Rapid quantitative analysis of paraquat by electron spin resonance spectroscopy.

A very simple and sensitive method for quantitative measurement of paraquat in plasma, urine and some drinks is described. The paraquat radical formed by its reduction can be detected by electron spin resonance spectroscopy (ESR) at room temperature without clean-up or concentration process of samples. The sensitivity limit is 0.1 microgram paraquat/ml and the required amount of sample is 100 microliter. The time needed for the measurement is within 10 min.