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Herein, we developed a simple analytical procedure for the quantitation of bithionol residues in animal-derived food products such as porcine muscle, eggs, milk, eel, flatfish, and shrimp using a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction method coupled with liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI + /MS-MS). Samples were extracted with 0.1% solution of formic acid in acetonitrile and the extract was purified using a C18 sorbent. Separation was performed on a Waters XBridge™ C18 reversed-phase analytical column using 0.1% solution of formic acid/acetonitrile as the mobile phase. Six-point matrix-matched calibration indicated good linearity, with the calculated coefficients of determination (R 2 ) being≥0.9813. Intra- and inter-day recoveries (determined at spiking levels equivalent to 1×and 2×the limit of quantitation (0.25μg/kg)) ranged between 80.0 and 94.0%, with the corresponding relative standard deviations (RSDs) being≤8.2%. The developed experimental protocol was applied to different samples purchased from local markets in Seoul, which were tested negative for bithionol residues. In conclusion, the proposed method proved to be versatile and precise, being ideally suited for the routine detection of bithionol residues in animal-derived food products with various protein and fat contents., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction method coupled with liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI + /MS-MS) was developed for quantification of fenobucarb residues in animal food products, such as porcine muscle, egg, and whole milk, and aquatic food products, such as eel, flatfish, and shrimp. Acetonitrile with the addition of 0.1% trifluoroacetic acid was employed as an extraction solvent and was compared with acetonitrile alone and 0.1% formic acid in acetonitrile. All extracted samples were purified using C18 sorbent. The best extraction efficiencies, expressed as recovery at two spiking levels equivalent to 1- and 2-times the limit of quantification (LOQ=2μg/kg) were achieved using 0.1% trifluoroacetic acid in acetonitrile and ranged from 61.38 to 102.21% in all matrices, with relative standard deviations (RSDs) < 13% (except for the low spiking of porcine muscle and the high spiking of whole milk, for which the RSDs were>20%). Six-point matrix-matched calibration was used for quantification and the determination coefficients were good (R 2 ≥0.9865). The method was verified by application to samples purchased from local markets and none of the samples tested positive. In conclusion, the developed method is simple and versatile and can be used for the routine detection of fenobucarb in different animal food products having varying protein and fat contents with satisfactory accuracy and precision., (Copyright © 2017 Elsevier B.V. All rights reserved.)

An analytical method was developed to quantify the residual levels of the neonicotinoid insecticides, acetamiprid and thiacloprid, in field-incurred butterbur samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Samples were extracted with acetonitrile and partitioned with dichloromethane. After partitioning, purification was conducted using a Florisil ® cartridge. Linearity of a matrix-matched calibration curve of the two compounds over a concentration range of 0.004-0.4μg/g was excellent, with determination coefficients (R 2 )≥0.9998. The limits of detection (LOD) and quantitation (LOQ) for both acetamiprid and thiacloprid were 0.0006 and 0.002mg/kg, respectively. The average recoveries for acetamiprid and thiacloprid at two spiking levels (0.02 and 0.1mg/kg, i.e., 10×LOQ and 50×LOQ) were between 78.23 to 82.17%, with relative standard deviations (RSDs)≤7.22%. The method was successfully applied to field-incurred samples treated with a commercial pesticide product, either once (zero or 7 days before harvest) or twice (0 and 7, 7 and 14, or 14 and 21 days before harvest). The highest and lowest residues were obtained for the 7 and 0 days' treatment and the 21 and 14 days' treatment, respectively. The developed method is simple and accurate and can be extrapolated to other leafy vegetables., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The current study was undertaken to validate the performance for the determination of both TBA and beta-trenbolone (beta-TB) residues in porcine muscle at concentrations required to monitor compliance with the maximum residue limit (MRL). The method involves a one phase liquid-liquid extraction, cleanup with low-temperature fat precipitation, separation of the respective compounds by HPLC on a Capcell pak C(18) column, use of a methanol-water isocratic system as an eluent, and measurement by UV absorbance detection at 340 nm. Both compounds were confirmed using LC-MS/MS with electrospray interface (ESI) and a triple quadrupole (QqQ) analyzer. The method was found to be precise and accurate, with a linearity range of 1-10 microg/kg (r(2) >0.973). The intra- and interday precision showed good reproducibility with RSDs < or =13.25%. The LODs were 0.12 and 0.22 microg/kg, and the LOQs were 0.37 and 0.66 microg/kg, for TBA and beta-TB, respectively. The applicability of the method was demonstrated by analyzing real samples collected from major cities in the Republic of Korea. No residues of the selected compounds were detected in any of the samples. The advantages of our method are that it is: selective, sensitive, requires a short time for analysis (13 min), and performs simple sample extraction and clean-up procedure with low-temperature fat precipitation as compared to the previously published methods.

A simple and effective method was developed for analyzing dinotefuran and its three metabolites (MNG, UF, and DN) in plum using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Due to the polarity and high water miscibility, dinotefuran and some of its metabolites (especially DN) have some limitations to be extracted with acetonitrile and salt following the “QuEChERS” sample preparation methodology. Alternatively, the samples were extracted with methanol, and purified with dispersive-solid phase extraction procedure (d-SPE) using primary secondary amine (PSA) and C 18 sorbents after filtration, and mass up. Due to the suppression effect originated from plum matrix, matrix-matched calibration curves, which provided good linearity with coefficient of determination ( R 2 ) ≥ 0.998, were used for quantification of all analytes. Blank plum samples fortified with 2 spiking levels (10 × LOQ and 50 × LOQ) yielded satisfactory recoveries for all tested analytes in the range of 83.01 to 110.18% with relative standard deviation (RSD) ≤ 8.91. The method was successfully applied to field-incurred plum samples and dinotefuran and all metabolites were positively detected and quantified. In conclusion, we suggest that the method can be expanded to polar compounds having solvent and partitioning problems in any of the versions of QuEChERS. [ABSTRACT FROM AUTHOR]

A reliable and highly sensitive screening method based on liquid chromatography coupled with triple-quadrupole electrospray tandem mass spectrometry (LC-MS/MS) analysis has been developed for the detection and quantification of three veterinary drugs, including buparvaquone, nystatin, and etomidate impurity B CRS. The tested drugs were extracted from samples of porcine muscle, pasteurized whole milk, and eggs using 10 mM ammonium formate in acetonitrile followed by liquid-liquid purification with n -hexane. Chromatographic separation was achieved on a Phenomenex Luna C18 analytical column using 0.1% formic acid in ultrapure water (A) and acetonitrile (B) as mobile phases. All the matrix-matched calibration curves were linear ( R 2 ≥ 0.9756) over the concentration levels of the drugs tested. Recovery at two spiking levels (equivalent to the limit of quantification (LOQ) = 5 ng/g and 2 × LOQ) ranged from 72.88% to 92.59% with intra- and inter-day precisions <17%, except for porcine muscle spiked with 5 ng/g nystatin (RSD = 25.15%). Samples collected from markets located in Seoul, Republic of Korea, tested negative for all the drugs analyzed. In summary, this method is suitable for screening and quantifying the selected drugs in a single chromatographic run and with high selectivity in animal-derived food products meant for human consumption. [ABSTRACT FROM AUTHOR]