Pesticide hair analysis: development of a GC-NCI-MS method to assess chronic exposure to diazinon in rats.

The present study aimed to improve the gas chromatography-mass spectrometry (GC-MS) method, already developed in our laboratory, for trace analysis of diazinon in hair. Furthermore, it aimed to compare the disposition of the pesticide in the hair of two different animal species, one susceptible to diazinon toxicity and one resistant, under identical experimental conditions. Sprague Dawley rats were systemically exposed to two dose levels (6 mg/kg/day and 3 mg/kg/day) of the pesticide, through their drinking water, for a period of one and a half months. Hair samples from the back of the rats were removed before commencing the experiment and at the end of the dosing period. Diazinon was selectively isolated from pulverized hair, sample or spiked, by stepwise consequent extractions with methanol and ethyl acetate and quantified by GC-negative chemical ionization-MS. It was found that the concentration of diazinon in the hair of exposed animals was dose dependent and was found to be 0.24 +/- 0.01 ng/mg (n = 5) and 0.53 +/- 0.05 ng/mg (n = 5) for the low and high dosage, respectively. The concentration in both dose groups was much higher than the corresponding rabbit hair (rabbits were exposed to the pesticide under similar experimental conditions) as previously reported. Our results strongly point to the possibility of using hair analysis for low-level exposure monitoring of diazinon.