Methodology for trace analysis of 17 pyrethroids and chlorpyrifos in foodstuff by gas chromatography-tandem mass spectrometry

This study aimed to develop an efficient, sensitive, and reliable analytical method for trace analysis of 17 different pyrethroids and chlorpyrifos in the fatty content of animal products, including beef, chicken, eggs, fish, and milk. The method developed is based on an ultrasound extraction using lyophilized samples, a solid phase extraction cleanup with basic alumina and C18 cartridges in tandem, and analysis by gas chromatography coupled to tandem mass spectrometry in negative chemical ionization mode. Recovery values were in the range of 27-128 % with relative standard deviation always below 25 %, and chiral analysis of recovery data showed predominance of isomers of cis form over trans. Limits of detection (LODs) ranged from 0.002 to 6.43 ng g(-1) lipid weight (lw), and limits of quantification (LOQs) ranged between 0.006 and 21.4 ng g(-1) lw. The developed methodology was used for the analysis of 25 samples of fatty foods. All samples were positive for at least one of the pesticides, chlorpyrifos, bifenthrin, cyhalothrin, permethrin, cypermethrin, or deltamethrin, with mass fraction levels ranging from 0.03 to 270 ng g(-1) lw.