[Determination of endosulfans and its metabolite in fishery foods using gas chromatography-mass spectrometry with negative ion chemical ionization].

Endosulfan is one of the organochliorine pesticides and contains two stereoisomers, alpha-endosulfan and beta-endosulfan. Endosulfan sulfate is the oxide of endosulfan with toxicity comparable to endosulfan. The method was developed for the analysis of alpha-endosulfan, beta-endosulfan and endosulfan sulfate in fishery foods. Since the maximal residue level is set at about 4 - 6 microg/kg in many countries, the acceptable method must be sensitive and accurate. The conditions were systematically optimized and external standard method was used for the quantification. The sample was extracted by acetone and hexane (1 : 1, v/v), removed fat by transfering to acetonitrile and cold, and cleaned up with an Envi-Carb column and an LC-Alumina-N column, and analyzed by gas chromatography-mass spectrometry negative ion chemical ionization with selective ion mode. The selective ions of endosulfans and endosulfan sulfate were m/z 406, 408, 404, 372 and m/z 386, 388, 384, 422, respectively. The lowest quantitative limited level of every compound was 0. 5 microg/kg, and the recoveries were 83% - 105%, and the relative standard deviations were less than 13%. The method is efficient, accurate and sensitive to meet the requirements for determining endosulfans in fishery foods.