[Screening method for the determination of 199 pesticides in agricultural products by gas chromatography/ion trap mass spectrometry (GC/MS/MS)]

Development of an enhanced analytical method utilizing pepper matrix as an analyte protectant for sensitive GC‒MS/MS detection of dimethipin in animal-based food products

Herein, an analytical method using gas chromatography-tandem mass spectrometry (GC‒MS/MS) was devised to detect the presence of the troublesome pesticide dimethipin in various animal-based food products, including chicken, pork, beef, eggs, and milk. The injection port was primed with a matrix derived from pepper leaves that acts as an analyte protectant (AP) to safeguard the target compound from thermal degradation during gas chromatography. The presence of AP resulted in a remarkable limit of quantification of 0.005 mg/kg for dimethipin in five matrices. Three different versions (original, EN, and AOAC) of the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method were compared for dimethipin extraction, with a double-layer solid-phase extraction (SPE) cartridge utilized for matrix purification. A seven-point external calibration curve was established for dimethipin in the five matrices, demonstrating excellent linearity with determination coefficients (R2) ≥ 0.998. The developed quantitative method was validated by fortifying each matrix with three different concentrations of standard dimethipin, and the average recovery fell within the acceptable range outlined in the CODEX guidelines (ranging from 88.8% to 110.0%), with a relative standard deviation (RSD) of ≤ 11.97%. This method effectively addresses the challenge of analyzing dimethipin and can therefore be used as a routine monitoring tool for dimethipin across various matrices.

Rapid multiresidue determination of pesticides in livestock muscle and liver tissue via modified QuEChERS sample preparation and LC-MS/MS

Many multiresidue methods for the determination of pesticides in vegetables and fruits have been reported to date. However, few such methods have been employed to investigate pesticide residues in animal tissue. In this study, an LC-MS/MS multiresidue method coupled with modified QuEChERS extraction was developed and validated for the investigation of eight pesticide residues: prallethrin (PR), resmethrin (RMT), imidacloprid (IMC), diflubenzuron (DFB), cyromazine (CYR), etofenprox (EFP), dinotefuran (DNT) and phthalthrin (PTLT). This method involves initial extraction in a water/acetone system, the addition of salts and a subsequent extraction/partitioning step and, finally, a clean-up step utilising dispersive solid-phase extraction (SPE). The mean recoveries of seven of the pesticides (the exception being CYR) ranged between 74.7% and 113.5%, and the CVs of the livestock tissue - bovine, swine, and chicken muscle and liver tissue spiked at 10 ng g^-1 (50 ng g^-1 for RMT and DNT) and 100 ng g^-1 - were < 13.8%. The recoveries of CYR in all muscle and liver spiked samples ranged from 56.9% to 78.3%, while those of RMT in swine liver were > 120%. Therefore, this method was considered as being unsuitable for the investigation of these samples. The limits of quantitation (LOQs) of seven of the investigated pesticides (the exception being swine liver) in the tissue samples ranged from 0.9 to 15.2 ng g^-1. We therefore concluded that this LC-MS/MS multiresidue method is a valid and suitable for the investigation of seven pesticides in animal tissue, but it is unsuitable for the analysis of CYR in all animal tissues and RMT in swine liver tissue.

[Determination of residual pesticides in processed foods manufactured from livestock foods and seafoods using ion trap GC/MS]

A simultaneous method using iontrap gas chromatography/mass spectrometry (GC/MS) was developed for the determination of pesticide residues in four processed foods (frozen Chinese dumpling, eel kabayaki, corned beef and retort curry). Pesticide residues were extracted from samples with ethyl acetate-cyclohexane (1:1) in the presence of anhydrous sodium sulfate. The extract was concentrated and the residue was dissolved in n-hexane. The lipids in the extract were removed by acetonitrile-n-hexane partitioning, following which the acetonitrile layer was cleaned up using a C(18) mini-cartridge column and a graphite carbon/PSA silica (GCB/PSA) mini-cartridge column. The limits of quantification of compounds in 4 processed foods were below 0.01 microg/g. The recoveries of 292 compounds spiked at 0.1 microg/g in 4 kinds of processed foods, and 210 to 262 pesticides showed acceptable recoveries of 70-120% with low repeatability (15%) and intermediate precision (<20%) only at the 0.1 microg/g spiked level. This method is expected to be useful for multi-residue analysis of pesticide residues in processed foods manufactured using livestock and seafoods as the main raw materials.