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In order to evaluate the efficiency of biobeds on DTC degradation, the aim of this study was to apply, optimize and validate a method to determine dithiocarbamate (mancozeb) in biobeds using gas chromatography-tandem mass spectrometry (GC-MS). The DTC pesticide mancozeb was hydrolysed in a tin (II) chloride solution at 1.5% in HCl (4 mol L -1 ), during 1 h in a water bath at 80 °C, and the CS 2 formed was extracted in isooctane. After cooling, 1 mL of the organic layer was transferred to an auto sampler vial and analyzed by GC-MS. A complete validation study was performed and the following parameters were assessed: linearity of the analytical curve (r 2 ), estimated method and instrument limits of detection and limits of quantification (LODm, LODi, LOQm and LOQi, respectively), accuracy (recovery%), precision (RSD%) and matrix effects. Recovery experiments were carried out with a standard spiking solution of the DTC pesticide thiram. Blank biobed (biomixture) samples were spiked at the three levels corresponding to the CS 2 concentrations of 1, 3 and 5 mg kg -1 , with seven replicates each (n = 7). The method presented satisfactory accuracy, with recoveries within the range of 89-96% and RSD ≤ 11%. The analytical curves were linear in the concentration range of 0.05-10 µg CS 2 mL -1 (r 2 > 0.9946). LODm and LOQm were 0.1 and 0.5 mg CS 2 kg -1 , respectively, and the calculated matrix effects were not significant (≤ 20%). The validated method was applied to 80 samples (biomixture), from sixteen different biobeds (collected at five sampling times) during fourteen months. Ten percent of samples presented CS 2 concentration below the LOD (0.1 mg CS 2 kg -1 ) and 49% of them showed results below the LOQ (0.5 mg CS 2 kg -1 ), which demonstrates the biobeds capability to degrade DTC., (Copyright © 2018 Elsevier B.V. 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.)

A fast and efficient multimethod for the determination of 36 mycotoxins in wine, using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), was developed, optimized, validated and implemented in routine analysis. A simplified, quick extraction was performed with acetonitrile, derived from the QuEChERS (quick, easy, cheap, effective, rugged and safe) approach, which was traditionally developed for pesticides analysis. This study aimed at a single extraction and chromatographic separation for 36 mycotoxins. Optimization tests were performed to find the proper ratio of wine: water and extraction solvent and the need for an additional buffering step with ammonium formate/formic acid and a dispersive SPE cleanup with various sorbents. The dSPE steps did not show significant improvement in analysis results, therefore, it was not applied in the final method to be validated. The mycotoxins were separated and detected on a UPLC-MS/MS system, used in the ESI positive ionization mode. The various mycotoxins were divided in three different concentration level groups, according to their sensitivity in UPLC-MS/MS. The validation was performed by analyzing recovery samples at three different spike levels with six replicates (n=6) at each level. Linearity (r(2)) of calibration curves, accuracy (recovery %), instrument limits of detection and method limits of quantification (LOD and LOQ), precision (RSD%) and matrix effects (%) were determined for each individual mycotoxin. From the 36 mycotoxins analyzed by UPLC-MS/MS (ESI+), 35 showed average recoveries in the range 70-120%, and 86% of these with a RSD≤20% at the lowest spike level (for Group I, II and III, respectively, 1, 50 and 10 µg kg(-1)). The higher spike levels showed even better results. Only nivalenol could not be quantified at any concentration level. The method LOQ for 86% of the mycotoxins studied was the lowest spike level tested. The matrix effect observed was low for most mycotoxins analyzed and had no significant influence on the analytical results obtained. The developed procedure was applied successfully in routine analysis in a survey of wine samples originating from different countries., (Copyright © 2014 Elsevier B.V. All rights reserved.)