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Hierarchically bimetallic Zr-Cu metal–organic framework combined with 1,3,5-benzenetricarboxylic acid (Zr-CuBTC MOFs) was synthesized using hydrothermal reaction and used as modifier for investigation of non-electroactive glyphosate. These MOFs were dropcasted on a glassy carbon electrode (GCE) and non-electroactive glyphosate were tested by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). Glyphosate in water was recognized by the difference of currents in spiked and non-spiked glyphosate samples. At the same time, CuBTC and Fe-CuBTC were investigated for the best material for sensor development. The results showed the bimetallic Zr-CuBTC MOF is the most promising for the determination of glyphosate. Morphological and structural studies showed the coordination of Cu2+ with the presence of Zr4+ ions with BTC ligands provided a highly porous framework with active surface area up to 1337 m2 g−1. The pore diameter and pore volume increased to 1.75 nm and 0.687 cm3 g−1, respectively. Under optimal conditions, Zr-CuBTC modified on GCE (Zr-CuBTC/GCE) sensor is able to indirectly detect glyphosate in a water environment at a detection limit as low as 9 × 10−13 M. The developed sensor was employed to determine glyphosate in the surface water samples collected from the Red River, North Vietnam. The results showed good recoveries (94.6–107.1%) which were in agreement with liquid chromatography coupled tandem mass spectrometry (LC-MS/MS) measurements. These results demonstrate the possibility of using this MOF material in sensor applications to determine trace pesticides in the contaminated water. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) in the air are one of the major concerns due to their possible health risks. In addition, airborne microplastics act as a carrier for several toxic air pollutants and cause carcinogenic, mutagenic and teratogenic effects. Nylon 66 is one of the most abundant MPs in the microenvironments. In this study, we report an optimized method for the quantification of nylon 66 MPs present in the fine particulate matter (PM2.5) using high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS). The optimized method exhibited excellent linearity, recovery rates, intraday and interday precision and sensitivity. The optimized method was deployed to carry out a pilot study to measure the mass concentrations of nylon 66 microplastics present in the inhalable fraction of particulate matter collected in a shopping complex. The observed mass concentrations of nylon 66 MPs in this study are in the range from 0.30 ng m−3 to 4.37 ng m−3. This study demonstrates the presence of inhalable fraction of nylon 66 MPs in the indoor environment and their mass concentrations were determined using HPLC-MS/MS. [ABSTRACT FROM AUTHOR]

Matrix effects are a major concern in liquid chromatography coupled to tandem mass spectrometry for the determination of pesticide residues. In this work, a novel and efficient lipophilicity-matched chromatographic separation strategy was developed to improve the separation efficiency on an alkyl bonded phase chromatographic column and reduce matrix effects. An ultra-high performance liquid chromatography-tandem mass spectrometry method based on this strategy was established to minimize matrix effects for the determination of triazole fungicides. The samples were cleaned-up with dispersive solid phase extraction and separated on a chromatographic column with similar lipophilicity to the fungicides. The results showed that the proposed method effectively minimized the matrix effects and improved the separation. The matrix effects of 21 fungicides ranged from −8.3% to 4.7%. Moreover, the average recoveries were between 91.4% and 108.1% using solvent calibration for quantification, and the limits of quantitation were between 0.5 and 3.5 μg/kg. These results demonstrate the effectiveness of the proposed strategy in improving the chromatographic efficiency. This work provides a practical strategy and reference for the liquid chromatography-tandem mass spectrometry determination of pesticide residues. [ABSTRACT FROM AUTHOR]

Organic acids are among the primary substances affecting the flavor of 'Fenjiao' bananas. Several previous studies have characterized organic acids and their corresponding biosynthetic pathways in 'Fenjiao' bananas; however, chemical information about the spatial and temporal distributions of the organic acids in the bananas is absent. In this study, air flow-assisted desorption electrospray ionization mass spectrometry imaging (AFADESI-MSI) for analyzing organic acids in 'Fenjiao' bananas was developed. The organic acids in the peel and pulp of 'Fenjiao' bananas were detected and imaged in situ, and the spatial distribution of organic acids in banana fruit tissue slices were visualized. The results were validated by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results showed that the MSI method can provide more accurate spatial and chemical localizations of the four primary organic acids (i.e., citric, malic, fumaric, and quinic acids) in the same tissues of 'Fenjiao' bananas. However, the quantification of the concentrations in different tissues is adversely affected by inaccuracy due to matrix effects. The in situ determination of the organic acids in 'Fenjiao' bananas can assist to understand the spatial and temporal distribution of organic acids in bananas, which provides a new method and idea to explore the biosynthesis and accumulation pattern of metabolites. [ABSTRACT FROM AUTHOR]

A sensor based on graphite nanosheets was fabricated through the electrochemical expansion of a graphite electrode in dimethyl sulfoxide for the sensitive electrochemical determination of enrofloxacin. The modified electrode surface exhibited a distinctive structure of nanoplates, characterized by layer thickness ranging from a few nanometers to ten nanometers. The developed electrode displayed notable electrochemical properties, including a faster charge transfer rate and a larger electrochemically active surface area, which was 1.3 times greater compared to the unmodified electrode. As a result, the sensor improved square wave voltammetric signals for enrofloxacin, exhibiting a 2.4-fold enhancement compared to the unmodified electrode. By optimizing the experimental parameters such as electrode fabrication conditions, pH of analytical solution, and adsorption time for enrofloxacin, the sensor demonstrated good reproducibility and a strong linear correlation over two ranges of enrofloxacin concentrations from 0.05–0.15 μM and 0.1–20 μM. The limit of detection was determined to be 0.002 μM. The sensor was successfully employed for the determination of enrofloxacin in spiked surface water samples before and after treating enrofloxacin by a photocatalytic method. The obtained results exhibited consistency with those obtained using a liquid chromatography-tandem mass spectrometry reference method, and a high recovery rate of 105.5% further confirmed the reliability of the proposed method for enrofloxacin detection. [ABSTRACT FROM AUTHOR]

This study established a simple, rapid, and sensitive ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for the simultaneous quantification of contezolid and its major metabolite M2 in human plasma and cerebrospinal fluid (CSF). We used isotope-labeled internal standards (IS) along with protein precipitation to efficiently eliminate impurities. The ion transition was m/z 409.1 → 269.1 for contezolid, m/z 414.1 → 269.0 for contezolid-d5, m/z 445.1 → 385.1 for M2, and m/z 450.2 → 390.1 for M2-d5. The flow rate was 0.4 mL/min with a run time of 2.5 min. Validation results demonstrated that the calibration range was 10–5000 ng/mL for contezolid, and 5–2500 ng/mL for M2 in plasma and CSF. Both analytes exhibit excellent linear relationships (all R2 ≥ 0.99). Intra- and inter-batch accuracy and precision for all quality control (QC) levels were within ± 15%, including the lower limit of quantification (LLOQ). The recoveries of contezolid and M2 were 92.60–100.4% and 92.26–99.61% in plasma and 93.33–99.19% and 91.31–98.21% in CSF, respectively. The matrix effects for contezolid and M2 were 97.20–110.3% and 98.27–105.47% in plasma and 105.25–112.99% and 103.35–109.84% in CSF, respectively. The coefficients of variation (CV%) were ≤ 12.58%. Conteozolid and M2 remained stable in plasma and CSF. This study has established a simple and accurate method for determining contezolid and M2 in human plasma and CSF, making it a valuable tool for monitoring the efficacy of central nervous system (CNS) drugs. [ABSTRACT FROM AUTHOR]

Per- and polyfluoroalkyl substances (PFAS) are known to bioaccumulate in aquatic organisms, such as shellfish, and have been linked to adverse human health outcomes. Increasing attention has been focused on method development for the detection of PFAS in various media; however, these methods are typically tedious, require high solvent volumes, and are time consuming. The present method used a Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extraction approach and analysis by ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) to detect 28 PFAS in Eastern oyster (Crassostrea virginica) tissue. This method was validated using limit of detection, limit of quantitation, and precision and accuracy studies. Limits of detection ranged from 0.2 to 5.8 ng g−1, limits of quantitation ranged from 0.66 to 19.2 ng g−1, and recoveries spanned 52.1–105.9% at the 100 ng mL−1 analyte level. Analysis of 12 unknown oyster composite samples revealed the detection of PFHxA, PFPeS, PFOA, PFHpA and PFOS and at least two compounds were detected in each oyster sample. This validated method proved to be an efficient and environmentally friendly sample preparation method for PFAS analysis in complex tissue media, such as oysters. [ABSTRACT FROM AUTHOR]

As a common pharmaceutical plant, Angelica sinensis (called Danggui (DG) in Chinese) is widely used in food, pharmaceuticals, and cosmetics and frequently processed with rice wine. Eight batches of rice wine-processed (WDG) samples and unprocessed DG were prepared to compare the chemical component differences. High-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF-MS) was combined with a molecular network strategy. The 140 components were identified, thereby providing a comprehensive characterization of DG and WDG. Chemometrics was used to compare the variations in these components, and the results revealed higher abundances of certain amino acids and organic acids in WDG. These differences may explain the higher efficacy of WDG. This study shows the differences between DG and WDG included variation in the content, which provides a basis for the study of WDG and support for the standardization of Chinese medicine processing. [ABSTRACT FROM AUTHOR]

Trichothecenes (deoxynivalenol, 3- and 15-acetyl-deoxynivalenol) and zearalenone are toxic secondary metabolites produced by Fusarium species. Although managing these mycotoxins simultaneously is crucial, current analytical methods differ because of their distinct properties. In this study, food matrix extraction conditions were established and applied to cereal-based foods (n = 90). The optimal conditions were developed by utilizing fragment ions and precursors, following the guidelines established by the Association of Official Agricultural Chemists (AOAC). The developed method demonstrated high accuracy and reliability within 20 min, even for samples with low concentrations. Consequently, the recovery range of the fat-oil-processed products and cereal sirup improved from 27.0% to 98.3% and 27.6% to 97.8%, respectively. This improved extraction method offers a more convenient and rapid approach for the analysis of various matrices. Furthermore, these optimized methods can be extended to monitor the co-occurrence of mycotoxins in cereal-based foods, providing valuable assistance to the food industry and regulatory agencies for detecting and monitoring mycotoxins that may pose potential health risks. [ABSTRACT FROM AUTHOR]

Farfarae Flos (FF), also known as "Kuandonghua" in Chinese, is a commonly used traditional Chinese medicine (TCM) with various therapeutic properties, including antitussive, expectorant, antioxidant, and anti-inflammatory effects. Despite the widespread consumption of processed FF, there has been limited progress in improving quality control measures for both raw FF and honey-processed Farfarae Flos (PFF). This study aimed to establish a comprehensive strategy for quality evaluation and distinguish between FF and PFF by integrating high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis with chemometric techniques. Additionally, the antioxidant activities of FF and PFF were assessed using radical-scavenging experiments. The spectrum-effect relationship is the association of chemical composition information of the fingerprint with antioxidant activity, which was used to predict the primary active components that influence the antioxidant activity of FF. The results indicated that FF and PFF samples showed a clear distinction, and the most potent pharmacologically active ingredients were hyperoside, quercetin, caffeic acid, isoquercitrin, neochlorogenic acid, rutin, cryptochlorogenic acid, and isochlorogenic acid C. Moreover, the comprehensive efficacy of the honey-processed FF was better than for raw FF. In conclusion, the findings of this study provide a scientific foundation for future evaluation of the quality, further research, and practical use of FF herbs. [ABSTRACT FROM AUTHOR]

A method for determining human epidermal growth factor (hEGF) in cosmetics was developed using solid-phase extraction with high-performance liquid chromatography – tandem mass spectrometry. The sample was extracted and purified by a mixed anionic solid-phase extraction column (MAX), and the eluent was passed through a nylon filter membrane into a polypropylene vial. The matrix-matched external standard method was used to quantify the analyte in multi-reaction monitoring mode. The analyte had an excellent peak shape within 11 min with a linear range from 5 to 80 ng/mL and a linear correlation coefficient (r) of 0.9995. The limit of detection and limit of quantification were 0.75 and 2.5 μg/kg, respectively. The recovery of the target was from 81.5% to 88.8%, and the relative standard deviation was between 1.16% and 5.07%. The results met the International Organization for Standardization 12787 standard. The established method was successfully applied to 30 cosmetic samples. The proposed method is sensitive, accurate, reliable, and suitable for the quantitative confirmation of hEGF and monitoring its illegal addition to cosmetics. [ABSTRACT FROM AUTHOR]

AbstractCalyx of Diospyros kaki Thunb. (DKC), a famous traditional Chinese medicine, has a remarkable therapeutic effect on hiccups but its quality control is insufficient. In the study, a method was established by ultra-high performance liquid chromatography – mass spectrometry (UHPLC-MS). 17 peaks were observed in the mass spectrum and their chemical structures were preliminarily identified, including 3 organic acids and 14 flavonoids. The reference UHPLC fingerprint was built based on 25 batches of DKC samples, containing 15 common peaks. 11 batches of DKC samples from Guangxi and Hebei were superior to other 14 batches, sharing high similarity from 0.966 to 0.988 with the reference fingerprint. The chemometric methods, including hierarchical clustering analysis (HCA), principal component analysis (PCA), and partial least squares discriminant analysis (PLS-DA), were used to distinguish the DKC samples. The recognition methods clearly distinguished the medicinal materials from different regions, indicating that the main chemical constituents leading to the differences were protocatechuic acid, 4-hydroxybenzoic acid, rutin (presumptive result based on MS data), isoquercitrin, kaempferol, and hyperoside. The established fingerprint method is simple, rapid, repeatable, and specific and provides a reference for the quality evaluation of DKC. [ABSTRACT FROM AUTHOR]

The residues of xylazine and its metabolite in foods of animal origin are dangerous to consumers, but there has been no enzyme-linked immunosorbent assay (ELISA) or ELISA-like method reported to determine them so far. In this study, molecularly imprinted microspheres with xylazine as the template were synthesized, and 2,6-dimethylaniline (the metabolite of xylazine) was used as a hapten to prepare a streptavidinated horseradish peroxidase-labeled conjugate. A direct competitive pseudo-ELISA was developed on a microplate for xylazine and 2,6-dimethylaniline in milk. Because biotinylated horseradish peroxidase was employed to enhance the signal, the limits of detection for xylazine (0.003 ng/mL) and 2,6-dimethylaniline (0.005 ng/mL) were increased by 16.7- and 14-fold, respectively, compared to a horseradish peroxidase-labeled conjugate. Moreover, this material may be reused three times. The analysis of milk samples was consistent with values obtained by liquid chromatography tandem mass spectrometry. This is the first paper reporting a molecularly imprinted polymer-based method for the determination of xylazine and its metabolites in food. [ABSTRACT FROM AUTHOR]

A simple method for the determination of 19 types of phthalate acid ester plasticizers in raw textile solid waste has been developed by employing ultrasonic extraction coupled with gas chromatography – tandem mass spectrometry (GC-MS/MS). The evaluation of the plasticizers in several textile solid wastes showed that the levels were high, especially dimethylglycol phthalate. The extraction solvent, ultrasonic time, and ultrasonic temperature were optimized. Hexane was adopted as the extraction solvent, and ultrasonic extraction was performed at 20 °C for 30 min. A linear relationship from 0.02 to 1000 ng/mL was obtained with correlation coefficients(r) greater than 0.996. The limits of quantitation were from 0.08 to 30.70 µg/L based upon a signal-to-noise ratio (S/N) of 10. The recoveries were from 90.1% to 108.9% and the relative standard deviation between 0.78% and 9.43%. The method can be used for rapid screening and quantitative analysis of textile solid waste due to the simple, sensitive, and accurate assay. [ABSTRACT FROM AUTHOR]

A urea-based covalent organic polymer (UCOP), was synthesized using 1,4-phenylene diisocyanate (PPDI) and 4,4′,4″-(1,3,5-triazine-2,4,6-triyl) trianiline (TTTA) and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and nitrogen adsorption-desorption isotherm analysis. The prepared material was employed as an adsorbent for pipette tip–solid-phase extraction (PT–SPE) for benzimidazoles before high-performance liquid chromatography–tandem mass spectrometry analysis (HPLC–MS). The parameters affecting the isolation efficiency, including salt concentration, sample pH, mass of adsorbent, and types and volumes of eluent, were optimized. Using these conditions, PT–SPE provided good linearity from 0.1 to 10 μg kg−1 with low limits of detections (LODs) of 0.02 μg kg−1 together with good precision (relative standard deviations from 4.2 to 8.3%) and accuracy (recoveries from 76.2 to 84.8%). The results demonstrate that the urea-based covalent organic polymer has the potential for the enrichment of trace benzimidazoles. [ABSTRACT FROM AUTHOR]

A supramolecular solvent (SUPRAS)-based sample preparation method was proposed for the determination of lignans in Schisandra chinensis (S. chinensis) fruit. The optimal conditions were: proportion of hexafluoroisopropanol in SUPRAS: 35% (v/v), solid-to-liquid ratio: 20:1 mg/mL, and vortex time: 30 s. Additionally, simple, rapid, and sensitive high-performance liquid chromatography coupled with triple quadrupole mass spectrometry and multiple reaction monitoring was employed to simultaneously quantify seven lignans in S. chinensis. The validation showed that the linearity from 0.01 to 20.83 µg/mL was excellent (all R2 ≥ 0.99). The lowest limits of quantification were from 0.14 to 17.79 ng/mL. The relative standard deviation (RSD) of the intra-day retention time and peak area were from 0.12% to 0.21% and 2.35% to 6.41%. The RSD of retention time and peak area for the inter-day precision ranged from 0.17% to 0.32% and 3.83% to 7.39%. The average recoveries (80.21%–114.53%) demonstrated good accuracy for all analytes. The developed procedure was employed to determine lignans in processed and raw S. chinensis fruit. The lignans were concentrated in the seeds and the wine-processed material had the highest content. This study provides a reference for the analysis of S. chinensis fruit for lignans. [ABSTRACT FROM AUTHOR]

A coffee-certified reference material (CRM) for ochratoxin A, B, and C (OTA, OTB, and OTC) was created to improve the precision and reliability of these toxins. A collection of 100 bottles (each containing 10 g) of the CRM candidate for OTA, OTB, and OTC was produced by applying a mixed standard solution of OTA, OTB, and OTC to moderately roasted beans that subsequently ground and homogenized. Moreover, considering the intricate matrix interference in coffee, a rapid and sensitive method for OTA, OTB, and OTC in coffee was developed with minimal matrix effects. This approach employed liquid chromatography–tandem mass spectrometry and mixed purification materials (C18 and hydroxylated multi-walled carbon nanotubes (MWCNTs), OH-MWCNTs) for the analysis. Based on the standards GB/T 15000.3-2008/ISO Guide 35: 2017, the CRM demonstrated robust uniformity and stability when stored for 14 d at 4, 20, and 40 °C, and 12 months at −20 °C. Eight laboratories were employed to characterize the CRM. The certified values for OTA, OTB, and OTC in coffee were established to be 15.2 ± 0.4, 12.8 ± 0.4, and 3.4 ± 0.1 μg/kg (with a coverage factor k = 2, representing an approximate 95% confidence interval). [ABSTRACT FROM AUTHOR]

Glutathione (GSH)-switched fluorescent assays have received attention due to their rapid signal changes of fluorescent nanoprobes. Small polydopamine nanodots (PDs) exhibit remarkable photoluminescent properties. In this work, fluorescent PDs were synthesized through oxidation using dopamine as precursor. The prepared PDs had rich surface functionalities and exhibited good optical properties with maximum emission using 330 nm excitation. The fluorescence was quenched by Ag+ through the interaction with catechols in the PDs. After the addition of GSH, Ag was bound with sulfhydryl groups in GSH and the fluorescence of the PDs was restored. Therefore, a fluorescence turn on-off-on strategy was constructed for Ag+ and GSH using the synthesized PDs as the probe. The PDs showed good performance for Ag+ from 0.01 to 1 μM, with a limit of detection (LOD) equal to 2.82 nM. The system also exhibited a linear relationship for GSH from 0.01 to 0.5 μM with a LOD equal to 1.93 nM. GSH was determined in human serum to demonstrate a practical application of the assay. This work expands the application of PDs in biological analysis. [ABSTRACT FROM AUTHOR]

The development of polysaccharide drugs requires a thorough understanding of their quantitative and pharmacokinetic properties. However, the complexity of biological samples presents a challenge for direct analysis using UHPLC-QTOF MS. Therefore, it is essential to establish a method for the selective enrichment of polysaccharides. In this study, we developed an efficient method for the quantitative determination of polysaccharides by integrating magnetic molecularly imprinted polymers (MIPs) for sample pretreatment and UHPLC-QTOF MS for analysis. The MIPs were prepared using molecularly imprinted and boric acid affinity technologies, which combined the advantages of specific recognition and reversible binding to polysaccharides. The MIPs exhibited high dispersibility and uniform particle size, and adsorption experiments demonstrated their specific recognition of BG136, a polysaccharide with immunological activity. The proposed method was used for the purification and enrichment of BG136 in plasma with recoveries between 91.29% and 113.03%. This simple method demonstrated high selectivity, fast separation, and satisfactory recoveries providing an approach for polysaccharide determination with UHPLC-QTOF MS. [ABSTRACT FROM AUTHOR]

A promising and reusable nanohybrid based on carbon quantum dots immobilized with Fe3O4/zeolitic imidazolate framework-71/polypyrrole (CQD/Fe3O4/ZIF-71/PPy) was fabricated as a sorbent for ultrasound-and magnetic-assisted dispersive micro-solid-phase extraction (US-M-A-DMSPE) followed by high-performance liquid chromatography with ultraviolet detection (HPLC-UV) for simultaneous trace determination of cefixime (CFX) and cefdinir (CFD) in human plasma. In order to improve the contact between the analyte and the sorbent, the surface of the CQDs was modified by individual materials involving zeolitic imidazolate framework and polypyrrole via an in-situ synthesis of ZIF-71 followed by oxidative polymerization of pyrrole. The structure of the prepared sorbent was characterized by x-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Under the optimized conditions, the nanosorbent provided high adsorption and selectivity toward the analytes. The limits of detection for CFX and CFD were 0.15 and 0.04 ng mL−1, respectively. The coefficients of determination (r2) were between 0.990 and 0.993, with dynamic ranges of 0.5–1750.0 and 0.2–1500.0 ng mL−1. The method was used for quantifying CFX and CFD in plasma samples to evaluate the pharmacokinetic aspects, including the half-life (T½), the time to reach the maximum concentration (Tmax), the maximum plasma concentration (Cmax), area under the curve (AUC0-24) and area under the curve at infinite time (AUC0-∞). Reliable reproducibility as the intra- assay (≤ 6.3%) and inter-assay (≤ 8.7%) together with reasonable accuracy (≤ 8.8%) were obtained. [ABSTRACT FROM AUTHOR]

Per- and poly-fluoroalkyl substances (PFAS) are a large group of man-made chemicals that repel oil, stains, grease, and water and are fire resistant. PFAS are known to be persistent in the environment and bioaccumulate in human and animal tissue, soil, and water. To mitigate human exposure to these chemicals, PFAS analysis by ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) was used to monitor their presence in the environment. This study focused on analyzing oysters harvested from coastal New England for 14 PFAS. The validated method addressed in this study utilized a quick, easy, cheap, effective, rugged, and safe (QuEChERS) approach using various sorbents and showed that the combination of primary secondary amine/graphitized carbon black (PSA/GCB) provided the most effective sample clean-up prior to analysis. The recoveries for the targeted analysis ranged from 61% to 116.3% with relative standard deviations from 2.4% to 13.3% at the 125.0 ng mL−1 analyte level. The method detection limits were from 0.33 ng g−1 to 6.75 ng g−1. In a targeted analysis of five unknown samples, two samples had a detectable level of the legacy compound, perfluorooctanesulfonic acid (PFOS). [ABSTRACT FROM AUTHOR]

A rapid, sensitive, and reliable method based on ultrasound- assisted dispersive liquid–liquid microextraction followed by ion mobility spectrometry analysis (UA-DLLME-IMS) is reported for the preconcentration and determination of chlorpyrifos and dimethoate in food and water. The sample pH, volume of dichloromethane (extraction solvent), sonication, and centrifuge time, salt effect and sample volume were individually optimized. Under the optimum conditions, the calibration curves were linear from 5 to 200 µg L−1 and 3 to 280 µg L−1. Limits of detection (LOD) of 1.3 and 0.8 µg L−1 were obtained for chlorpyrifos and dimethoate, respectively. The relative standard deviations at 20 μg L−1 (n = 5) for intra- and inter-day precision were 2.8% and 3.9% for chlorpyrifos and 4.1% and 4.6% for dimethoate, respectively. The procedure was validated for the determination of chlorpyrifos and dimethoate in food and water samples. [ABSTRACT FROM AUTHOR]

Nonylphenols (NPs) are a degradation product of nonylphenol ethoxylate surfactants, which occur in many samples from the environment, food, and human organism. NPs are persistent and toxic and exhibit estrogenic activity. One of the challenges in understanding the estrogenic effects of NPs is the large number of isomers that may exist in different samples. After analyzing selected foods from different countries by high-performance liquid chromatography coupled with tandem mass spectrometry, NPs were detected in 8 of the 12 food samples. The concentration of NPs, based on fresh weight, ranged from 0.5 to 18.9 μg kg−1. The highest NP contents were found in coffee samples, and therefore an isomer-specific analysis was carried out by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GCxGC-TOF-MS). Fourteen pure isomers of NP were used as standards for cross-referencing the NP isomers. We identified the two main NP isomers in the coffee samples as 4-[3-ethyl-1,1-dimethylpentyl]-phenol and 4-[1-ethyl-1,3-dimethylpentyl]-phenol or NP128 and NP111 (Juelich nomenclature), respectively. The GCxGC-TOF-MS system with a liquid nitrogen cryogenic modulator used in this study is suitable for the isomer-specific analysis of NP and can be applied and further optimized for future routine analysis in food control. [ABSTRACT FROM AUTHOR]

Bamboo and wood are widely used as food contact materials (FCMs). Fungicides are often applied during the manufacture of these products to prevent mildew; thus, monitoring for fungicide residues is essential because of the possible risks to food safety. However, it is not clear whether residual fungicides in treated bamboo and wood products migrate into food to cause harm to humans, and there is an absence of procedures for these analyses. In this study, the simultaneous determination of fungicides was validated in bamboo and wood FCMs by high-performance liquid chromatography–triple quadrupole tandem mass spectrometry (HPLC–MS/MS). The analytes were extracted with methanol or 1:1 methanol/acetonitrile and purified using 25 mg primary secondary amine adsorbent with 2.5 mg graphitized carbon black or 25 mg PSA with 25 mg octadecylsilane (C18). The recoveries for wood and bamboo FCMs were from 60.0% to 100.7% and 70.0% to 97.5%, respectively. The intra-day precision of wood and bamboo FCMs were from 0.1% to 5.3% and 0.1 to 3.0%, and the inter-day precision from 0.3% to 8.5% and 1.2% to 7.8%, respectively. The limits of detection ranged from 0.11 to 15.38 for wood and 0.25–6.19 μg kg−1 for bamboo. This method provides a reference for the determination of fungicides in bamboo and wood FCMs. [ABSTRACT FROM AUTHOR]

A paper spray tandem mass spectrometric (PS-MS/MS) method without column separation was developed for the rapid screening of clonidine in dietary supplements. PS-MS/MS provided acceptable performance compared to high-performance liquid chromatography – tandem mass spectrometry (HPLC-MS/MS) in terms of limits of detection and quantification, accuracy, and precision. To overcome ionization suppression of complicated plant-based pharmaceutical products, nizatidine, tizanidine, and apraclonidine were investigated as internal standards. A more similar structured internal standard is most suitable for matrix effect compensation. The developed method has advantages of simplicity and speed for the screening of clonidine in dietary supplements. [ABSTRACT FROM AUTHOR]

A new magnetic graphene oxide (MGO) composite was developed as an adsorbent for the preconcentration of lenalidomide (LND) by ultrasound-assisted solid-phase extraction (UA-SPE) prior to determination by high-performance liquid chromatography with ultraviolet detection (HPLC-UV). The adsorbent was fabricated through chemical functionalization of a new surface-active ionic liquid (SAIL), i.e. 1-methyl-3-(trimethoxysilyl propyl)-imidazolium dodecyl sulfate (TMES-Im-DS) on MGO. The synthesized material presented the benefits of excellent adsorption for LND. The characterization of the synthesized functionalized magnetic nanocomposite was performed by Fourier transform-infrared spectroscopy, field emission scanning electron microscopy, Brunauer–Emmett–Teller (BET), vibrating sample magnetometry, and energy-dispersive X-ray spectroscopy. After optimization of the parameters, the limits of detection (LOD) and limit of quantification (LOQ) were 0.2 and 0.8 µg L−1 and 0.6 and 2.5 µg L−1in water and plasma samples, respectively. The enrichment factors (EFs) were from 90 to 180 in the samples. The relative standard deviation (RSD%, n = 5) as intra- and inter-day precision were from 6.3% to 7.5% and 7.1% to 8.5% in water and plasma, respectively. Lastly, the developed method presented good results for the preconcentration of LND in plasma with satisfactory repeatability. [ABSTRACT FROM AUTHOR]

A method is reported for the simultaneous determination of ceftazidime and avibactam in human plasma and cerebrospinal fluid utilizing high-performance liquid chromatography – tandem mass spectrometry (HPLC-MS/MS). The validated method was used to monitor the drugs in the treatment of central nervous system infections. The analytes were extracted from plasma and cerebrospinal fluid by simple protein precipitation using acetonitrile. A reversed-phase HSS T3 column (5.0 μm, 4.6 × 100 mm, Waters) was employed for the separation with a total analysis time of 5 minutes. Ceftazidime and avibactam eluted in 2.15 min and 2.87 min, respectively. The acquisition was separated into two periods to allow analysis in different ionization modes. A multi-reaction monitoring analysis was performed with the transition m/z 547.2–468.1 for ceftazidime, and m/z 552.3–468.1 for ceftazidime-d5 (positive mode), m/z 263.9–96.1 for avibactam, and m/z 136.8–92.8 for salicylic acid (negative mode). The plasma calibration curves of the analytes displayed good linearity across the range from 1 to 100 μg/mL for ceftazidime and 0.1–20 μg/mL for avibactam. Calibration curves for cerebrospinal fluid assay were established from 0.4 to 16 μg/mL (ceftazidime) and 0.2–8 μg/mL (avibactam). The accuracy was between 89.5% and 108.5%. The within- and between-batch precisions with the relative standard deviation were lower than 15%. The developed method had no observed matrix effects. The analytes were stable during the analytical and sample processing. The developed and validated method was successfully applied in routine clinical practice and helps to assess the adequacy of therapy and ensure sufficient ceftazidime and avibactam levels in central nervous system infections. [ABSTRACT FROM AUTHOR]

Plastic recycling is necessary to reduce pollution. However, the impurities in recycled plastics restrict their applications. Potential contaminants in recycled plastics were investigated by untargeted and targeted liquid chromatography-mass spectrometry (LC-MS). More than 2000 features were screened by comparing the recycled plastics with food contact polyolefin materials. A total of 126 substances was identified using the mzCloud database. In order to assess the risk of recycled plastics, Cramer rules were applied to predict the safety levels of the identified compounds. 23 identified Cramer class III compounds were assigned, including plasticizers, antioxidants, and flame retardants. Six more commonly identified toxic compounds were further characterized by standards using tandem mass spectrometry. These results suggested that the identification of contaminants in recycled plastics by LC-MS and mzCloud match was reliable. Additionally, their concentrations were determined by LC-MS to estimate the potential risk of recycled plastics. The results show that the organic additives in recycled plastics and food contact polyolefins are significantly different. Recycled plastics may present a safety risk and should be assessed before use in some applications. [ABSTRACT FROM AUTHOR]

Liquid chromatography – tandem mass spectrometry (LC-MS/MS) is routinely applied for the determination of toxins associated with diarrhetic shellfish poisoning (DSP) as a part of the Japanese official method. For scallops, not only the edible part but also the midgut gland may be used for analysis. In this study, the matrix effects in the LC-MS/MS-based determination of okadaic acid (OA) and dinophysistoxin-1 (DTX1) in the scallop midgut gland were evaluated to assess the impact on the accuracy of the results. The analyzed sample in an interlaboratory comparison study was subjected to the Japanese official method. The solutions obtained with and without a cleanup process (combination of hexane washing and solid-phase extraction using a C18 cartridge) were diluted to varying ratios and used for evaluation. For all prepared solutions, the ionization of OA and DTX1 was enhanced compared to the samples in methanol; the cleanup process did not sufficiently reduce the matrix effects. Although the dilution of the sample solution reduced the matrix effect, the improvement was limited. Another pretreatment technique is necessary for the accurate determination of DSP-associated toxins in this matrix. [ABSTRACT FROM AUTHOR]

Alpha-methylthiofentanyl and thiofentanyl are psychoactive substances that have been abused in recent years, strongly threatening social and public security. Because they are rapidly metabolized in vivo, their determination presents a great challenge for forensic science. An automated method of online solid-phase extraction coupled with ultra-high performance liquid chromatography—tandem mass spectrometry was developed for the determination of alpha-methylthiofentanyl, thiofentanyl, and the metabolite norfentanyl in urine. The analytes were first enriched and purified by an Oasis HLB online SPE column and eluted on a Hypersil GOLD C18 analytical column. Chromatographic separation was achieved with mobile phase components of 2 mM ammonium formate and 0.1% formic acid in water and same composition in methanol in gradient elution mode. The limit of detection and lower limit of quantitation of the method for the three analytes were 0.2 and 2 pg/ml, respectively. Acceptable linearity was obtained from 2 to 800 pg/ml. The accuracy was in the range of 87.98–108.95%; and precision, calculated as the relative standard deviation, was less than 14.63%. The method recoveries were from 65.56 to 113.72%. This highly sensitive method was applied to study the detection window of the precursor compounds and metabolites in rat urine. Both alpha-methylthiofentanyl and thiofentanyl are metabolized to norfentanyl, which was first revealed in this study. With the aid of norfentanyl, the detection windows of alpha-methylthiofentanyl and thiofentanyl were extended to 18–26 days and 20–27 days, respectively. This study provides important auxiliary tools for the forensic identification of fentanyl analogs. [ABSTRACT FROM AUTHOR]

Cephalexin (CFE) residues in animal-derived food and its deleterious effects on human health has attracted extensive attention. In this study, a specific anti-cephalexin monoclonal antibody (mAb) was used to develop an indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) with a half-maximal inhibitory concentration (IC50) of 1.83 µg/L that was suitable for the determination of cephalexin in animal-derived foods. The limit of detection (LOD) and limit of quantitation (LOQ) for cephalexin were from 0.44 to 0.58 µg/kg and 0.57 to 0.67 µg/kg, respectively. The recovery was from 90.1 to 103.6% with coefficients of variation (CV) less than 10.0%. In addition, the established ELISA method and high-performance liquid chromatography – mass spectrometry (HPLC-MS/MS) were used to analyze the samples with good correlation between the results. The results show that the established ic-ELISA is suitable for the determination of cephalexin in animal-derived food. [ABSTRACT FROM AUTHOR]

Bidirectional effects between parasite and its hosts are important because the chemical differences of parasite produced by host may affect its medicinal properties. In this study, the chemical variations between Viscum coloratum, a traditional Chinese medicine (Hujisheng in Chinese, HJS), and its host were explored using metabolomics based on ultra-high performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC/Q-TOF-MS). The characterization of Hujisheng was performed for the subsequent chemical interaction study. Fifty-five compounds were identified including twenty-nine flavonoid glycosides (FGs), eight linear diphenyheptanes (LDHs), eight phenolic acids, and ten other compounds. Eleven novel flavonoid glycosides were screened and putatively characterized using six-point mass defect filtering (MDF). Significant chemical differences in Hujisheng caused by the host were discovered by metabolomics and multiple chemometric methods. In addition, the haustorium of Hujisheng was isolated from its host and analyzed by UPLC/Q-TOF-MS. Upon the comparative analysis of Hujisheng, the haustorium, and the hosts, differential chemical compounds were ascribed to host diversity and are believed to be transmitted between the parasite and host through the haustorium. [ABSTRACT FROM AUTHOR]

Heterocyclic aromatic amines (HAAs) are carcinogenic and mutagenic compounds formed by the cooking of meat and combustion of biomass. There are relatively few data on HAAs in atmospheric particulate matter (PM). We developed an analytical method using high performance liquid chromatography – tandem mass spectrometry (tandem quadrupole, HPLC-MS/MS(QqQ)) to analyze PM samples for 12 HAAs. We applied this method to an urban air standard reference material and wildfire-impacted PM2.5 from the 2018 wildfire season in Northern California. The PM sample matrix adversely impacted the MS/MS response, with high levels of ion suppression for sample masses >4 mg and higher ion suppression in wildfire-impacted particulate matter compared with the standard reference material. Despite detection limits at the low ng level, no HAAs were detected in the standard reference material, but β-carboline norharman (0.34 ng/m3) was detected in one wildfire sample. [ABSTRACT FROM AUTHOR]

Per- and poly-fluoroalkyl substances (PFASs) are a class of synthetic organic chemicals that include thousands of compounds. Analytical methods for PFASs in vegetables are limited. In this study, a rapid and sensitive method using on-line solid phase extraction (SPE) coupled with ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed and validated for the simultaneous determination of 21 PFASs in vegetables. The extraction solvent volume and procedure were optimized to achieve good efficiencies (>93%) using the lowest quantity of solvent. The injection volume, elution condition of the online SPE system, and the mobile phases of the UHPLC-MS/MS system were also optimized to improve the sensitivity, peak symmetry, and resolution. The method detection limits of the 21 targeted PFAS were from 0.001 to 0.008 ng/g and the linearity was from 0.1 to 1000 pg/mL using an injection volume of 5 mL. The validation results indicate that this method is precise, accurate, and robust. Moreover, this method is high throughput (∼15 min per sample); thus, suitable for analyzing a large number of vegetable samples in a short time interval. In addition, the developed method was successfully applied to analyze vegetables. The results show that the total PFAS concentrations were the highest in lettuce, followed by potatoes and tomatoes, and the lowest in broccoli. Different profiles of PFASs were observed among the vegetable species. [ABSTRACT FROM AUTHOR]

Trapa natans L., also known as water chestnut, is a medicinal plant that contains a high quantity of phenolic compounds. Traditionally the plant has been used for several important medicinal purposes. The goal of the present study is to validate a HPLC method to quantify phenolic compounds from the roots, leaves, kernel, and shell fruit of Trapa natans L. A high-performance liquid chromatography-diode-array detection method has been developed for the simultaneous separation and identification of seven phenolic compounds. Rapid HPLC separation was achieved using a C18 column with a mobile phase gradient of 0.1% acetic acid and acetonitrile. The method was validated for linearity, specificity, precision, and accuracy. The developed method was suitable to quantify seven phenolic compounds in extracts obtained by different protocols. The Soxhlet extraction provided the highest content of phenolic compounds. [ABSTRACT FROM AUTHOR]

Phenolic benzotriazoles are used as ultraviolet stabilizers in consumer products and have been detected in the environment suggesting potential human exposure. Phenolic benzotriazoles were nominated to the Division of National Toxicology Program for testing based on their potential widespread human exposure and lack of adequate toxicity data. Nine chemicals were selected for toxicological evaluation, representing unsubstituted (2-(2H-benzotriazole-2-yl)phenol, (P-BZT)), monosubstituted (drometrizole; 2-(2H-benzotriazol-2-yl)-4-tert-butylphenol (tBu-BZT); octrizole), disubstituted (2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (diMeEtPh-BZT), 2-(2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylpropyl)phenol (ditPe-BZT); 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxybenzenepropanoic acid, octylester (tBuPrOcEst-BZT) and halogenated trisubstituted (bumetrizole; 2-(5-chloro-2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylethyl)phenol (ditBuCl-BZT)) compounds. Different extraction methods were utilized and methods were developed to determine phenolic benzotriazoles by quantitating free (unconjugated parent) and total (free and conjugated parent) analytes in plasma of rats to aid in interpretation of toxicity data, understanding of absorption, distribution, metabolism, and excretion differences. The calibration standard range was from 1 to 500 ng/mL for free analytes and 1 to 1000 ng/mL for total analytes. The methods were linear (r2 ≥ 0.99). The accuracy was determined as the relative error (RE) and ranged from −18.2 to +17.8, and precision as the relative standard deviation (RSD) and ranged from 0.0 to 20.1% for both free and total plasma calibration standards, respectively. The limits of quantitation were ≤5.0 and 10.0 ng/mL and limit of detection ≤ 1.2 and 2.0 ng/mL, for free and total analytes, respectively. These results demonstrate that the methods are suitable for quantitation of free and total analytes in rat plasma. [ABSTRACT FROM AUTHOR]

The indiscriminate use of organophosphorus pesticides poses a great threat to human health because of harmful substance bioaccumulation. We developed a rapid and reliable method for the simultaneous determination of chlorpyrifos, isocarbophos, methamidophos, omethoate, and triazophos in procine hair. The targets were separated by a C18 column (2.1 × 100 mm, 1.8 µm) and analyzed by electrospray ionization using the positive mode of a triple quadrupole mass spectrometer. The analytes had linear relationships from 1.0 to 100 µg/kg. The correlation coefficients were all greater than 0.998. The limits of detection ranged from 0.4 to 0.9 µg/kg, and the limits of quantification from 1.2 to 2.0 µg/kg. The recoveries were from 76.1% to 106.2%. The intra-assay and inter-assay precision rates were from 1.6% to 4.4% and 2.3% to 6.9%, respectively. The intra-day and inter-day accuracy ranged from 2.5% to 9.3% and 3.2% to 8.9%, respectively. This method was a valid tool to monitor organophosphorus pesticides in breeding and livestock products. [ABSTRACT FROM AUTHOR]

To date, many analogies of sildenafil, tadarafil, and vadenafil, which are phosphodiesterase-5 (PDE5) inhibitor have been reported. On the other hand, a novel type of PDE5 inhibitor, thioquinapiperifil has not yet been evaluated. Therefore, in this study, liquid chromatography quadrupole time of flight mass spectrometry (LC-Q-TOF-MS) was conducted to determine the in vitro and in vivo metabolites of thioquinapiperifil. Metabolites in urine and feces samples of rats injected with thioquinapiperifil and in human liver microsomal extract were characterized to examine its possible metabolic pathways. Metabolized samples were extracted and precipitated using acetonitrile and subsequently injected into the LC-Q-TOF-MS system. Peaks of interest were analyzed via tandem-mass spectrometry to identify the metabolite structure. A total of 11, 5, and 7 metabolites were detected in human liver microsomal extract, rat urine, and rat feces, respectively. The mass error values of all TOF mass results were within 5 ppm, indicating high accuracy. These newly identified metabolites may be useful for evaluating the toxicology of thioquinapiperifil and this knowledge may be applied to related forensic cases. [ABSTRACT FROM AUTHOR]

A sensitive and efficient magnetic amino modified multi-walled carbon nanotubes (m-MWCNT-NH2)-based magnetic dispersive solid-phase extraction (m-dSPE) coupled with hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC-MS/MS) strategy is reported for the simultaneous determination of 13 paralytic shellfish toxins (PSTs) in bivalve mollusks. The samples were extracted twice with 1% acetic acid and purified using optimized m-dSPE procedures with Fe3O4 coated MWCNT-NH2 composites as magnetic adsorbents. The adsorbed PSTs on the m-MWCNT-NH2 adsorbents were separated using a Ni-coated neodymium magnet and subsequently eluted with 2 mL water–acetonitrile–acetic acid (80:20:1, v/v/v) and analyzed by HILIC-MS/MS. The correlation coefficients (r) of the targeted toxins obtained in matrix-matched external standard curves were from 0.997 to 0.999. The PSTs were acquired and quantified in the multiple reaction-monitoring mode and the limits of detection and quantitation in bivalve mollusks were 1.10 to 4.51 μg/kg and 3.67 to 13.5 μg/kg, respectively. Spiked recoveries at three concentrations in negative samples were from 73.4% to 92.5% with precision less than 10.6%. The method validation was in accordance with 2002/657/EC guidelines and method application in commercial bivalve mollusk samples. The developed method was rapid, convenient and economical for the determination of the targeted toxins. [ABSTRACT FROM AUTHOR]

Garcinia cambogia extract (GCE) is a popular botanical supplement used in weight loss products. Hydroxycitric acid (HCA) is the principal component in GCE. Due to lack of adequate toxicity data to assess the safe use of GCE, the National Toxicology Program is testing GCE in Hsd:Sprague Dawley SD rats following perinatal exposure and in adult B6C3F1/N mice. We report a validated method utilizing sample clean up with ultrafiltration followed by liquid chromatography—tandem mass spectrometry (LC-MS/MS) analysis to quantify HCA in rat plasma across the concentration range from 20 to 800 ng/mL. The method was linear (r2 ≥ 0.99) with limits of quantitation (LOQ) and detection (LOD) equal to 20.0 and 3.9 ng/mL plasma, respectively. The accuracy (determined as the relative error, RE) and precision (determined as the relative standard deviation, RSD) using quality control standards analyzed over multiple days were ≤ ± 7.5% and ≤9.5%, respectively. The method was applied to quantify HCA in study matrices (relative error ≤ ± 23.0%; relative standard deviation ≤ 6.0) except gestational day (GD)18 fetus. The method was partially validated in GD18 fetal homogenate across the concentration range from 60 to 3000 ng/g (r2 ≥ 0.99, relative error ≤ ± 11.9%, and relative standard deviation ≤ 5.5%; LOQ 60.0 ng/g; LOD 7.77 ng/g). Standards as high as 20,000 ng/mL (plasma) and 502,000 ng/g (fetus) were successfully quantified after dilution into the validated range (relative error ≤ ± 2.6%; relative standard deviation ≤ 5.2%). These results demonstrate that the method is suitable to quantify HCA in rodent matrices and may be adapted to other biological matrices. [ABSTRACT FROM AUTHOR]

The goal of the current work was to study the phytochemical content of Onosma inexspectata Teppner and O. armenum DC. The antioxidant properties using six assays and the enzyme inhibitory capacities against α-amylase, α-glucosidase, tyrosinase, and the anti-cholinesterase were also evaluated. The levels of phenolic compounds were approximately 22 and 28 mg gallic acid equivalent/g for O. inexspectata and O. armenum, respectively. Twenty-seven compounds were identified and quantified using liquid chromatography–electrospray ionization tandem mass spectrometry. Chlorogenic acid, apigenin 7-glucoside, and luteolin 7-glucoside were the major compounds in O. inexspectata. Onosma armenum contained an attractive level of hesperidin. The antioxidant assays showed significant differences between the two species, except for the phosphomolybdenum assay. The results of the inhibitory enzyme assays revealed no significant differences between the extracts, except for α-glucosidase inhibition. The present study may underline the possibility to use O. inexspectata and O. armenum as promising sources of phytochemicals that may serve against many body disorders. [ABSTRACT FROM AUTHOR]

Thermogravimetric methods with internal polymer standards have successfully quantified environmental tire and road wear particle (TRWP) concentrations. However, TRWP quantification in environmental matrices via pyrolysis-gas chromatography-mass spectrometry (py-GC-MS) using butadiene rubber (BR) and styrene-butadiene rubber (SBR) marker 4-vinylcyclohexene (4-VCH; 1,4-butadiene-1,4-butadiene dimer) may be uncertain because of variable polymer compositions and BR and SBR microstructures. To determine if tire polymer microstructure is contributing to potentially over- or underestimating TRWP in the environment in py-GC-MS analyses, SBR materials (n = 8) commonly found in tire tread with varying microstructure were quantified via py-GC-MS, using 4-VCH and the deuterated internal standard d-4-VCH to provide a response ratio for each polymer. The response ratios of the dimer response to the total polymer quantity (instrument response slope) varied up to 6.8-fold for SBR, with a reduction to a 3.6-fold range when the polymer quantity was expressed as 1,4-butadiene mass rather than total polymer mass. Variability was reduced further when considering the polymerization method for emulsion-SBRs (n = 3; 1.4-fold range), but not solution-SBRs (n = 5; 2.7-fold range), which reflects the random versus structured heterosequencing of the two rubber types, respectively. Our findings suggest that py-GC-MS response should be interpreted based on empirical analysis of an appropriate number of regionally representative tire tread materials, rather than individual rubbers, because of the lack of methods available for determining unknown average microstructure in environmental samples. [ABSTRACT FROM AUTHOR]

Many environmental chemicals are known to disrupt thyroid function. Measurement of thyroid hormones in animal studies provides useful information to understand the effects of environmental chemicals on thyroid hormone metabolism. We report an efficient method, utilizing a protein precipitation followed by ultraperformance liquid chromatography-tandem mass spectrometry analysis, to quantitate total 3,3',5-triiodo-L-thyronine (triiodothyronine, T3) and total 3,3',5,5'-tetraiodo-L-thyronine (thyroxine, T4) in rodent serum. The use of synthetic serum for calibration standards eliminated the interferences from endogenous total T3 and T4 and allowed the experimental lower limits of quantitation (LOQ) to be set at the required concentration (T3, 20 ng/dL; T4, 0.5 µg/dL) to allow quantitation of endogenous concentrations. The method was linear (r > 0.99; range 20.0-600 ng/dL T3, 0.500-15 µg/dL T4) with good assay recoveries (90.4-107%) for both analytes. Intra- and inter-day accuracy, estimated as percent relative error, were ≤ ±7.6% and intra- and inter-day precision, estimated as the relative standard deviation, were ≤ 5.3% for both analytes. The method may easily be adapted to a well-plate format thereby further improving the efficiency. Total T3 and T4 concentrations were stable in male and female rat and mouse serum when stored in the freezer (∼−70 °C) for up to 62 d with determined values within 92.8-111% of day 0 for both analytes. The method can be extended to quantitate total T3 and T4 concentrations in humans or other species with minimal optimization. [ABSTRACT FROM AUTHOR]

An amino-modified multiwalled carbon nanotube (MWCNT) solid-phase extraction-based hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC–MS/MS) method was developed for simultaneous determination of 13 paralytic shellfish toxins (PSTs) in bivalve mollusks. Shellfish samples were extracted with 1% acetic acid followed by cleanup using optimized MWCNT-NH2 based solid-phase extraction. Absorbed PSTs were eluted with 2 mL 1% acetic acid–acetonitrile (70/30, v/v). The separation was performed on a Waters BEH Amide column within 7.5 min utilizing 0.1% formic acid–acetonitrile and 2 mM ammonium acetate containing 0.1% formic acid as the mobile phase. The analytes were quantified by matrix-matched external standard curves with correlation coefficients® exceeding 0.997 acquired in multiple reaction-monitoring mode. The limits of detection and quantitation in shellfish samples were from 2.76 to 9.8 μg/kg and 9.11 to 39.3 μg/kg, respectively. Recoveries at three spiked levels ranged from 71.4% to 97.8% with relative standard deviations less than 12.6%. The developed method was satisfactorily applied to the analysis of shellfish. [ABSTRACT FROM AUTHOR]

High-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (HPLC/QTOF–MS) is reported for quantitative determination of pesticide residues in apples. After a simple, rapid extraction, 300 mg MgSO4, 50 mg primary secondary amine (PSA), and 250 mg octadecyl (C18) were used for sample clean-up to ensure efficient recovery. The pesticides were quantified by HPLC/QTOF–MS using high-resolution multiple reaction monitoring (HR-MRM). Matrix-matched external standard calibration was used for quantitative analysis. The developed method was validated by spiking blank samples with the analytes and provided satisfactory accuracy verified by recoveries from 78.9% to 109.4% and good precision (relative standard deviation ≤12.4%). The limits of quantification for all analytes were between 0.85 and 3.0 µg/kg. The method was successfully applied to the analysis of forty batches of real samples, demonstrating its effectiveness for routine application. [ABSTRACT FROM AUTHOR]

Aminoglycoside antibiotics exhibit broad-spectrum antibacterial activity, good efficacy, and stability. However, due to the emergence of antibiotic resistance, their use as broad-spectrum antibiotics is restricted. Bacteria producing the bifunctional enzyme, 6′-aminoglycoside acetyltransferase 2″-aminoglycoside phosphotransferase [AAC(6′)-APH(2″)], can modify aminoglycoside antibiotics, leading to the emergence of clinical drug resistance. A method based on ultra-high performance liquid chromatography–mass spectrometry (UHPLC-MS) is reported to monitor the modification of aminoglycoside antibiotics and to screen potential inhibitors of AAC(6′)-APH(2″) from marine natural products. Instead of using purified AAC(6′)-APH(2″), Escherichia coli cells harboring AAC(6′)-APH(2″) were employed. In vivo enzyme assays, conducted in the physiological environment, compensated for the disparity between in vitro responses and those in living cells. The inhibition zone method was used to verify the reliability of the UHPLC-MS results. From a library of 63 marine natural products, Mer-C-3 and Mer-c-8e pyridine alkaloids were shown to provide inhibitory activity against AAC(6′)-APH(2″) in living bacteria. The UHPLC-MS-based approach offers improved speed, convenience, and sensitivity compared with the traditional inhibition zone assay for the screening of enzyme inhibitors. [ABSTRACT FROM AUTHOR]

A rapid and sensitive method was developed determine free fatty acids in cyanobacteria extracellular medium without derivatization by stir bar sorptive extraction (SBSE) coupled to ultra-high-performance liquid chromatography – tandem mass spectrometry (UHPLC-MS/MS). The stir bars (20 mm in length and 1 mm in film thickness) coated with polydimethylsiloxane was used to directly extract 11 free fatty acids (C14-C24) in cyanobacteria extracellular media. The performance was optimized, including the column, temperature, extraction time, organic modifier, and desorption solvent. Limits of detection and quantification, precision, and linear dynamic ranges for the free fatty acids were evaluated. The method was applied to determine free fatty acids in cyanobacteria extracellular media at the exponential and plateau phases. Eicosanoic acid (C20:0), linoleic acid (C18:2), oleic acid (C18:1), stearic acid (C18:0), palmitic acid (C16:0) and myristic acid (C14:0) were quantified in the samples. [ABSTRACT FROM AUTHOR]

Parabens are widely used as antimicrobial preservatives in cosmetic products and pharmaceuticals. Therefore, their presence in the environment is considered to be serious and their determination is important. This paper reports the development and validation of a new method based on solid-phase microextraction (SPME) and high-performance liquid chromatography – tandem mass spectrometry (HPLC-MS/MS) for the simultaneous determination of five parabens (methylparaben (MP), ethylparaben (EP), propylparaben (PP), butylparaben (BP) and benzylparaben (BzP)) in surface water. The polymer sorbent was obtained by the electropolymerization of 3,4-ethylenedioxythiophene on a stainless steel spring support. The parameters affecting the extraction efficiency of parabens were optimized. Under optimal conditions, the extraction recoveries ranged from 88 to 98% except for BzP (70%). Good linear responses were obtained with correlation coefficients (r2) exceeding 0.999. The detection limits were from 0.004 to 0.28 µg L−1. The method was successfully applied for the determination of parabens in lake water. [ABSTRACT FROM AUTHOR]

In addition to currently used methods of gas chromatography with flame ionization detector or mass spectroscopy detection (GC–FID and GC–MS) for the analysis of seized heroin, a novel rapid high-performance liquid chromatography with tandem mass spectrometry (HPLC–MS/MS) method for detection and quantification of the main alkaloids was developed. This method for detection and quantification of heroin, papaverine, noscapine, and acetyl thebaol was validated and applied to analysis of seized heroin street samples. The method is rapid (6 min) and implies a low solvent consumption (0.75 mL min−1), suitable as an alternative method for GC–MS for heroin samples stored at elevated temperatures. The method was successfully tested on seized heroin samples. [ABSTRACT FROM AUTHOR]

An improved analytical method was developed for the simultaneous quantification of ionic and nonionic perfluoroalkyl substances (PFASs) in surface water followed by ultra-high performance liquid chromatography (UHPLC-MS/MS). The conditions for liquid chromatography and mass spectrometry were optimized and several solid phase extraction cartridges and elution solvents were compared. The low detection limits of the analytes ranged from 0.010 to 0.285 ng/L. Reasonable recoveries (76.4–112.3%) were demonstrated at different spiked levels with relative standard deviations lower than 18.9%. The method was applied for the surface water samples collected from different sampling sites in the Qiantang River, China. The results showed that 7 perfluoroalkyl carboxylic acids and 3 perfluroalkane sulfonic acids were detected while perfluorosulfonamide were not present. In addition, the total concentrations of PFASs in middle and downstream of the Qiantang River were higher (154.11–199.28 ng/L) than upstream (9.38–9.80 ng/L), which may be due to presence of the textile and paper industries. [ABSTRACT FROM AUTHOR]