Thermal stability of organophosphorus pesticide triazophos and its relevance in the assessment of risk to the consumer of triazophos residues in food.

The degradation of triazophos in aqueous solutions was monitored at 205 and 254 nm after separation using high-performance liquid chromatography. An ODS column was used with a mobile phase of 60% acetonitrile and 0.04% phosphoric acid at a flow rate of 1.4 cm(3) min(-)(1). When dissolved in distilled water, approximately 30% of the original triazophos was detected. The effect of heating time and temperature on a 0.5 mg dm(-3) standard was investigated. Over a 150 min period at 100 degrees C the peak area detected for the standard decreased by 58.67 +/- 6.19 and 65.03 +/- 4.61% when measured at 254 and 205 nm, respectively. The precision of the absorbance detected at 205 and 254 nm was 3.54 +/- 2.8 and 3.86 +/- 3.9%, respectively. There was a significant difference (P = 0.10) between the precision of the results obtained at each wavelength. The t(calcd) value was -2.236 and the t(crit) value was 1.94. The most sensitive wavelength was 205 nm. A 54% difference in the gradients of the calibration graphs obtained at each wavelength was observed. The results suggest that approximately 72% of triazophos is degraded during a 20 min cooking period at 100 degrees C, due to ambient and elevated temperature hydrolysis. Therefore, the dose to the consumer of triazophos residues in cooked food is likely to be approximately 72% lower than in the raw food, with a concomitant reduction in toxicological risk.