Abstract: Objective To determine the chlorpyrifos in human blood by liquid chromatography-tandem mass spectrometry and to validate its application in poisoning cases. Methods The samples were extracted by a simple one-step protein precipitation procedure. Chromatography was performed on a Capcell Pack C18 MGII column （250 mm×2.0 mm, 5 ?滋m） using an isocratic elution of solvent A （0.1% formic acid-water with 2 mmol/L ammonium acetate） and solvent B （methanol with 2 mmol/L ammonium acetate） at 5∶95 （V∶V）. Results The linear ranged from 5 to 500 ng/mL （r=0.998 7）. The limit of detection （LOD） and the lower limit of quantification （LLOQ） were 2 ng/mL and 4 ng/mL, respectively. For this method, the precision and accuracy of intra-day and inter-day were <10% and 97.44%-101.10%, respectively. The results in stability test of long-term frozen were satisfied. The matrix effect, recovery and process efficiency were 64.97%-86.81%, 76.70%-85.52%, and 55.57%-66.58%, respectively. Conclusion This method can provide a rapid approach to chlorpyrifos extraction and determination in toxicological analysis of forensic and clinical treatment.

Key words: forensic toxicology, chlorpyrifos, chromatography, high pressure liquid, tandem mass spectrometry, blood