Gabrieli Bernardi

A simple and efficient method for imidazolinone herbicides determination in soil by ultra-high performance liquid chromatography-tandem mass spectrometry.

The use of pesticides in agriculture has generated numerous consequences to the environment, requiring analysis of the persistent residues in soil, water and air. The variability of soil properties interferes in the extraction of pesticide residues with robustness and accuracy. The group of imidazolinones herbicides, widely used for weed control, becomes an additional task in multiresidue extraction procedures because of their low pKa values. In order to determine these compounds in soil samples, different methods have been proposed, however they can be very laborious and require more time and well trained analysts. Thus, this study aimed to develop a simple and efficient method for determination of imidazolinones (imazamox, imazapic, imazapyr, imazaquin and imazethapyr) residues in soil, using an extraction with aqueous ammonium acetate solution (0.5 M) and clean-up with dispersive solid phase extraction employing PSA, followed by UHPLC-MS/MS analysis. Satisfactory values of accuracy (70-93%) and RSD (≤17%) were achieved, as well as lower limit of quantification (5.0 μg kg(-1)). Considering the matrix and compounds complexity, the developed and validated method proved to be an excellent tool for rapid analysis (20 min), with reliability for application in real samples with wide pH range. In the analysis of 22 real samples, the method allowed the quantification of imazapic (5.84 and 12.1 μg kg(-1)), imazapyr (5.3 μg kg(-1)) and imazethapyr (24.0 and 37.7 μg kg(-1)) in three samples.

Optimization and validation of a multiresidue method for pesticide determination in maize using gas chromatography coupled to tandem mass spectrometry

A modified QuEChERS method was optimized for pesticide multiresidue extraction from maize for further GC-MS/MS determination. Extraction was conducted using a simultaneous hydration/extraction process. The clean-up step was performed using low temperature precipitation of lipids followed by dispersive solid-phase extraction (d-SPE). Low temperature precipitation at −18 °C during 12 hours enabled a reduction of co-extractives. Factorial experimental designs allowed the determination of optimum extraction and clean-up conditions. The proposed method was evaluated through the following analytical parameters: linearity, limits of detection (LOD) and quantification (LOQ), accuracy and precision. Results for the instrumental LOD and LOQ were 1.5 and 5.0 μg L−1, respectively, while the practical method LOQ was 40 or 100 μg kg−1 depending on the compounds. Recoveries from spike levels 40, 100 and 200 μg kg−1 were from 70 to 120% with RSD ≤ 20% for most compounds. Evaluation of the matrix effect was performed relating the areas of analytes in pure solvents to areas obtained from organic extracts. The results found were lower than 16.7%, confirming the efficiency of the proposed extraction and clean-up method.

An effective method for pesticide residues determination in tobacco by GC-MS/MS and UHPLC-MS/MS employing acetonitrile extraction with low-temperature precipitation and d-SPE clean-up

An effective method has been developed and validated for the determination of residues of 55 pesticides in tobacco. The proposed sample preparation method is based on acetonitrile extraction, low-temperature precipitation (LTP) and dispersive solid phase extraction (d-SPE) clean-up. Gas chromatography and ultra-high performance liquid chromatography analysis, both coupled to tandem mass spectrometry (GC-MS/MS and UHPLC-MS/MS), were used for determination. LTP is easy to perform and was crucial to obtain a clean extract. Method quantification limit for the pesticides were between 25 and 75µgkg-1. Extraction recoveries obtained for blank samples spiked at 25, 75, 125 and 250µgkg-1 levels ranged from 63 to 161% with relative standard deviations (RSD)≤20%. The method was successfully applied to the analysis of thirteen different tobacco samples, providing to be a robust procedure for routine analysis. The compounds pirimiphos methyl and isofenphos presented residues in the range of 35-51µgkg-1.

Evaluation of QuEChERS Sample Preparation and Gas Chromatography Coupled to Mass Spectrometry for the Determination of Pesticide Residues in Grapes

An effective analytical method for pesticides multiresidue determination in grape samples was developed and validated. A modified quick, easy, cheap, effective, robust and safe (QuEChERS) method was used to extract the target compounds. Several sorbent materials were tested for the clean-up step using dispersive solid phase extraction (d-SPE) and Florisil® was selected. Samples extracts were evaporated before injection in the gas chromatography with mass spectrometry (GC-MS) system in order to improve detectability. Recoveries from blank samples spiked at 0.04, 0.3 and 1.0 mg kg−1 ranged from 95 to 102% with relative standard deviation (RSD) from 1.3 to 19.7%. Method limits of detection (LODm) and quantification (LOQm) ranged from 0.006 to 0.012 and 0.02 to 0.04 mg kg−1, respectively. The positive matrix effect caused an increase in the peak areas of all compounds and matrix matched calibration curve linearity (coefficient of determination, r2) was higher than 0.98 for all target analytes. The validated method was successfully applied for the determination of 19 pesticides in grape samples.

Advanced Sample Preparation Techniques for Pesticide Residues Determination by HRMS Analysis

Abstract In modern agriculture, pesticides are widely used to control pests and weeds during crop cultivation and storage. Currently, over 1000 substances are used as pesticides across the globe. In addition, the selection and use of pesticides vary depending on the target crop, user, and country. The need to monitor pesticide residues in food has promoted the development of extraction methods that make possible to determine a large number of compounds in a single analysis. Different improvements have been made in this research area during the last 20 years. Among them hyphenated techniques with highly efficient separation and sensitive detection become the first choice. Even with powerful instrumental equipment, the risk of interference increases with the matrix complexity. In this way, sample preparation is still mandatory in many applications, for example, food analysis. Food samples present an enormous challenge to analytical chemists to determine pesticide residues at trace levels to satisfy worldwide food safety regulations. Sample preparation has always been considered as the bottleneck in the analytical laboratory performing numerous analyses, but it is the key to accurate analysis. Thus, a generally applicable screening method for multiresidue pesticide analysis in a large variety of foods, which is simple, quick, accurate, and reliable, is becoming increasingly important for both food safety and international trade. In addition, an ideal high-throughput screening system, which reduces the total time taken for analysis, is also economically beneficial. In the last years, high-resolution mass spectrometry (HRMS) combined with different sample preparation has attracted attention as a promising tool for multiresidue pesticide analysis. The objective of the current chapter is to present the most applied sample preparation techniques for pesticide residue analysis by chromatographic techniques combined with HRMS.

Fast Sample Preparation Method Using Ultra-High Performance Liquid Chromatography Coupled to Tandem Mass Spectrometry for Natamycin Determination in Wine Samples

An easy and efficient sample preparation method was developed for the determination of natamycin residues in wine samples by solvent extraction and ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) analysis. After choosing acetonitrile as extraction solvent, an experimental design was carried out with different amounts of C18 and primary secondary amine (PSA) sorbents in order to optimize the clean-up step. Validation results were satisfactory, with recoveries from 77 to 95% and relative standard deviation (RSD) lower than 10% for the spike levels 5, 10 and 20 µg L −1 . Method limit of detection (LOD) and quantification (LOQ) were 1.5 and 5.0 µg L −1 , respectively. The validated method proved to be an excellent analytical tool, with a total analysis time of 3 min. The method was applied in 10 Brazilian wine samples and no residues of natamycin were detected.