Detection of paraquat in oral fluid, plasma, and urine by capillary electrophoresis for diagnosis of acute poisoning.

The aim of this work was to develop a simple and fast method for the detection of paraquat in oral fluid, plasma, and urine by capillary electrophoresis with diode-array detection (CE-DAD), to diagnose of acute poisoning related to this herbicide. The use of oral fluid in analytical toxicology has been established for drugs of abuse, but not for diagnosis of pesticides poisoning. Oral fluid was collected without stimulation using absorbent cotton swabs. Sample preparation included diluting, vortex mixing, and centrifuging of biological fluid, using ethyl paraquat as internal standard. CE-DAD analyses were performed in a fused-silica capillary, and separation was performed under constant voltage condition of 21 kV, with detection at 195 nm. The electrolyte was a 40 mmol/L phosphate buffer at pH 2.50. The proposed method provided a fast and simple assay for the determination of paraquat in human oral fluid, plasma, and urine. To our knowledge, this is the first mention of use of oral fluid as a biological fluid diagnosis of quaternary ammonium herbicide poisoning. After validation, the method was applied to two cases of acute poisoning by this herbicide.