Analysis of endosulfan and its metabolites in human serum using gas chromatography-tandem mass spectrometry

A new analytical method combining solid-phase extraction and gas chromatography-tandem mass spectrometry (GC-MS-MS) is proposed to determine the insecticide endosulfan as well as its metabolites endosulfan-ether, -lactone, and -sulfate in human serum. Most matrix interferences are avoided using a cleanup step included in the sample treatment and an instrumental technique such as GC-MS-MS, which presents a high sensitivity and selectivity. Recoveries of spiked compounds range between 94.8 and 100.4% and 93.4 and 99.7% at fortification levels of 10 and 30 ng/mL, respectively. The relative standard deviation is lower than 17.6% in all cases, and the limits of detection calculated range from 6 to 19 pg/mL. Serum samples of nine agricultural workers that spray endosulfan into greenhouses in Almería (Spain) and two nonoccupationally exposed people are analyzed, and endosulfan is found in all the samples studied.