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This work presents an easy and quick miniaturized procedure for the analysis of dithiocarbamates fungicides (DTC), by GC-MS, in yerba mate, an important product in South America. The sample amount, the volume of extracting solvent and acid solution, and the time of hot bath shaking were minimized. A clean-up procedure based on PSA, GCB and MgSO4 was studied in order to improve analytical signal and reduce GC-MS system damage. Blank yerba mate samples were spiked with thiram at equivalent CS 2 concentrations of 0.1, 0.3, 0.5 and 1 mg kg -1 . The validated method at least 2 times faster than the traditional method and was according to the latest European guidelines for pesticide residue analysis. Linearity, limits of detection and quantification, matrix effects, trueness and precision were assessed. Sixty-five commercialized samples from southern Brazil and Argentina were analyzed; 14% of samples presented CS 2 concentration greater than LOQ (0.1 mg kg -1 )., (Copyright © 2022. Published by Elsevier Ltd.)

Food matrices consist of many components with different physical and chemical properties that may influence instrumental robustness. The soybean contains fatty coextractives which may have a deleterious effect on the gas chromatography (GC) system. In this study, the efficiencies of PSA, C 18 OH, C 18 , silica, aluminum oxide, and Florisil, as dSPE clean-up sorbents, were evaluated by the high-performance liquid chromatography (HPLC) diode-array detector and evaporative light-scattering detector analysis. The dithiocarbamates in soybean samples are determined as CS 2 using acidic hydrolysis and isooctane partitioning, followed by GC-PFPD and GC-ITD-MS analyses. The linearity of the analytical curves, the instrument limit of detection matrix effects, the trueness and precision, and the method limit of quantification (LOQ) were assessed in the validation study. Milled soybean was spiked with thiram solution at three concentration levels (corresponding to 0.05, 0.1, and 0.5 mg CS 2 kg -1 ) for recovery determination. Silica appeared to be an effective and cheap sorbent to remove coextracted matrix components without causing any CS 2 losses. Recoveries were in the range of 68-91%, with relative standard deviations ≤ 8.7%. The method LOQ was 0.05 mg CS 2 kg -1 , and both GC-ITD-MS and GC-PFPD systems appeared to be appropriate and complementary to determine dithiocarbamate residues in soybean extracts.

A quick and efficient method was optimized and validated to determine chlorpyrifos in biobeds using ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). Chlorpyrifos was extracted from the matrix with 30 mL of a mixture of acetone, phosphoric acid and water 98:1:1 (v/v/v). After homogenization, centrifugation and filtration, 125 µL of the extract was evaporated and reconstituted in 5 mL of methanol acidified with 0.1% acetic acid. Validation was performed by studying analytical curve linearity (r 2 ), estimated instrument and method limits of detection and limits of quantification (LOD i , LOD m , LOQ i and LOQ m , respectively), accuracy, precision (expressed as relative standard deviation, RSD), and matrix effect. Accuracy and precision were determined from the amount of pesticide recovered from biobed blank samples (i.e. without pesticide residue) spiked with chlorpyrifos at three different concentrations (2, 10 and 50 mg kg -1 ), with seven replicates at each concentration. For all three concentrations studied, the average recovery values obtained were between 96 and 115% with RSD values lower than 20%. The validated LOQ obtained was 2 mg kg -1 (from recovery studies) and the matrix effect observed was lower than ±20%, which demonstrated that there was neither considerable suppression nor enhancement of the analyte signal. The biobed system efficiently degraded chlorpyrifos in both 1) simulation of accidental spillage and 2) application of diluted pesticide solution. In the latter case, all the values obtained at the final sampling time (14 months) were below the validated LOQ m ., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: Common bean is a staple food in Latin America and Africa; however, studies about contamination of common bean with pesticides are rarely reported. So, the goals of this study were to validate a multiresidue method and apply it in monitoring of pesticides in common beans. Extraction was performed applying the QuEChERS (quick, easy, cheap, effective, rugged, and safe) approach to ground samples. Octadecylsilane and primary-secondary amine were used for clean-up, and a solvent exchange step was performed before injection for gas chromatography-tandem mass spectrometry analysis. Method validation was done analyzing blank samples spiked at 20, 30, 50, and 100 μg kg -1 (n = 5). Linearity and linear range were assessed by the analysis of standard solutions at concentrations of 5, 15, 25, 50, 75, 100, and 150 μg L -1 ., Results: The method was successfully validated for 91 (64.1%) of the 142 compounds studied (139 pesticides and three degradation products). Limits of quantification were equal to 20 μg kg -1 , 30 μg kg -1 , 50 μg kg -1 , and 100 μg kg -1 for 18 (12.7%), 17 (12.0%), 21 (14.8%) and 35 (24.6%) compounds respectively. Fifteen (10.6%) compounds were not detected at any level, and 36 (25.4%) did not fulfill the requirements for a quantitative method. Sixteen common bean samples of South of Brazil were analyzed. Two samples were positive: one for tebuconzole and a second for picoxystrobin, permethrin, and cyproconazole. Cyproconazole is not allowed for use in the common bean crop, its use being a violation., Conclusion: As demonstrated, the validated approach is suitable for pesticide residues determination in common bean. Results of the sample analysis show that the control of pesticide residues in common bean is necessary to ensure food safety. © 2020 Society of Chemical Industry., (© 2020 Society of Chemical Industry.)

This study describes the optimization and single-laboratory validation of a single residue method for determination of two bipyridylium herbicides, paraquat and diquat, in cowpeas by UPLC-MS/MS in a total run time of 9.3min. The method is based on extraction with an acidified methanol-water mixture. Different extraction parameters (extraction solvent composition, temperature, sample extract filtration, and pre-treatment of the laboratory sample) were evaluated in order to optimize the extraction method efficiency. Isotopically labeled internal standards, Paraquat-D6 and Diquat-D4, were used and added to the test portions prior to extraction. The method validation was performed by analyzing spiked samples at three concentrations (10, 20 and 50μgkg(-1)), with seven replicates (n=7) for each concentration. Linearity (r(2)) of analytical curves, accuracy (trueness as recovery % and precision as RSD%), instrument and method limits of detection and quantification (LOD and LOQ) and matrix effects were determined. Average recoveries obtained for diquat were between 77 and 85% with RSD values ⩽20%, for all spike levels studied. On the other hand, paraquat showed average recoveries between 68 and 103% with RSDs in the range 14.4-25.4%. The method LOQ was 10 and 20μgkg(-1) for diquat and paraquat, respectively. The matrix effect was significant for both pesticides. Consequently, matrix-matched calibration standards and using isotopically labeled (IL) analogues as internal standards for the target analytes are required for application in routine analysis. The validated method was successfully applied for cowpea samples obtained from various field studies., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In this study, a very sensitive method was validated to determine pesticides residues in fruit jams using micro flow liquid chromatography-tandem mass spectrometry (µLC-MS/MS). A slurry of the fruit jams and water was prepared to yield homogeneous samples. Because of the high sensitivity achieved with the µLC-MS/MS equipment and to minimize matrix effects, the QuEChERS extracts were diluted 30-fold before the analysis. The validation was performed analyzing spiked samples at 9 and 45 µg kg(-1) (n=5). The method met validation criteria of 70-120% recovery and RSD≤20% for 92% of the 107 pesticides evaluated. The reporting limit (RL) was 9 and 45 µg kg(-1) for respectively 66% and 26% of the analytes, 5% of the compounds did not fulfill the requirements for validation and 3% were not detected at the studied concentrations. The validated method was applied to the analysis of 51 different fruit jam samples from Brazil and Spain and pesticide residues were detected in 41 samples, 26 of which contained at least one pesticide at concentration >10 µg kg(-1)., (Copyright © 2014 Elsevier B.V. All rights reserved.)

In this study, a new gas chromatography-mass spectrometry (GC-MS) method, using the very selective negative chemical ionization (NCI) mode, was developed and applied in combination with a modified acetonitrile-based extraction method (QuEChERS) for the analysis of a large number of pesticide residues (51 pesticides, including isomers and degradation products) in green coffee beans. A previously developed integrated sample homogenization and extraction method for both pesticides and mycotoxins analysis was used. An homogeneous slurry of green milled coffee beans and water (ratio 1:4, w/w) was prepared and extracted with acetonitrile/acetic acid (1%), followed by magnesium sulfate addition for phase separation. Aliquots from this extract could be used directly for LC-MS/MS analysis of mycotoxins and LC-amenable pesticides. For GC-MS analysis, a further clean-up was necessary. C18- and PSA-bonded silica were tested as dispersive solid-phase extraction (d-SPE) sorbents, separate and as a mixture, and the best results were obtained using C18-bonded silica. For the optimal sensitivity and selectivity, GC-MS detection in the NCI-selected ion monitoring (SIM) mode had to be used to allow the fast analysis of the difficult coffee bean matrix. The validation was performed by analyzing recovery samples at three different spike concentrations, 10, 20 and 50 μg kg(-1), with 6 replicates (n=6) at each concentration. Linearity (r(2)) of calibration curves, estimated instrument and method limits of detection and limits of quantification (LOD(i), LOD(m), LOQ(i) and LOQ(m), respectively), accuracy (as recovery %), precision (as RSD%) and matrix effects (%) were determined for each individual pesticide. From the 51 analytes (42 parent pesticides, 4 isomers and 5 degradation products) determined by GC-MS (NCI-SIM), approximately 76% showed average recoveries between 70-120% and 75% and RSD ≤ 20% at the lowest spike concentration of 10 μg kg(-1), the target method LOQ. For the spike concentrations of 20 and 50 μg kg(-1), the recoveries and RSDs were even better. The validated LOQ(m) was 10, 20 and 50 μg kg(-1) for respectively 33, 3 and 6 of the analytes studied. For five compounds, the European Union method performance requirements for the validation of a quantitative method (average recoveries between 70-120% and repeatability RSD ≤ 20%) were not achieved and 4 problematic pesticides (captan, captafol, folpet and dicofol) could not be detected as their parent compound, but only via their degradation products. Although the matrix effect (matrix-enhanced detector response) was high for all pesticides studied, the matrix interference was minimal, due to the high selectivity obtained with the GC-NCI-MS detection. Matrix-matched calibration for applying the method in routine analysis is recommended for reliable quantitative results., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Two simple and straightforward sample preparation methods were developed for the multiresidue analysis of post-emergence herbicides in loam soil that are commonly used in rice crop cultivation. A number of strategic soil extraction and cleanup methods were evaluated. The instrumental analysis was performed by HPLC with a diode array detector. The best compromise between the recoveries (69-98%) and good repeatability (RSD < 15%) was obtained using either methanol or methanol-ethyl acetate (70 + 30, v/v) as extraction solvents without any further cleanup. For the first time, residues of metsulfuron methyl, bensulfuron ethyl, bentazone, cyhalofop butyl, pyrazosulfuron ethyl, propanil, and clomazone were analyzed simultaneously. Quinclorac and bispyribac sodium were also assayed, but their recoveries were below 50%. Both methods had an LOD of 0.7 microg/kg and could accurately determine the residues at the 2 microg/kg level. These two methods could not be applied directly to other soil types as the recoveries strongly depended on the soil composition. The developed methodologies were successfully applied in monitoring 87 real-world soil samples, in which only propanil (6 to 12 microg/kg) and clomazone (15 to 20 microg/kg) residues could be detected.

In this study, a new modulator that is simple, robust and presents low operation costs, was developed. This modulator uses compressed air to cool two small portions in the first centimeters of the second chromatographic column of a comprehensive multidimensional gas chromatography (GCxGC) system. The results show a variation in the peak area less than 3 and 5% to alkanes and pesticides, respectively. The standard deviations for the retention times in the first and second dimension are around 0.05 min and 0.05s for all the compounds. The system was optimized with n-alkanes. The GCxGC system proposed was applied in the determination of pyrethroid pesticides (bifenthrin, cypermethrin, deltamethrin, fenvalerate, esfenvalerate, cis- and trans-permethrin) in grape samples. Samples were extracted by the mini-Luke modified method and pesticides were quantified by comprehensive multidimensional gas chromatography with micro electron-capture detection (microECD). The values of method limit of quantification (LOQ) were 0.01-0.02 mg kg(-1) for all studied pyrethroid and the values of recovery were between 94.3 and 115.2%, with good precision (RSD<18.4%), demonstrating that the performance of the total method consisting of a modified Luke extraction method and determination by GCxGC-microECD are satisfactory. This study also showed that the system using a modulator with a double jet of compressed air has the potential for application in the analysis of a wider range of pesticide residues in other commodities since it provides low values of LOQ with acceptable accuracy and precision.