Determination of paraquat in blood and urine by liquid chromatography-electrospray-mass spectrometry

Abstract

Paraquat (PQ) is a toxic quaternary ammonium compound widely used in agriculture. Numerous cases of paraquat intoxication have been reported either accidentally or intentionally as suicidal attempts. A method for the determination of the herbicide PQ in blood and urine samples was developed using liquid chromatography-(electrospray ionization) mass spectrometry (LCESI-MS), following extraction with Oasis® WCX solid-phase cartridges. Chromatographic separation was achieved using an Atlantis® HILIC silica column, eluted isocratically with acetonitrile and ammonium formate (200mM) buffer, pH 3.8, at a 300 µL/min flow rate. Quantitation was achieved by the addition of ethyl paraquat as internal standard (IS). The compounds were detected monitoring two ions for PQ (m/z 185 and m/z 171) and m/z 213 for the IS. The method was applied to determine PQ in two cases: a non fatal case, a 42-year-old female with 0.13 µg/mL PQ concentration in blood and 6.29 µg/mL in urine and a lethal case, a 51-year-old male with 0.27 µg/ mL PQ concentration in blood. The authors developed a specific, sensitive and rapid assay for the identification and quantification of PQ, very important for monitoring suspected paraquat intoxications in hospitals and subsequently help in the treatment of these patients.