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A reliable and highly sensitive detection method based on liquid chromatography coupled with triple quadrupole electrospray tandem mass spectrometry (LC-MS/MS) analysis has been developed for determination and quantification of halquinol, including 5,7-dichloroquinolin-8-ol and 5-chloroquinolin-8-ol. The target analytes were extracted from porcine muscle, egg, milk, eel, flatfish and shrimp using a mixture of acetonitrile and ethyl acetate followed by liquid-liquid purification with n-hexane. The analytes were separated on an Agilent Eclipse XDB-C 18 reversed-phase analytical column using 0.05% formic acid in distilled water and acetonitrile as mobile phases. Good linearity from six-point matrix-matched calibration was obtained with correlation coefficients (R 2 ) ≥ 0.9904. Recoveries from three spiking levels (5, 10 and 20 μg/kg) ranged between 70.6 and 101.7% in various matrices with relative standard deviations ≤8.6%. Samples acquired from markets located in Seoul, Republic of Korea, tested negative for the target analytes. In conclusion, the proposed method is versatile and precise for the routine detection of halquinol residual levels in animal-derived food products intended for human consumption., (© 2018 John Wiley & Sons, Ltd.)

A chromatographic method involving a single run was validated for the quantification of clanobutin, dichlorvos, and naftazone in products of animal origin. Pork, beef, chicken, milk, and egg samples were extracted with a solution of 0.1% formic acid in acetonitrile, defatted with n-hexane, centrifuged, and filtered prior to analysis using liquid chromatography-tandem mass spectrometry (LC-/MS/MS). The analytes were separated on a C18 column using a solution of 0.1% formic acid and 10 mM ammonium formate (A) and acetonitrile (B) as the mobile phase. A good linearity over 5-50 ng/g concentration range was obtained with coefficients of determination (R 2 ) ≥ 0.9807. The intra- and interday accuracy (recovery %) calculated from 3 fortification levels (5, 10, and 20 ng/g) were 73.2-108.1% and 71.4-109.8%, and the precisions (expressed relative standard deviations (RSDs)) were 0.9-12.9% and 1.8-10.6%, respectively, for the 3 tested analytes in animal originated foods. The limits of quantification (LOQs) ranged between 0.1 and 1 ng/g, thus enabling the quantification of residual levels below the uniform maximum residue limit (MRL) of 0.01 mg/kg set for compounds having no MRL. The designated methodology was successfully applied to monitor various samples collected from Seoul; the tested analytes were not quantified in any of the market samples. Conclusively, the developed method is simple, sensitive, and accurate, and could be used for the detection of pharmaceuticals in various animal food matrices with variable protein and fat contents., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Over the past few decades, honey products have been polluted by different contaminants, such as pesticides, which are widely applied in agriculture. In this work, a modified EN - quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction method was developed for the simultaneous quantification of pesticide residues, including cymiazole, fipronil, coumaphos, fluvalinate, amitraz, and its metabolite 2,4-dimethylaniline (2,4-DMA), in four types of honey (acacia, wild, chestnut, and manuka) and royal jelly. Samples were buffered with 0.2M dibasic sodium phosphate (pH 9), and subsequently, acetonitrile was employed as the extraction solvent. A combination of primary secondary amine (PSA) and C18 sorbents was used for purification prior to liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI + /MS-MS) analysis. The estimated linearity measured at six concentration levels presented good correlation coefficients (R 2 )≥0.99. The recovery, calculated from three different spiking levels, was 62.06-108.79% in honey and 67.58-106.34% in royal jelly, with an RSD<12% for all the tested compounds. The matrix effect was also evaluated, and most of the analytes presented signal enhancement. The limits of quantification (LOQ) ranged between 0.001 and 0.005mg/kg in various samples. These are considerably lower than the maximum residue limits (MRL) set by various regulatory authorities. A total of 43 market (domestic and imported) samples were assayed for method application. Among the tested samples, three samples were tested positive (i.e. detected and quantified) only for cymiazole residues. The residues in the rest of the samples were detected but not quantified. We concluded that the protocol developed in this work is simple and versatile for the routine quantification of cymiazole, 2,4-DMA, fipronil, coumaphos, amitraz, and fluvalinate in various types of honey and royal jelly., (Copyright © 2017 Elsevier B.V. All rights reserved.)

An analytical method was developed for the detection of toldimfos sodium residues in porcine muscle and bovine milk using liquid chromatography-triple quadrupole tandem mass spectrometry (LC-MS/MS) analysis. The drug was extracted from muscle and milk using 10 mm ammonium formate in acetonitrile and then purified using n-hexane. The drug was well separated on a Luna C 18 column using a mixture of 10 mm ammonium formate in ultrapure water (A) and acetonitrile (B) as the mobile phase. Good linearity was achieved over the tested concentration range (0.005-0.03 mg/kg) in matrix-matched standard calibration. The determination coefficients (R 2 ) were 0.9942 and 0.9898 for muscle and milk, respectively. Fortified porcine muscle and bovine milk contained concentrations equivalent to and twice the limit of quantification (0.005 mg/kg) yielded recoveries in the range of 75.58-89.74% and relative standard deviations of ≤8.87%. Samples collected from large markets located in Seoul, Republic of Korea, tested negative for toldimfos sodium residue. In conclusion, ammonium formate in acetonitrile can effectively extract toldimfos sodium from porcine muscle and bovine milk without solid-phase extraction, which is usually required for cleanup before analysis. This method can be applied for the routine analysis of toldimfos in foods of animal origins., (Copyright © 2017 John Wiley & Sons, Ltd.)

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.)