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A comparative study was conducted to replace the traditional screening method (MFDS#83) with the Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) EN method for the determination of 267 pesticides/metabolites/plant activators/growth regulators in five representative crop matrices (mandarin, pepper, potato, rice, and soybean). In the traditional method, samples were extracted with acetonitrile and salt, and purified with a solid-phase extraction cartridge. In the QuEChERS method, the sample extraction was carried out using acetonitrile and a mixture of salts, and purification was performed using dispersive solid phase extraction. The limit of quantification (LOQ) for the MFDS#83 method was 0.0004 mg/kg, whereas for the QuEChERS EN method, the LOQ varied from 0.002 to 0.006 mg/kg for all analytes in various matrices. A six-point matrix-matched calibration curve was prepared for all analytes in five matrices for both methods. Both the MFDS#83 and QuEChERS EN methods provided excellent linearity, with the coefficients of determination (R 2 ) ≥ 0.99 for most of the compounds. In both cases, the method was validated in terms of recovery and repeatability after the fortification of two different concentrations with three replicates for each of the concentrations. The QuEChERS EN method provided better recovery than the MFDS#83 method for all matrices except mandarin., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A simultaneous analytical method was developed for the determination of methiocarb and its metabolites, methiocarb sulfoxide and methiocarb sulfone, in five livestock products (chicken, pork, beef, table egg, and milk) using liquid chromatography-tandem mass spectrometry. Due to the rapid degradation of methiocarb and its metabolites, a quick sample preparation method was developed using acetonitrile and salts followed by purification via dispersive- solid phase extraction (d-SPE). Seven-point calibration curves were constructed separately in each matrix, and good linearity was observed in each matrix-matched calibration curve with a coefficient of determination (R 2 ) ≥ 0.991. The limits of detection and quantification were 0.0016 and 0.005mg/kg, respectively, for all tested analytes in various matrices. The method was validated in triplicate at three fortification levels (equivalent to 1, 2, and 10 times the limit of quantification) with a recovery rate ranging between 76.4-118.0% and a relative standard deviation≤10.0%. The developed method was successfully applied to market samples, and no residues of methiocarb and/or its metabolites were observed in the tested samples. In sum, this method can be applied for the routine analysis of methiocarb and its metabolites in foods of animal origins., (Copyright © 2017 Elsevier B.V. All rights reserved.)

An analytical method has been developed to quantify the residual levels of sulfoxaflor and its metabolites (X11719474 and X11721061) in/on cultivated lettuce grown under greenhouse conditions. Samples were extracted and purified using a quick, easy, cheap, effective, rugged, and safe 'QuEChERS' method (original version) following systematic method optimization and were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Good linearity with coefficient of determination ≥0.9930 was obtained and the limits of detection (LOD) and quantification (LOQ) were in the ranges of 0.003-0.006 and 0.01-0.02 mg/kg, respectively. The recovery rates of both the parent compound and its metabolites (fortified at 10 and 50× the LOQ) estimated from six replicates ranged between 81.9 and 115.5% with a relative standard deviation <12%. The validated method was applied to field-incurred samples (collected over 7 days) sprayed once or twice with a water-dispersible granule formulation. Notably, a substantial reduction in rate was observed after 3 days and the half-life was short, only 1.5 days. The developed method is simple and versatile and can be used for various leafy vegetables., (Copyright © 2016 John Wiley & Sons, Ltd.)

An effective analytical method was developed for the detection and quantification of polyoxin D in butterbur using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Samples were extracted using acidified deionised water and purified via solid-phase extraction (SPE) using an HLB cartridge. An external matrix-matched standard calibration curve was prepared, which provided an excellent linearity with a coefficient of determination (R 2 ) ⩾0.999. Limits of detection (LOD) and quantification (LOQ) were 0.015 and 0.0.05μg/g, respectively. The developed method was validated in terms of recovery performance using two fortification levels in triplicate. The storage stabilities of the various field samples were also determined. Our method provided consistent recovery (86.26-87.37%) with a relative standard deviation (RSD) of <5%, and was successfully applied to field-treated butterbur grown under greenhouse conditions and collected at various times following commercial fungicide application. As expected, a gradual degradation of polyoxin D was observed, with a half-life (t 1/2 ) of 2.11d being recorded. Finally, we propose that the developed method can be extrapolated to other crops for routine analysis and can be used to determine the pre-harvest intervals (PHIs), thus preventing the development of antibiotic resistance genes in humans and in the environment., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

A high-performance liquid chromatography-fluorescence detection method was developed for the simultaneous determination of thiodicarb and its degradation product methomyl in animal-derived food products, including chicken muscle, beef, pork, table eggs, and milk. Thiodicarb is known to degrade during analysis; therefore, a thorough investigation was carried out, revealing that thiodicarb degrades to methomyl immediately after spiking into a matrix of animal-derived food products. Consequently, thiodicarb was determined as the sum of the parent compound and methomyl. Samples were extracted with acetonitrile and sodium salts, and purified using solid-phase extraction (SPE). The limits of detection (LODs) and quantification (LOQs) were 0.0013 and 0.004mg/kg, respectively, for both analytes in various matrices. Seven-point external calibration curves were obtained, and they showed excellent linearity with determination coefficients (R 2 )≥0.999 for all tested matrices. The method was validated at three fortification levels (LOQ, LOQ×2, and LOQ×10) in triplicate with average recoveries ranging from 84.24 to 112.8% (for methomyl) and relative standard deviations (RSDs)≤6.5% in all matrices. The converted recoveries of thiodicarb in various matrices ranged from 74.80 to 107.80% with RSDs≤4.5%. The identities of both compounds in standard solutions and for recovery were confirmed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The developed method was further validated by accurate reproduction at another laboratory. Finally, the method was applied to market samples collected from different areas (and, in the case of milk, different brands), and none of the samples tested positive for thiodicarb or methomyl. In conclusion, the developed method can be successfully applied for a single-run analysis of thiodicarb and methomyl in livestock products., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In this study, the original Quick, Easy, Cheap, Effective, Rugged and Safe method was used for the extraction of imidacloprid and pyrimethanil followed by a rapid clean-up through dispersive solid-phase extraction technique with primary secondary amine sorbent and magnesium sulfate in shallot. Residues were analyzed using LC-tandem mass spectrometry in positive-ion electrospray ionization mode. The limits of detection and quantification were estimated to be 0.006 and 0.02 mg/kg, respectively. The samples were fortified at two different concentration levels (0.2 and 1.0 mg/kg), and the recoveries ranged between 79.7 and 83.9% with relative standard deviation values < 6%. The method was successfully applied for the establishment of the pre-harvest residue limits (PHRL). The rate of disappearance of imidacloprid and pyrimethanil on shallot was described with first-order kinetics (imidacloprid, y(2)  = 0.9670; pyrimethanil, y(2)  = 0.9841), with half-lives of 2.87 and 2.08 days, respectively. Based on the dissipation patterns of the pesticide residues, the PHRL was recommended at 7.86 mg/kg for 14 days (PHRL14 ) and 1.98 mg/kg for 7 days (PHRL7 ) before harvest for imidacloprid, and 21.64 mg/kg for 7 days (PHRL7 ) and 9.28 mg/kg for 4 days (PHRL4 ) before harvest for pyrimethanil in shallot., (Copyright © 2012 John Wiley & Sons, Ltd.)

In this study, a simultaneous method was developed for the determination of spinetoram (XDE-175-J and XDE-175-L) and its demethyl metabolites (N-demethyl-175-J and N-demethyl-175-L) and formyl metabolites (N-formyl-175-J and N-formyl-175-L) in the minor crops; amaranth and parsley. The method uses quick, easy, cheap, effective, rugged, and safe (QuEChERS)-based extraction. Afterwards, the analytes were quantified and confirmed via liquid chromatography-electrospray ionisation tandem mass spectrometry (LC-ESI-MS/MS) in the positive ion mode using multiple reaction monitoring (MRM). Calibration curves were linear over the calibration ranges for all the analytes tested with r(2)>0.993. Limits of detection and quantitation were 0.01 and 0.03 mg/kg for all the tested analytes in amaranth and parsley, respectively. Recovery values, at spiking levels 0.05 and 0.25 mg/kg, ranged from 71.0% to 115.2% with relative standard deviations <15%, except for N-formyl-175-J in both amaranth and parsley. This method was applied to field-incurred samples and was shown to provide an adequate sensitivity and performance for the simultaneous determination of spinetoram and metabolites. To the best of our knowledge, this is the first time spinetoram and its metabolites were quantified using LC-MS/MS in minor crops., (Copyright © 2012 Elsevier Ltd. All rights reserved.)