A fast paraquat quantitation method in human serum using probe electrospray ionization–tandem mass spectrometry for emergency settings

Introduction: Paraquat (PQ) is one of the most toxic herbicides to humans. However, it is still in use in many countries, including Japan, and many incidents, such as homicides, intentional ingestions, and occupational accidents, have been reported thus far. In PQ poisoning cases, it is possible to predict severity and prognosis using nomograms. Therefore, if the serum PQ level is determined immediately, a treatment plan can be rapidly established. However, most known analytical methods are time-consuming and therefore hardly ever contribute to patient treatment. Methods: We developed a new method for PQ quantitation in serum by combining a probe electrospray ionization technique with mass spectrometry. This method requires virtually no serum pretreatment and can yield quantitation values in 18 s. Results: We applied the proposed method to samples from real poisoning cases and compared the results with those obtained via liquid-chromatography–tandem mass spectrometry, revealing the absence of any significant differences at the 5% significance level (t(8) = 1.000, p >.05). The limits of detection and quantitation were 0.004 and 0.015 μg/L, respectively, and the calibration curve exhibited good linearity over the concentration range of 0.015–4.0 μg/mL (r² = 0.998). Discussion: As the proposed method is fast and easy to perform, it should be useful in emergency medical settings.