Accurate determination of selected pesticides in soya beans by liquid chromatography coupled to isotope dilution mass spectrometry

Abstract

A sensitive, accurate and simple liquid chromatography coupled with mass spectrometry method for the determination of 10 selected pesticides in soya beans has been developed and validated. The method is intended for use during the characterization of selected pesticides in a reference material. In this process, high accuracy and appropriate uncertainty levels associated to the analytical measurements are of utmost importance. The analytical procedure is based on sample extraction by the use of a modified QuEChERS (quick, easy, cheap, effective, rugged, safe) extraction and subsequent clean-up of the extract with C18, PSA and Florisil. Analytes were separated on a C18 column using gradient elution with water-methanol/2.5 mM ammonium acetate mobile phase, and finally identified and quantified by triple quadrupole mass spectrometry in the multiple reaction monitoring mode (MRM). Reliable and accurate quantification of the analytes was achieved by means of stable isotope-labelled analogues employed as internal standards (IS) and calibration with pure substance solutions containing both, the isotopically labelled and native compounds. Exceptions were made for thiodicarb and malaoxon where the isotopically labelled congeners were not commercially available at the time of analysis. For the quantification of those compounds methomyl-(13)C2(15)N and malathion-D10 were used respectively. The method was validated according to the general principles covered by DG SANCO guidelines. However, validation criteria were set more stringently. Mean recoveries were in the range of 86-103% with RSDs lower than 8.1%. Repeatability and intermediate precision were in the range of 3.9-7.6% and 1.9-8.7% respectively. LODs were theoretically estimated and experimentally confirmed to be in the range 0.001-0.005 mg kg(-1) in the matrix, while LOQs established as the lowest spiking mass fractionation level were in the range 0.01-0.05 mg kg(-1). The method reliably identifies and quantifies the selected pesticides in soya beans at appropriate uncertainty levels, making it suitable for the characterization of candidate reference materials.

Distribution and Elimination of Deltamethrin Toxicity in Laying Hens

“…Matrix effects in GC-MS methods can be influenced by various factors such as the chemical structure, concentration, and nature of the target being measured, as well as the type, concentration, acidity, and state of the matrix. To reduce these effects, several techniques have been reported including matrix-matching correction methods [28], isotope internal standard methods [29,30], addition of protectants/masking methods [31], and improvements to the injection technique. Matrix matching correction was employed in this study to mitigate the impact of matrix effects on the analysis results.…”

Simultaneous analysis of seven neonicotinoid pesticides in agricultural products involving solid-phase extraction and surrogate compensation using liquid chromatography-tandem mass spectrometry

“…These benefits of both accuracy and convenience made the calibration method applicable to various pesticide analyses. 22) Unfortunately, there is a limitation in the number of ISs that can be spiked for calibration in simultaneous analyses, because, for some pesticides, the ISs are not commercially available. In that case, an IS for the calibration is often chosen from other available isotope-labeled compounds that is similar to the target analyte in its property like a structure, chromatographic separation, or compound ionization.…”

“…In that case, an IS for the calibration is often chosen from other available isotope-labeled compounds that is similar to the target analyte in its property like a structure, chromatographic separation, or compound ionization. 22,23) Moreover, most ISs are costly, and thus it is desirable to choose a minimum number of ISs in order to perform simultaneous analysis with a reasonable cost. For the simultaneous analysis of seven neonicotinoid pesticides, imidacloprid-d 4 is often selected as the only IS for the compensation 9,10,13) ; however, its utility has not been scientifically eluci-…”

Method Validation for Organochlorine Insecticides Determination in Ginseng by Using Isotope-Dilution Gas Chromatography-Mass Spectrometry (Id-Gc-Ms)

“…The loss during extraction, clean-up, evaporation will not much affect the accuracy (Sargent et al, 2002). Some successful works employing ID-MS in the determination of organic substances have been published in recent years both GC-based or LC-based (Goldschmidt and Wolf, 2010;Bi et al, 2012;Huertas-Pérez et al, 2019;Huertas-Pérez et al, 2015;Bercaru et al, 2006). However, the challenge in the analysis still presents due to the complex matrix and the shallow maximum residue limits (MRLs) in some regulations.…”