic anhydride (ODPA)) through two-step polycondenzation reactions. The structural properties of the obtained benzanilide based PIs were characterized by various analytical techniques. For the preparation of voltammetric electrodes, these polyimide films were coated with polyimide solution by drop-casting on the surface of a platinum working electrode. Due to the excellent film properties and suitable porosity, the prepared benzanilide based polyimide films were used as the membrane for selective determination of bupivacaine in the presence of interferents that included lactose, glucose and sucrose. For this reason, the selectivity of the modified electrode to bupivacaine obtained from the prepared PI film toward the potential interferences was investigated by differential pulse voltammetry (DPV). The results of voltammetric study showed that polyimide films responded to only bupivacaine at a potential of approximately +0.92 V. The polyimide membrane modified electrode showed a rapid response time, a high R-value of 0.9941, high reproducibility and good selectivity for bupivacaine. The limit of detection (LOD) and the limit of quantitation (LOQ) were determined to be 16.82 µM and 50.46 µM, respectively. Thus, benzanilide based polyimides may be successfully used as selective membranes for preparation of bupivacaine sensors. This structure may be a precursor for the preparation of simultaneous or needle-shaped sensors in the future.

    更新日期:2019-12-02
  • Human Enamel and Dentin: Effect of Gender, Geographic Location and Smoking Upon Metal Concentrations
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-30
    Almir Olovčić, Emina Ramić, Mustafa Memić

    The goal of this study was to determine the content of 12 metals in 23 samples of teeth from two cities in Bosnia and Herzegovina (B&H): Sarajevo, a capital city with heavy traffic, industrial facilities, and long periods of smog during winter and Bihac, a picturesque small city, with no industrialization, settled among vivid national park and rivers. The teeth were separated into enamel and dentin. Dissolution of samples was performed in concentrated HNO3 with the addition of H2O2 followed by flame atomic absorption spectroscopy (FAAS) analysis. The results showed expected high contents of Ca, Na, Mg, and K, while elevated contents of Cu, Fe, and Zn were present in some samples. K and Na showed uniform distributions throughout enamel and dentin. Alkaline and earth-alkaline metals showed significant positive correlations. Zinc and manganese exhibited differences in the dentin content based on the place of residence. Zinc also displayed statistically significant differences between smokers’ and nonsmokers’ dentin samples. The differences were more pronounced between intra groups (within one sample) than for inter groups (within different groups, such as location, gender, and smoking).

    更新日期:2019-12-02
  • Preconcentration and Determination of Chlorophenols in Wastewater with Dispersive Liquid–Liquid Microextraction Using Hydrophobic Deep Eutectic Solvents
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-27
    Yena An, Wanwan Ma, Kyung Ho Row

    Hydrophobic deep eutectic solvents (DESs) were synthesized and developed for the preconcentration of three chlorophenols from wastewater by dispersive liquid–liquid microextraction (DLLME). The analyte concentrations were determined by high-performance liquid chromatography (HPLC). The hydrophobic DESs were prepared with the combination of hydrogen bond donors of decanoic acid or octanoic acid with different hydrogen bond acceptors of quaternary ammonium salts of tetrabutylammonium chloride, tetraoctylammonium chloride, methyltrioctylammonium chloride, and tetraheptylammonium chloride). Following the study of the stability and characterization by Fourier transform infrared spectroscopy, the hydrophobic DESs were developed as extractants and employed for the removal of 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) from wastewater. Using hydrophobic DESs as the microextraction solvents, several key parameters were optimized, including the type and volume of the hydrophobic DES, pH, and time of the extraction procedure. Under the optimized conditions, good recoveries from 90.8% to 93.0% were obtained for the three chlorophenols. The limits of detection were less than 0.05 µg/mL with relative standard deviations between 1.8% and 3.1%. The method was applied for the isolation and determination of synthetic chlorophenols in wastewater.

    更新日期:2019-12-02
  • Improved Method for the Determination of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans (PCDD/Fs) in Sanitary Napkins
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-30
    Young Sang Kwon, Sung-Gil Choi, Seung-Min Lee, Jong-Hwan Kim, Sang Gon Kim, Dong Yeol Lee, Jong-Su Seo

    An improved method was developed for determining highly toxic 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo-p-furans (PCDD/Fs) in sanitary napkins. Samples were extracted by Soxhlet (50% dichloromethane/hexane) and sonication (hexane), and a multi-layer silica column was used for clean-up after acetone precipitation to separate the superabsorbent polymers. Improved separation efficiency of PCDD/Fs from sanitary napkins with a high level of superabsorbent polymers was achieved using the acetone precipitation method. Hexane was then applied as an alternative solvent to remove residual interfering substances including sticky components contained on sanitary napkins via alumina column chromatography in the second clean-up step. Recoveries approached 100% with an average relative standard deviation of less than 15%, and recoveries of internal standards were from 70.5 to 114.8% and 0.6 to 13.6% for the two extraction methods. The mean method detection limit was 0.075–0.968 pg/g for Soxhlet extraction and 0.0032–0.091 pg/g for sonication extraction. The established method meets the quality criteria for the screening of dioxins stated in EU Regulations 589/2014 and 709/2014, and therefore provides a suitable alternative for the determination of dioxins in sanitary napkins containing superabsorbent polymers.

    更新日期:2019-12-02
  • Real-Time Distinguishing of the Xylene Isomers Using Photoionization and Dissociation Mass Spectra Obtained by Femtosecond Laser Mass Spectrometry (FLMS)
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-27
    Abdullah Kepceoğlu, Yasemin Gündoğdu, Kenneth William David Ledingham, Hamdi Sukur Kilic

    Distinguishing chemicals and improvement on analytical methods has a direct impact on modern chemical analysis. In this work, the dissociative ionization of xylene isomers was investigated using a femtosecond laser mass spectrometry (FLMS) method with a custom-built linear time-of-flight (TOF) instrument. Laser beams at 800 nm and 400 nm were used and intensity-dependent analysis of the obtained mass spectra was performed using principal component analysis (PCA) to distinguish the xylene isomers, which give identical mass spectra in appearance that cannot be distinguished using normal mass spectrometry methods. The results show that there is a statistically highly significant difference between the xylene isomers for two principal components (1 − α > 99.99%) and minimal information loss (<5%) took place during the PCA procedure. Also, the use of the k-medoid clustering method showed that the isomers may be distinguished in real-time for a wide range of ionization laser pulse powers with approximately 99% accuracy. The results suggest that real-time isomer analysis by the FLMS method is suitable for mass spectral identification applications. The FLMS method has been shown to be an important alternative to other mass spectrometric methods that use different ionization mechanisms.

    更新日期:2019-12-02
  • Electrochemical Determination of Tyrosine using a Novel Tyrosinase Multi-Walled Carbon Nanotube (MWCNT) Polysulfone Modified Glassy Carbon Electrode (GCE)
    Anal. Lett. (IF 1.248) Pub Date : 2019-08-06
    Lisebo Phelane, Carla Gouveia-Caridade, Madalina M. Barsan, Priscilla G. L. Baker, Christopher M. A. Brett, Emmanuel I. Iwuoha

    The modification of polysulfone (PSF) with multi-walled carbon nanotubes (MWCNT) is presented as a platform for the development of a tyrosinase biosensor. PSF, dissolved in dichloromethane, was deposited on a glassy carbon electrode (GCE), after which MWCNT functionalized in nitric acid, was drop coated on the PSF layer. Tyrosinase enzyme (TyOx), crosslinked with glutaraldehyde, was subsequently deposited on the MWCNT/PSF/GCE transducer to constitute the tyrosinase biosensor. The MWCNT/PSF/GCE (sensor) and TyOx/MWCNT/PSF/GCE (biosensor) were characterized using cyclic voltammetry and electrochemical impedance spectroscopy. Scanning electron microscopy was used to study the morphological changes after each modification step. Cyclic voltammetry measurements confirmed that MWCNT/PSF/GCE was a better platform for the direct detection of tyrosine than MWCNT/GCE or PSF/GCE. A well-defined analytical peak at 0.79 V with respect to Ag/AgCl was observed that was clearly distinguishable from the background current. The tyrosinase biosensor showed a very low limit of detection (0.3 nM) and a very high sensitivity (1.988 µA µM−1 cm−2) towards tyrosine detection compared to comparable devices reported in the literature.

    更新日期:2019-12-02
  • Comparison of Methods for the Preconcentration of Cadmium (II) Using Amberlite XAD-16 Resin Modified with Anoxybacillus caldiproteolyticus and Geobacillus stearothermophilus as Novel Biosorbents
    Anal. Lett. (IF 1.248) Pub Date : 2019-08-13
    Barış Enez, Elif Varhan Oral, Sema Aguloglu Fincan, Berrin Ziyadanogullari

    The isolation, identification and characterization of bacteria obtained from soil of Ergani Makam Mountain were performed and the results revealed that the bacteria were thermophilic Anoxybacillus caldiproteolyticus. The characterized bacteria and purchased Geobacillus stearothermophilus were immobilized on Amberlite XAD-16 in order to prepare two biosorbents for preconcentration experiments for the determination of cadmium (II) ions. The produced biosorbents were enriched separately using mini-columns and the analyte was determined by flame atomic absorption spectrometry. The effects of solution parameters were investigated for the separation and preconcentration yields. The recovery efficiencies of Amberlite XAD-16 immobilized separately with A. caldiproteolyticus and G. stearothermophilus were determined to be 98.23 ± 2.40 and 98.93 ± 1.3 (n = 5) for the optimum working conditions, respectively. Moreover, the Cd (II) ion was recovered with 10 mL of 1 mol L−1 of HCl and 2 mL of 0.5 mol L−1 HNO3 solutions. The optimum working conditions were determined to be at pH 6.0 and a flow rate of 2 mL min−1 for both biosorbents. The recovery efficiencies of matrix ions were characterized to investigate the feasibility of the developed preconcentration methods. The accuracy of the proposed methods were controlled by analyzing a SCP Science EnviroMAT Waste Water, Low (EU-L-2) certified reference material. The obtained results were comparable to the certified values. These methods were also applied to the analysis of water samples from Dicle River, Hazar Lake and Diyarbakır tap water for Cd (II).

    更新日期:2019-12-02
  • Polyamic acid (PAA) immobilized on glassy carbon electrode (GCE) as an electrochemical platform for the sensing of tuberculosis (TB) antibodies and hydrogen peroxide determination
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-05
    Xolani Terrance Ngema, Priscilla Baker, Fanelwa Ajayi, Pierre-Henri Aubert, Philippe Banet

    Tuberculosis (TB) is a chronic infectious disease that usually affects the pulmonary region of human beings. It remains critically important to develop cost effective methods for TB detection, especially since impoverished communities are often the target population. Immunological assays are commonly used for the detection of TB and are typically based on selected antibody (Ab) antigen (Ag) interactions as measured by the enzyme-linked immunosorbent assay (ELISA). It is also common to have tagged antibody/antigen binding pairs where the signaling is produced by the tag as is the case with the indirect tuberculosis IgG ELISA Kit, where a horseradish peroxidase (HRP) tag on the antibody is responsible for the analytical signal. Mycobacterium tuberculosis (MTB), recombinant protein antigen 85B (Ag85B), is the most abundant protein exposed by Mycobacterium tuberculosis acting as a potent immuno-protective antigen. In this work, both Ag85B and antibody-HRP (Ab-HRP) were immobilized on a semi-conductive polyamic acid (PAA) electrochemical interface towards the design of new electrochemical sensors. In a first approach, the antigen, Ag85B, was employed as the bioreceptor to afford label-free TB signaling through antibody detection and the obtained limit of detection was 8 μg/mL of antibody. The response was evaluated by voltammetric methods and electron impedance spectroscopy (EIS). Cyclic voltammetry (CV) and EIS were used to characterize the charge transfer and capacitive behavior of the label-free sensor. In a second approach, the HRP tagged antibody was used for the design of a stable hydrogen peroxide (H2O2) sensor with very good analytical performance with a limit of detection equal to 1.3 μM. Even though we developed an ultrasensitive H2O2 sensor, no further development of TB antigen detection was possible in this work.

    更新日期:2019-11-11
  • Monolithic Column Ion-Pair Chromatography with Indirect Ultraviolet Detection for the Determination of Three Acid Radical Anions Containing Fluorine in Ionic Liquids
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-05
    Sheng Liu, Xinxin Jin, Yajie Ma, Hongxing Li, Hong Yu

    A rapid ion-pair chromatographic method was developed on a monolithic column for the determination of trifluoroacetate, trifluoromethanesulfonate, and tetrafluoroborate. The three anions were successfully detected using indirect ultraviolet detection. These analyte anions were separated using a tetrabutylammonium hydroxide - p-toluenesulfonic acid – acetonitrile mobile phase on a silica-based monolithic column with an octadecyl functional group. The effects of detection wavelength, mobile phase, column temperature and flow rate on the retention of the anions were investigated. The chromatographic conditions were optimized and the retention properties were evaluated. Under the selected optimal conditions, the successful separation of the anions was achieved within 3.5 min. The detection limits were less than 1.0 mg/L for trifluoroacetate, trifluoromethanesulfonate, and tetrafluoroborate. The relative standard deviations for five repeated measurement of retention time and peak area were no more than 0.2%. The linear ranges extended across two orders of magnitude. The three anions in synthetic ionic liquid samples were successfully separated and detected by this method. The results show that the recoveries of this method were between 94.0% and 99.0%. The method was rapid, simple, and easy to use.

    更新日期:2019-11-11
  • Spatially Resolved Characteristics of Solution Cathode Glow Discharge Source Coupled with an Interference Filter Wheel as Spectral Discrimination Device
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-10
    Peichao Zheng, Weiqi Li, Jinmei Wang, Xiang Zhai, Xuefeng Mao, Xiaofa Wang, Chunhong Lai

    Solution cathode glow discharge-atomic emission spectrometry (SCGD-AES) has attracted wide attention globally in recent years. The technology has the advantages of on-line detection of various metal elements, small volume, and convenience. In this work, the original spectrometer based on SCGD-AES technology was replaced by filter-wheel, photomultiplier tube (PMT) and picoammeter, which was named FPP spectral discrimination device. Analytical performance of the device with narrow-band monochromator (0.08 nm) was compared to its performance with wide-bandpass filters (10 nm) with optimized spatial. The relative standard deviation of SCGD-FPP for Na, K, Ca, Li, Sr, Rb, and Cs ranged from 0.2 to 0.8%, comparable to the 0.6 to 1.4% with the monochromator. With optimized spatial resolution, the detection limits ranged from 0.15 to 350 μg/L, and the optimal plasma spectral collected points of Na, K, Ca, Li, Sr, Rb, and Cs at 0.8 mm, 0.8 mm, 0.6 mm, 0.4 mm, 0.2 mm, 0.6 mm, and 0.6 mm, respectively. The deviation analysis of the samples containing Na, K, Ca, and Li were analyzed under optimal conditions. The results show that a SCGD-FPP source with spatial resolution improved the detection performance.

    更新日期:2019-11-11
  • Intramolecular Charge Transfer (ICT) Based Two-photon Fluorescent Probe for Bisulfite with Bioimaging Applications
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-08
    Guangfu Feng, Yuanchun Du

    A two-photon fluorescent probe has been adopted for bisulfite based on an intramolecular charge transfer (ICT) mechanism. The fluorescence intensity of the probe decreased by 837 fold following treatment with HSO3− and the detection limit was 42 nM. This probe showed excellent properties such as high photostability, good two-photon properties, and large Stokes shifts. More importantly, this approach offers a rapid, highly selective, and sensitive method to determine HSO3− in buffer solutions and real samples. Furthermore, the probe was successfully used for two-photon fluorescence visualization of trace SO2 derivatives in biological systems.

    更新日期:2019-11-11
  • Determination of Piperazine in Eggs Using Accelerated Solvent Extraction (ASE) and Solid Phase Extraction (SPE) with High-Performance Liquid Chromatography – Fluorescence Detection (HPLC-FLD) and Pre-Column Derivatization with Dansyl Chloride
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-08
    Xiaona Bu, Maoda Pang, Bo Wang, Yangyang Zhang, Kaizhou Xie, Xia Zhao, Yajuan Wang, Yawen Guo, Chujun Liu, Ran Wang, Genxi Zhang, Tao Zhang, Xuezhong Liu, Guojun Dai, Jinyu Wang

    A high-performance liquid chromatography – fluorescence detection (HPLC-FLD) method was established for the determination of piperazine residues in whole eggs, albumen, and yolk employing pre-column derivatization with dansyl chloride. The egg samples were treated by accelerated solvent extraction (ASE) and the analytes purified by solid phase extraction (SPE). Acetonitrile/ultrapure water was used as the mobile phase for gradient elution. The linear dynamic range was from 6.80 to 200.0 µg/kg for whole eggs, 7.50 to 200.0 µg/kg for albumen, and 6.50 to 200.0 µg/kg for yolk with coefficients of determination (R2) greater than or equal to 0.9992. The average recoveries of piperazine from egg samples were from 72.86 to 89.26% when the concentrations were equal to the limit of quantification, 0.5 times the maximum residue limit, equal to the maximum residue limit, and twice the maximum residue limits. The relative standard deviations were between 1.73 and 4.99%. The limits of detection of piperazine in eggs were from 1.92 to 2.50 µg/kg, and the limits of quantification were between 6.50 and 7.50 µg/kg. The method meets the requirements of the European Union, the Ministry of Agriculture of the People’s Republic of China and the U.S. Food and Drug Administration (FDA) for the determination of veterinary drug residues. The validated HPLC-FLD method was successfully applied to the determination of piperazine residues in 50 eggs purchased from local supermarkets.

    更新日期:2019-11-11
  • Synthesis of Fluorescent Tremella-like Carbon Nanosheets and Their Application for Sensing of 2,4,6-trinitrophenol
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-04
    Pan Guo, Song Zheng, Yong Wang, Qianfen Zhuang, Yongnian Ni

    Fluorescent tremella-like carbon nanosheets (TCNs) were hydrothermally synthesized using citric acid and adenosine as the starting materials. The resulting product had high quantum yield, water-solubility, and photostability. The addition of 2,4,6-trinitrophenol (TNP) induces remarkable fluorescence quenching, and this phenomenon was used to construct a TNP fluorescence sensor. The fluorescence quenching of TCNs by TNP was shown to be likely due to the inner filter effect. The developed sensor has a wide linear range from 0.05 to 50.0 μM with a detection limit of 5 nM. The TCN-based sensor was used for the determination of TNP in lake water with satisfactory recoveries from 98% to 103%.

    更新日期:2019-11-11
  • New Stationary Ionic Liquid Phases with Quinolinium Cations for Capillary Gas Chromatography
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-08
    Mikhail Vadimovich Shashkov, Vladimir Nikolaevich Sidelnikov, Alina Andreevna Bratchikova

    The work provides the study of quinolinium ionic liquids (ILs)—a new class of stationary phases for capillary gas chromatography (GC). Quinolinium ILs were shown to have new attractive properties. They are not only highly polar, but also very selective for aromatic compounds and oxygenates. Depending on the substituents in the quinolinium ring, the studied ILs possess polarity numbers from 64 to 99, so they are polar and strongly polar. By the variation of the substituent and its position, changes in the prevailing types of interactions with analytes are observed. It is worth noting that Abraham’s constants for the quinolinium phases are significantly different from the previously known imidazolium and pyridinium ionic liquids (ILs) that cause significant variations in their selectivity. The most significant differences are observed in the π–π interactions and hydrogen bond acidity parameters. The investigation of background mass spectra for quinolinium ILs showed the most intense signals related to peaks at m/z 69 and 143 belonging to [CF3]+ and quinolinium ring fragments. The most thermostable ILs are N-propyl-6-methylqionoinium and bis(6-methylquinolinium)hexane that are stable up to 300 °C. With regard to the possible use of quinolinium ILs, apart from the separation of polar substances, it is expected that they will find applications in two-dimensional chromatography for the separation of complex mixtures compose of compounds that differ substantially in their properties. The applications of the columns for the determination of aromatic hydrocarbons in gasoline and phenolic compounds in pyrolysis biodiesel are demonstrated.

    更新日期:2019-11-11
  • Effect of Ultrasonic Treatment on Transformations of Arsenic Species in Edible Mushrooms
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-10
    Shuangyang Chen, Benard Muinde Kimatu, Donglu Fang, Xin Chen, Guitang Chen, Qiuhui Hu, Liyan Zhao

    A study on the transformations of six arsenic species (arsenocholine (AsC), arsenobetaine (AsB), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), arsenite (As(III)), and arsenate (As(V))) was carried out in aqueous solution by ultrasonic treatment. The transformations of arsenic species increased with time. As the ultrasonic power or temperature was increased, transformations of arsenic species were at first enhanced and then decreased. AsC, AsB, As(III) were the most unstable at 600 W and 20 °C. DMA and MMA were stable; AsC was partially transformed to AsB, trimethylarsinic oxide (TMAO), and the more toxic tetramethylarsonium ion (TMA+); AsB was partially transformed to TMAO; and As(III) was easily oxidized to As(V). The reduction of As(V) to As(III) was only observed when the temperature was over 60 °C. The ultrasound treatment conditions with relatively stable arsenic species were 150 to 300 W, 40 to 80 °C, and 0 to 10 min. The relatively stable (150 W, 10 min, 80 °C) and unstable (600 W, 60 min, 20 °C) ultrasonic condition were applied to mushrooms and the transformations of AsC, AsB, and As(III) were observed. Currently, ultrasound-assisted extraction methods have only focused on the extraction efficiency of arsenic species and ignored their transformations. This study may serve as a guide for improving extraction efficiency without minimal transformation of the arsenic forms to reflect the actual contents in edible mushrooms. The study also provides a theoretical basis for making an accurate risk evaluation of human exposure by taking account of possible arsenic transformations during processing prior to consumption.

    更新日期:2019-11-11
  • Application of Phytochemical and Elemental Profiling, Chemometric Multivariate Analyses, and Biological Activities for Characterization and Discrimination of Fruits of Four Garcinia Species
    Anal. Lett. (IF 1.248) Pub Date : 2019-08-30
    Nargis Jamila, Naeem Khan, In Min Hwang, Eun Yeong Nho, Ji Yeon Choi, Amir Atlas, Sadiq Noor Khan, Farhat Amin, Fatima Javed, Kyong Su Kim

    Species of Garcinia (Guttiferae) are used for flavoring curries, as a supplement, and to treat various diseases. This study describes the comparison and discrimination of Garcinia cambogia, Garcinia indica, Garcinia mangostana and Garcinia atroviridis fruits by analyzing their major phytochemicals, elemental content, antioxidant, antidiabetic, and anticholinesterase enzymes activities. For phytochemical and elemental profiling, ultraviolet (UV), near infrared/infrared (NIR/IR), inductively coupled plasma-optical emission spectroscopy (ICP-OES) and ICP-mass spectrometric (ICP-MS) techniques were used. The chemometric multivariate tests of linear discriminant and principal component analyses (LDA, PCA) were used to discriminate the subject fruit samples. Spectroscopic data showed resonances of phenolics and flavonoidal constituents present in the fruits. G. mangostana exhibited the highest phenolics (721.6 to 2815.3 µM GAE/g), whereas G. cambogia was rich in flavonoids (51.9 to 2709.2 µM QE/g). Anthocyanin (cyanidin-3-O-glucoside) evaluated by high performance liquid chromatographic was 9.01 mg/kg in G. mangostana fruit. In the analyzed fruits, Ca, K and Na were high, trace essential elements were at appreciable contents, whereas the toxic elements As, Cd, Tl, and Pb were within the safe limits. G. mangostana contained potent free radicals and cholinesterase enzyme inhibitors, whereas G. cambogia inhibited α-amylase enzyme more significantly. PCA and LDA discriminated the fruit samples with distinct classification and variability indices. The analyzed fruits were shown to be good sources of free radicals, cholinesterase, and α-amylase enzymes inhibition, mineral and essential elements, and safe for human consumption.

    更新日期:2019-11-11
  • Chemiluminescent and Colorimetric Aptamer-Based Assays of Human α-Thrombin
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-14
    Sergei A. Kurseev, Anton M. Solovjev, Marina M. Neumann, Alexey V. Medvedko, Ivan Yu. Sakharov

    A microplate-based sandwich assay for the determination of α-human thrombin (HTb) was developed. Fluorescein-modified 29-mer thrombin binding aptamer (FAM-TBA29) and biotinylated 15-mer thrombin binding aptamer (Bio-TBA15) reacting with different exosites of HTb were used as the biorecognition components in the assay. FAM-TBA29 (capture aptamer) was immobilized using its interaction with anti-fluorescein antibody adsorbed on the microplate surface. As a sensitive signaling system, a combination of Bio-TBA15 and streptavidin-polyHRP conjugate was used. Under the optimized conditions, the detection limit for HTb was 1.4 nM; this value was the same in both the colorimetric and the chemiluminescent assays. The replacement of colorimetry for HRP measurement with chemiluminescence increased the assay sensitivity from 0.06 to 1.7 × 106 nM−1 that clearly demonstrated advantage of the latter approach.

    更新日期:2019-11-11
  • Fluorimetric determination of β-carotene in food samples using a fluorescent dye
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-12
    Catalina Negut Cioates, Jacobus (Koos) Frederick van Staden

    A simple, sensitive, and selective fluorimetric method is reported for the determination of β-carotene in various food samples. Three fluorescent dyes, including fluorescein (F), eosin B (EB), and Congo red (CR), were characterized in a series of measurements to optimize the analytical response for the reliable, suitable, and sustainable determination of β-carotene. 3′,6′-Dihydroxyspiro[isobenzofuran-1(3H),9′-[9H]xanthen]-3-one, commonly known as fluorescein, was selected for the fluorimetric determination of β-carotene using a phosphate buffer. Under the optimum experimental conditions, β-carotene was determined across a range from 0.54 to 536.87 mg L−1 with a detection limit equal to 0.47 mg L−1. The novel method was demonstrated to be easy to use, cost effective, rapid, and less complex compared to a standard protocol that involves a time-consuming extraction followed by an expensive HPLC determination.

    更新日期:2019-11-11
  • A piezoelectric immunosensor for the detection of cortisol.
    Anal. Lett. (IF 1.248) Pub Date : 1995-01-01
    B S Attili,A A Suleiman

    A piezoelectric crystal immunosensor has been developed for the detection and determination of cortisol. Cortisol antibody was layered onto the gold electrodes of a 10 MHz piezoelectric crystal which was pre-coated with either protein A or gluteraldehyde. Crystals pre-coated with protein A showed the best results with respect to stability and sensitivity. The sensor was successfully used for the determination of cortisol in standard solutions from 36-3628 micrograms/L (part per billion). The advantages of the proposed sensor include simplicity, short analysis time, cost effectiveness and selectivity. The results demonstrate the feasibility of cortisol assay in clinical testing and in drug monitoring.

    更新日期:2019-11-01
  • Voltammetric Determination of Dinonyl Diphenylamine and Butylated Hydroxytoluene in Mineral and Synthetic Oil.
    Anal. Lett. (IF 1.248) Pub Date : 2016-07-02
    Yaling Xiang,Xuzheng Qian,Meng Hua,Bingxue Cheng,Wu Chen,Jian Li

    A method is reported for the determination of diphenylamine and butylated hydroxytoluene in mineral and synthetic oil. The procedure used differential pulse voltammetry with a glassy carbon electrode. This method was then used for determining these antioxidants in supporting electrolyte consisting of dilute sulfuric acid and sodium dodecyl sulfonate in ethanol. Anodic peaks were obtained for both analytes. Oxidation peaks at 250 mV were observed from a mixture of butylated hydroxytoluene and dinonyl diphenylamine, allowing their simultaneous determination. This approach was successfully used for the determination of dinonyl diphenylamine and butylated hydroxytoluene in fortified mineral and synthetic oils with good accuracy and precision.

    更新日期:2019-11-01
  • SPECTROSCOPIC AND ELECTROCHEMICAL CHARACTERIZATION OF IRON(II) AND 2,4-DINITROTOLUENE.
    Anal. Lett. (IF 1.248) Pub Date : 2015-01-01
    Kristopher Brown,Hyungie Doo,Honest Makamba,Seong S Seo

    The objective of this work was the development of reliable methods to determine 2,4-dinitrotoluene, a precursor to explosives. A complex between Fe(II) ion and 2,4-dinitrotoluene was formed in solution and characterized by ultraviolet-visible absorption spectroscopy using Job's plots and attenuated total reflection-Fourier transform infrared spectroscopy. Surface modification of glassy carbon electrodes were performed with iron nanoparticles via electrochemical reduction of iron(II). The modified electrode was employed for the determination of 2,4-dinitrotoluene. Scanning electron micrographs showed that the iron nanoparticles were incorporated on the surface of glassy carbon electrode. The electrochemical determination of 2,4-dinitrotoluene was performed by cyclic voltammetry using the modified electrode. The iron modified electrode produced larger reduction currents than the unmodified electrode for the same concentration of 2,4-dinitrotoluene. Concentrations of 2,4-dinitrotoluene as low as 10 parts per billion were determined using the modified electrode.

    更新日期:2019-11-01
  • Determination of Carboxypeptidase Activity in Clinical Pathogens by Gas Chromatography-Mass Spectrometry.
    Anal. Lett. (IF 1.248) Pub Date : 2016-05-27
    Fraser Lough,John D Perry,Stephen P Stanforth,John R Dean

    A novel method for the determination of benzoic acid has been employed to identify carboxypeptidase activities in clinically relevant pathogens. Benzoic acid was determined after chemical derivatization by gas chromatography-mass spectrometry (GC-MS). N-Benzoyl amino acid substrates were evaluated for the detection of carboxypeptidase activities in a number of clinical pathogens. Upon enzymatic hydrolysis of these substrates, benzoic acid was produced which was detected by extraction from the liquid culture supernatant, derivatization as the trimethylsilyl ester, with subsequent analysis by GC-MS. Enzymatic hydrolysis of N-benzoyl glycine was observed for S. agalactiae, M. morganii, and A. baumannii. In addition, P. fluorescens was found to hydrolyze N-benzoyl-L-glutamic acid. Although the method provides an alternative approach for determining carboxypeptidase activity, ultimately it would not be a suitable method in a clinical setting. However, the method is well-suited for identifying carboxypeptidase activities that have not been previously described or to corroborate a carboxypeptidase assay with the ninhydrin reagent.

    更新日期:2019-11-01
  • DIFFERENTIATION OF AURANTII FRUCTUS IMMATURUS AND FRUCTUS PONICIRI TRIFOLIATAE IMMATURUS BY FLOW-INJECTION WITH ULTRAVIOLET SPECTROSCOPIC DETECTION AND PROTON NUCLEAR MAGNETIC RESONANCE USING PARTIAL LEAST-SQUARES DISCRIMINANT ANALYSIS.
    Anal. Lett. (IF 1.248) Pub Date : 2016-03-26
    Mengliang Zhang,Yang Zhao,Peter de B Harrington,Pei Chen

    Two simple fingerprinting methods, flow-injection coupled to ultraviolet spectroscopy and proton nuclear magnetic resonance, were used for discriminating between Aurantii fructus immaturus and Fructus poniciri trifoliatae immaturus. Both methods were combined with partial least-squares discriminant analysis. In the flow-injection method, four data representations were evaluated: total ultraviolet absorbance chromatograms, averaged ultraviolet spectra, absorbance at 193, 205, 225, and 283 nm, and absorbance at 225 and 283 nm. Prediction rates of 100% were achieved for all data representations by partial least-squares discriminant analysis using leave-one-sample-out cross-validation. The prediction rate for the proton nuclear magnetic resonance data by partial least-squares discriminant analysis with leave-one-sample-out cross-validation was also 100%. A new validation set of data was collected by flow-injection with ultraviolet spectroscopic detection two weeks later and predicted by partial least-squares discriminant analysis models constructed by the initial data representations with no parameter changes. The classification rates were 95% with the total ultraviolet absorbance chromatograms datasets and 100% with the other three datasets. Flow-injection with ultraviolet detection and proton nuclear magnetic resonance are simple, high throughput, and low-cost methods for discrimination studies.

    更新日期:2019-11-01
  • MULTIELEMENT SOLID PHASE PRECONCENTRATION USING A CHELATING RESIN OF STYRENE DIVINYLBENZENE COPOLYMER AND APPLICATION TO ANALYSIS OF SEAWATER AND FISH OTOLITHS BY INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY (ICP�MS).
    Anal. Lett. (IF 1.248) Pub Date : 2014-07-01
    Fahmida Zereen,Vedat Yilmaz,Zikri Arslan

    A new chelating resin has been synthesized by immobilizing 4-(2-thiazolylazo) resorcinol (TAR) onto styrene divinlybenzene copolymer and examined for on-line solid phase extraction/preconcentration of Cd, Co, Cu, Ni, Pb and Zn in seawater and fish otoliths for determination by inductively plasma mass spectrometry (ICP-MS). A volume of 5.0 mL sample solution was loaded onto the mini column of TAR immobilized resin at 2.0 mL min-1 via a sequential injection system. The optimum pH for multielement preconcentration was around pH 5.5. Recoveries were better than 96% in artificial seawater. Elution was achieved with 1.0 mL of 0.75 mol L-1 HNO3. The resin possesses large sorption capacity ranging from 82.0 µmol g-1 for Pb to 319 µmol g-1 for Cu. The detection limits (3s) varied between 0.0016 µg L-1 (Cd) and to 0.015 µg L-1 (Zn) for preconcentration of 5.0 mL blank solutions (pH 5.5). Relative standard deviation (RSD)for three replicate runs was between 0.3% (Cd) and 6% (Zn) at 1.0 µg L-1 level. The procedure was validated by analysis of Nearshore Seawater certified reference material (CASS-4), and then successfully applied to the determination of the trace elements in fish otoliths (CRM 22) and in coastal seawater and estuarine water samples.

    更新日期:2019-11-01
  • Preparation of PbS Nanoparticles by Phase-Transfer Method and Application to Pb-Selective Electrode Based on PVC Membrane.
    Anal. Lett. (IF 1.248) Pub Date : 2008-12-30
    Weihong Song,Chunhui Wu,Hongzong Yin,Xiaoyan Liu,Panpan Sa,Jinyang Hu

    A novel approach to prepare homogeneous PbS nanoparticles by phase-transfer method was developed. The preparatory conditions were studied in detail, and the nanoparticles were characterized by transmission electron microscopy (TEM) and UV-vis spectroscopy. Then a novel lead ion-selective electrode of polyvinyl chloride (PVC) membrane based on these lead sulfide nanoparticles was prepared, and the optimum ratio of components in the membrane was determined. The results indicated that the sensor exhibited a wide concentration range of 1.0x10(-5) to 1.0x10(-2) mol.L(-1). The response time of the electrode was about 10 s, and the optimal pH in which the electrode could be used was from 3.0 to 7.0. Selectivity coefficients indicated that the electrode was selective to the primary ion over the interfering ion. The electrode can be used for at least 3 months without any divergence in potential. It was successfully applied to directly determine lead ions in solution and used as an indicator electrode in potentiometric titration of lead ions with EDTA.

    更新日期:2019-11-01
  • Quantum Dots as Reporters in Multiplexed Immunoassays for Biomarkers of Exposure to Agrochemicals.
    Anal. Lett. (IF 1.248) Pub Date : 2007-01-01
    M Nichkova,D Dosev,A E Davies,S J Gee,I M Kennedy,B D Hammock

    The application of quantum dots (QDs) as labels in immunoassay microarrays for the multiplex detection of 3-phenoxybenzoic acid (PBA) and atrazine-mercapturate (AM) has been demonstrated. PBA and AM are biomarkers of exposure to the pyrethroid insecticides and to the herbicide atrazine, respectively. Microarrays were fabricated by microcontact printing of the coating antigens in line patterns onto glass substrates. Competitive immunoassays were successfully performed using QDs (QD560 and QD620) as reporters. The multiplexed immunoassays were characterized by fluorescence microscopy and SEM. The application of QD fluorophores facilitates multiplex assays and therefore can contribute to enhanced throughput in biomonitoring.

    更新日期:2019-11-01
  • A Robust Analytical Approach for the Identification of Specific Protein Carbonylation Sites: Metal-Catalyzed Oxidations of Human Serum Albumin.
    Anal. Lett. (IF 1.248) Pub Date : 2017-03-18
    Zafer Ugur,Scott Gronert

    The formation of protein carbonyls in the metal-catalyzed oxidation of human serum albumin (HSA) is characterized using a new analytical approach that involves tagging the modification site with multiple hydrazide reagents. Protein carbonyl formation at lysine and arginine residues was catalyzed with copper and iron ions, and the resulting oxidation patterns in HSA are contrasted. A total of 18 modification sites were identified with iron ion catalysis and 14 with copper ion catalysis. However, with the more stringent requirement of identification with at least two tagging reagents, the number of validated modification sites drops to 10 for iron and 9 for copper. Of the 14 total validated sites, there were only five in common for the two metal ions. The results illustrate the value of using multiple tagging agents and highlight the selective and specific nature of metal-catalyzed protein oxidations.

    更新日期:2019-11-01
  • Novel Imprinted Polymer for the Preconcentration of Cadmium with Determination by Inductively Coupled Plasma Mass Spectrometry.
    Anal. Lett. (IF 1.248) Pub Date : 2017-02-28
    Vedat Yilmaz,Hayriye Yilmaz,Zikri Arslan,Jerzy Leszczynski

    A novel Cd(II)-imprinted polymer was prepared with chemical immobilization approach by using N-methacryloyl-L-histidine as a vinylated chelating agent for on-line solid phase extraction of Cd(II) for determination by inductively coupled plasma mass spectrometry. Cd(II)-monomer complex was synthesized and copolymerized via bulk polymerization method in the presence of ethyleneglycoldimethacrylate cross-linker. The resulting polymer was leached with 1.0 mol L-1 HNO3 to generate the cavities in the polymer for Cd(II) ions. The experimental conditions, including load pH, solution flow rate, and eluent concentration for effective sorption of Cd(II) were optimized using a minicolumn of the imprinted polymer. A volume of 5.0 mL sample 5 μg L-1 Cd(II) solution at pH 6.5 was loaded onto the column at 2.0 mL min-1 by using a sequential injection system (FIALab 3200) followed by elution with 1.0 mL of 0.75 mol L-1 HNO3. The relative selectivity coefficients of the imprinted polymer for Cd(II) were 38.5, 3.5, 3.0, 2.5 and 6.0 in the presence of Cu(II), Ni(II), Zn(II), Co(II) and Pb(II), respectively. Computational calculations revealed that the selectivity of the imprinted polymer was mediated by the stability of Cd(II)-N-methacryloyl-L-histidine complex which was far more stable than those of commonly used monomers, such as 4-vinyl pyridine, methacrylic acid and vinylimidazole. The detection limit (3s) and relative standard deviation (%) were found to be 0.004 μg L-1 and 3.2%, respectively. The method was validated by analysis of seawater certified reference material (CASS-4) and successfully applied to the determination of Cd(II) in coastal seawater and estuarine water samples.

    更新日期:2019-11-01
  • Characterization of Zinc Carbonate Basic as a Source of Zinc in a Rodent Study Investigating the Effects of Dietary Deficiency or Excess.
    Anal. Lett. (IF 1.248) Pub Date : 2017-01-01
    Keith E Levine,Bradley J Collins,Matthew D Stout,Michael Wyde,Scott E Afton,Amal S Essader,Todd J Ennis,Kelly E Amato,Andrea C McWilliams,Brenda L Fletcher,Reshan A Fernando,James M Harrington,Natasha Catlin,Veronica G Robinson,Suramya Waidyanatha

    Zinc deficiency and excess can result in adverse health outcomes. There is conflicting evidence regarding whether excess or deficient zinc in the diet can contribute to carcinogenicity. The objective of this study was to characterize zinc carbonate basic for use as a source of dietary zinc in a rodent toxicity and carcinogenicity study investigating the effects of zinc deficiency and excess. Because of the complex chemistries of zinc carbonate basic compounds, inconsistent nomenclature, and literature and reference spectra gaps, it was necessary to employ multiple analytical techniques, including Karl Fischer titration, combustion analysis, inductively coupled plasma-optical emission spectrometry, X-ray diffraction, infrared spectroscopy, X-ray fluorescence spectrometry, and thermogravimetric analysis to characterize the test article. Based on the collective evidence and through the process of elimination, the test article was found to be composed mainly of zinc carbonate basic with zinc oxide as a minor component. The zinc content was determined to be 56.6% (w/w) with heavy metals such as arsenic, cadmium, mercury and lead below the limit of quantitation of less than or equal to 0.01%. The test material was stable at ambient temperature. Based on the work described in this manuscript, the test article was suitable for use as a source of zinc in studies of deficiency and excess in the diet.

    更新日期:2019-11-01
  • VARIABLE SELECTION AND BIOMARKER CORRELATION IN THE ANALYSIS OF MYCOPLASMA PNEUMONIAE STRAINS BY SURFACE-ENHANCED RAMAN SPECTROSCOPY.
    Anal. Lett. (IF 1.248) Pub Date : 2017-01-01
    Duncan C Krause,Suzanne L Hennigan,Kelley C Henderson,Harrison J Clark,Richard A Dluhy

    Mycoplasma pneumoniae is a human respiratory tract pathogen causing chronic bronchitis and atypical or "walking" pneumonia. The major surface protein P1 must form complexes with proteins P30 and P40/P90 in order to function in receptor binding and gliding motility, and variability in P1 and P40/P90 distinguishes the two major M. pneumoniae genotypes. Strains belonging to each genotype can be differentiated with high sensitivity and specificity by utilizing surface-enhanced Raman spectroscopy on silver nanorod arrays. Here we used the variable selection method of Variable Importance in Projection (VIP) to identify Raman bands important in M. pneumoniae strain classification. Furthermore, VIP analysis of mutants lacking P40/P90, or P1and P40/P90, correlated certain Raman bands important in distinguishing genotypes, with specific mycoplasma surface protein composition and presentation. Variable selection, and its correlation with specific mycoplasma surface components, is an important next step in developing this platform for M. pneumoniae detection and genotyping.

    更新日期:2019-11-01
  • Voltammetric Application of Polypyrrole-Modified Microelectrode Array for the Characterization of DNA Methylation in Glutathione S-Transferase Pi 1.
    Anal. Lett. (IF 1.248) Pub Date : 2018-09-25
    Kenton Meronard,Mira Josowicz,Amir Saheb

    Direct and efficient label-free voltammetric detection of Glutathione S-Transferase Pi 1 (GSTP1) hypermethylation is reported using a custom developed 16-channel Microelectrode Array chip. The microelectrode array chip is used in a dipstick configuration allowing detection of DNA hybridization in a solution volume of only 0.35 mL. Platinum microelectrode disks (n = 16) 30 µm in diameter have been modified with a polypyrrole bilayer before any contact with the oligonucleotides. The attachment of the 15-mer Probe DNA to the bilayer is random but controlled by the presence of aliphatic tether groups allowing it to form a bidentate complex with the probe DNA. The voltammetric detection procedure of methylated GSTP1-specific target DNA is combined with bisulfite treatment of target DNA. Changes at the interface of the modified microelectrodes in an array configuration are used to record simultaneously cyclic voltammetry on all of the devices. The detection of the hybridization is evaluated statistically for a yes or no event by comparing the changes in recorded cyclic voltammograms before and after exposure to the Target DNA. All cyclic voltammograms of the methylated target show a greater percentage change than those with the non-methylated target exposure and show a greater change in cyclic voltammogram area after methylated target exposure. We observe an average percentage difference of 25.6% ± 4.9 with a variation of 19.1%. These results demonstrate that the fast sensing strategy possesses sensitivity and good specificity. Furthermore, this technology can potentially support rapid, accurate diagnosis and risk assessment of patients with prostate cancer.

    更新日期:2019-11-01
  • RECENT DEVELOPMENTS IN ELECTROCHEMICAL SENSORS FOR THE DETECTION OF NEUROTRANSMITTERS FOR APPLICATIONS IN BIOMEDICINE.
    Anal. Lett. (IF 1.248) Pub Date : 2016-03-15
    Rıfat Emrah Özel,Akhtar Hayat,Silvana Andreescu

    Neurotransmitters are important biological molecules that are essential to many neurophysiological processes including memory, cognition, and behavioral states. The development of analytical methodologies to accurately detect neurotransmitters is of great importance in neurological and biological research. Specifically designed microelectrodes or microbiosensors have demonstrated potential for rapid, real-time measurements with high spatial resolution. Such devices can facilitate study of the role and mechanism of action of neurotransmitters and can find potential uses in biomedicine. This paper reviews the current status and recent advances in the development and application of electrochemical sensors for the detection of small-molecule neurotransmitters. Measurement challenges and opportunities of electroanalytical methods to advance study and understanding of neurotransmitters in various biological models and disease conditions are discussed.

    更新日期:2019-11-01
  • RECENT ADVANCES IN ULTRA-HIGH PERFORMANCE LIQUID CHROMATOGRAPHY FOR THE ANALYSIS OF TRADITIONAL CHINESE MEDICINE.
    Anal. Lett. (IF 1.248) Pub Date : 2014-07-22
    Huilian Huang,Min Liu,Pei Chen

    Traditional Chinese medicine has been widely used for the prevention and treatment of various diseases for thousands of years in China. Ultra-high performance liquid chromatography (UHPLC) is a relatively new technique offering new possibilities. This paper reviews recent developments in UHPLC in the separation and identification, fingerprinting, quantification, and metabolism of traditional Chinese medicine. Recently, the combination of UHPLC with MS has improved the efficiency of the analysis of these materials.

    更新日期:2019-11-01
  • Novel Enzyme-Linked Aptamer Assay for the Determination of Aflatoxin B1 in Peanuts
    Anal. Lett. (IF 1.248) Pub Date : 2019-06-26
    Yanli Xie, Mengge Ning, Jun Ban, Qian Li

    A novel enzyme-linked aptamer assay is reported for the determination of aflatoxin B1 (AFB1). AFB1 can competitively bind with the immobilized biotin-aptamer and release biotin complementary DNA, leading to the gradual fading of the detection system color with increasing of AFB1 concentration. In the absence of AFB1, the biotinylated complementary DNA is not be released from the fixed aptamer. Therefore, the enzyme reaction occurs in the detection system. Under the optimized experimental conditions, the proposed method possessed a wide linear range for AFB1 from 1 to 80 ng/mL (R2 of 0.990) with a low detection limit of 0.36 ng/mL. The method was then applied to detect uncontaminated peanuts fortified with different concentrations of AFB1. The recovery values were from 82.60% to 94.43%, which indicated the proposed method may be used to detect AFB1 in food and has potential for the development of test kits.

    更新日期:2019-10-25
  • Large Volume Sample Stacking (LVSS) in Capillary Electrophoresis (CE) with Response Surface Methodology (RSM) for the Determination of Phenolics in Food Samples
    Anal. Lett. (IF 1.248) Pub Date : 2019-06-06
    Almas F. Memon, Ismail M. Palabiyik, Amber R. Solangi, Saima Q. Memon, Arfana B. Mallah

    A capillary electrophoresis method with large volume sample stacking (CE-LVSS) has been developed and validated for the simultaneous determination of seven phenolic compounds: naringin, rutin, carnosic acid, apigenin, quercetin, morin, and chichoric acid. Optimization was carried out by response surface methodology and a set of 20 experiments helped to optimize the parameters such as the concentration of buffer, buffer pH, and applied voltage. Analytes were separated using a 50 µm diameter capillary with 56 cm effective length and an extended light path using 20 mM borate buffer at pH 9.2. The LVSS method was optimized and a three- to fivefold improvement in detectability was achieved with injection at 100 mbar for 20 s followed by polarity switching at –20 kV for 6 s. The linearity values of all seven analytes were observed in the concentration ranges from 0.5 to 50 µg/mL for CE and 0.1 to 25 µg/mL for LVSS. The limits of detection were from 0.012 to 0.241 and 0.003 to 0.086 µg/mL for CE and LVSS. The obtained limits of quantitation were within 0.041 to 0.802 for CE and 0.012 to 0.286 µg/mL for LVSS. The recoveries were between 91.1 and 109.8% and 96.3 and 108.4% for CE and LVSS, respectively. The developed method has been successfully applied for the quantitative determination of analyzed components from food samples that are important sources of these compounds.

    更新日期:2019-10-25
  • Enhanced Surface-Enhanced Raman Scattering (SERS) Sensitivity by the Self-Assembly of Silver Nanoparticles (Ag NPs) Laminated on Polydimethylsiloxane (PDMS)
    Anal. Lett. (IF 1.248) Pub Date : 2019-06-08
    Lele Zhu, Hui Dai, Shuyun Zhang, Die Hu, Qun Zhou, Mingqiang Zou, Jason Adkins, Junwei Zheng

    Herein, a transparent and reproducible substrate, fabricated using polydimethylsiloxane (PDMS) laminated with self-assembled Ag nanoparticles (Ag NPs), was employed as a universal surface-enhanced Raman scattering (SERS) substrate for the detection of targets with various matrices. The Ag NPs were assembled in a two-dimensional manner via a self-assembly technique. Due to the electrostatic interaction between the Ag NPs, the reproducibility of the assembly was ensured by the fixed density of the assembled Ag NPs at saturated assembly states. The assembled pattern and plasmon resonance of the Ag NPs were well preserved during the molding and curing of PDMS. As a result, the Ag NP laminated PDMS film exhibited a SERS effect to the adsorbed p-aminothiophenol comparable to that of the assembled Ag NPs on a glass slide. Extra SERS enhancement was achieved by construction of a Ag (PDMS)/molecule/Ag (glass) configuration due to the electromagnetic coupling between the Ag NPs. The Raman scattering of 4-mercaptobenzoic acid and benzotriazole modified on the surfaces of a smooth Au electrode and copper foil, respectively, was detected with the aid of the Ag NP-laminated PDMS film. Furthermore, malachite green dispersed in a KBr solid matrix was quantitatively determined with a detection limit of 0.5 μg/g. It is suggested that the SERS enhancement and consequential SERS detection sensitivity of the target molecules may be further maximized by adjusting the distance between the target molecules and the Ag NPs laminated on the PDMS film.

    更新日期:2019-10-25
  • Electrochemical amplification for Hg(II) quantification by anchoring an enzymatically extended aptamer
    Anal. Lett. (IF 1.248) Pub Date : 2019-06-12
    Xiaoxi Si, Shiyun Tang, Kunmiao Wang, Guofu Zhou, Jianjun Xia, Yang Zhao, Hui Zhao, Qinpeng Shen, Zhihua Liu

    A novel indirect electrochemical approach is reported to improve the sensitivity of Hg2+ quantification in environmental water samples. This strategy is based on the Hg2+ induced selective interaction of thymine mismatched pairs in a thymine-rich aptamer DNA to improve the specificity, while template-independent terminal deoxynucleotidyl transferase (TdT) extended the 3′-OH aptamer termini with repeated bases and increased the sensitivity. The introduction of the target Hg2+ blocked aptamer extension. Taking advantage of an electrochemical platform, this aptamer-TdT based amplification sensor enabled the specific quantification of Hg2+ ion over a wide linear range from 2 pM to 20 nM with a low limit of detection equal to 0.1 pM. The proposed strategy is promising for the detection of other metal ions.

    更新日期:2019-10-25
  • Solid-phase extraction using a molecularly imprinted polymer for the selective purification and preconcentration of norfloxacin from seawater
    Anal. Lett. (IF 1.248) Pub Date : 2019-06-20
    Huiping Li, Jianlei Chen, Liju Tan, Jiangtao Wang

    A highly selective and effective method for the purification and preconcentration of norfloxacin (NFX) in seawater samples was developed based on molecularly imprinted solid-phase extraction (MISPE). The molecularly imprinted polymer was synthesized by precipitation polymerization. Methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) were used as the functional monomer and crosslinker, respectively. The resulting molecularly imprinted polymer (MIP) showed high adsorption for NFX and was selective for its solid-phase extraction. An offline MISPE method followed by high performance liquid chromatography with diode array detection was established for the determination of NFX in seawater. The recoveries of spiked seawater samples using the MISPE columns were satisfactorily higher than 77.6%. The relative standard deviation was less than 5.60%, and the limit of detection was 0.027 μg L−1. Four seawater samples obtained from the Bohai Sea were analyzed, and NFX was found only at one location at a concentration of 0.280 μg L−1.

    更新日期:2019-10-25
  • Determination of API Gravity and Total and Basic Nitrogen Content by Mid- and Near-Infrared Spectroscopy in Crude Oil with Multivariate Regression and Variable Selection Tools
    Anal. Lett. (IF 1.248) Pub Date : 2019-06-19
    Karla Pereira Rainha, Júlia Tristão do Carmo Rocha, Rayza Rosa Tavares Rodrigues, Betina Pires de Oliveira Lovatti, Eustáquio Vinicius Ribeiro de Castro, Paulo Roberto Filgueiras

    American Petroleum Institute (API) gravity is an important parameter in the crude oil industry and the nitrogen compounds are related to the toxic effects of the oil in refineries and the environment. In this paper, 194 crude oil samples with API gravities ranging from 11.4 to 57.5 were used for the purpose of estimating the physicochemical properties: API gravity, total nitrogen content (TNC) and basic nitrogen content (BNC). Initially, infrared spectra in the mid and near regions (MIR and NIR) were collected, then full-spectral partial least squares (PLS) and the orthogonal projections to latent structures (OPLS) chemometric models were developed and validated, as well as models using interval PLS (iPLS), synergy interval PLS (siPLS) and competitive adaptive reweighted sampling PLS (CARSPLS) as variable selection tools. For API gravity and TNC, the best calibration technique is the NIR CARSPLS with a root mean square error of prediction (RMSEP) values of 0.9 and 0.0275 wt%, respectively. For BNC, the best technique is MIR siPLS with a prediction error of 0.0134 wt%. The results were validated based on the evaluation of the figures of merit, a statistical evaluation of the accuracy, characterization of the systematic error and measurement for errors in the residues. The results were satisfactory considering the high variability of the data and the diversity of the samples, demonstrating suitable applicability for practical analysis.

    更新日期:2019-10-25
  • Compositional Analysis of Cement Raw Meal by Near-Infrared (NIR) Spectroscopy
    Anal. Lett. (IF 1.248) Pub Date : 2019-06-11
    Hang Xiao, Zhenfa Yang, Lei Zhang, Dejun Feng, Faye Zhang, Mingshun Jiang, Qingmei Sui, Lei Jia

    A rapid and accurate method is presented to determine CaCO3, SiO2, Fe2O3, and Al2O3 in cement raw meal using near-infrared (NIR) spectroscopy. Multiplicative scatter correction (MSC) was employed to eliminate the scattering signal and partial least squares (PLS) regression was used to build the analysis model. The results demonstrated good performance by this approach for the determination of CaCO3, SiO2, Fe2O3, and Al2O3. NIR spectroscopy exhibits the feasibility to characterize the quality of cement raw meal. Compared with prompt gamma neutron activation analysis (PGNAA) and X-ray fluorescence (XRF), this method is more efficient and safer.

    更新日期:2019-10-25
  • Oligonucleotide Functionalized Microporous Gold Electrode for the Selective and Sensitive Determination of Mercury by Differential Pulse Adsorptive Stripping Voltammetry (DPAdSV)
    Anal. Lett. (IF 1.248) Pub Date : 2019-06-25
    Xu Yiwei, Li Zhihua, Zhang Wen, Shi Jiyong, Zou Xiaobo, Huang Xiaowei, Hu Xuetao, Wang Xin

    A novel electrode modified with oligonucleotide and microporous gold was fabricated for the determination of mercury by differential pulse adsorptive stripping voltammetry (DPAdSV). Microporous gold was synthesized by electrochemical reduction using dynamic hydrogen bubble template. The oligonucleotide was immobilized on microporous gold by self-assembly. The prepared electrode exhibited an improved electrochemical response for mercury(II) ion because of the large surface area and excellent electron transfer capacity provided by microporous gold and the specific coordination between mercury ion and thymine bases in oligonucleotides. Under the optimal experiment conditions, the oligonucleotide functionalized microporous gold electrode had a linear relationship between the stripping current and mercury ion concentration in the range from 0.5 to 30 µg/L with a detection limit of 0.021 µg/L. Moreover, the prepared electrode exhibited good selectivity, reproducibility, repeatability and stability. Furthermore, the prepared electrode was applied to detect mercury in tap water with satisfactory results.

    更新日期:2019-10-25
  • Determination of Polybrominated Diphenyl Ethers (PBDEs) in Freshwater Fish Around a Deca-brominated Diphenyl Ether (deca-BDE) Production Facility by Gas Chromatography-Mass Spectrometry (GC-MS)
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-08
    Nankun Li, Juan Luo, Situ Na, Shuai Du, Xiaohui Wang, Reti Hai

    Polybrominated diphenyl ethers (PBDEs) were determined in 36 fish samples near a deca- brominated diphenyl ether (deca-BDE) production facility in Weifang City, Shandong Province, China. The concentrations of PBDEs in fish muscle and liver samples were from 45.8 to 560 ng g−1 lipid weight (lw) and 327 to 2120 ng g−1, lw, respectively. The highest concentration of PBDEs was found in carp with a mean value of 1370 ng g−1, lw, followed by crucian with a mean of 1030 ng g−1, lw, and grass carp with a mean of 681 ng g−1, lw. Relatively constant congener patterns were observed among the fish species. BDE-47 was the most predominant congener with contributions of 50.1% to 89.7% to the total PBDE concentrations. Different BDE-99/BDE-100 ratios were observed, indicating that the PBDE pattern is species-dependent.

    更新日期:2019-10-25
  • Determination of Aromatic Amines in Urine using Extraction and Chromatographic Analysis: A Minireview
    Anal. Lett. (IF 1.248) Pub Date : 2019-07-03
    Boon Yih Hui, Nur Nadhirah Mohamad Zain, Sharifah Mohamad, Hafizuddin Mohamed Fauzi, Yatimah Alias, Kumuthini Chandrasekaram, Nurul Yani Rahim, Noorfatimah Yahaya, Muggundha Raoov

    Aromatic amines found in tobacco smoke are carcinogenic to humans. There are no doubts that they cause of cancers in the lungs, bladder, kidneys, pancreas, esophagus, larynx, pharynx, and oral cavities associated with public health. Therefore, monitoring, control, and awareness toward the smoking effects are important subjects to be conveyed. Thus, rapid, sensitive, simple and accurate analytical methods for the identification of aromatic amines and their metabolites are required to provide a clear and complete visualization for the occurrence of aromatic amines by investigating the urine of smokers and nonsmokers. This comprehensive review serves to give an overview of the previous and recent studies about the analytical trends for the determination of urinary aromatic amines. This review covers the sampling methodologies and sample preparation techniques such as solvent extraction, solid phase extraction, magnetic solid phase extraction, and solid phase microextraction couple with different separation methods including gas chromatography and liquid chromatography. To add more value to this review paper, the advantages, disadvantages, challenges, and the future prospects of these methods are discussed as well. This review is hopefully beneficial for researchers to access and monitor the level of potentially carcinogenic aromatic amines in human urine.

    更新日期:2019-10-25
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