Hydrolytic products and kinetics of triazophos in buffered and alkaline solutions with different values of pH

The hydrolysis of triazophos was studied in buffered solutions in the range of pH 4-10 and in sodium hydroxide solutions with pH values up to 12. The results showed that the degradation of triazophos in the above solutions followed simple pseudo-first-order kinetics. At 35 degrees C, the rate constants in buffered solutions ranged from 0.0222 d(-1) at pH 4 to 0.5357 d(-1) at pH 10, and increased to 0.6251 h(-1) in 0.01 mol/L sodium hydroxide solution. The results also indicated that the base-catalysis was more important than acid-catalysis in the hydrolysis of triazophos. On the basis of the Arrhenius plot, the calculated activation energy (E(a)) and the frequency factor (A) for the hydrolysis of triazophos in buffered solution of pH 10 were 78.6 kJ/mol and 1.13 x 10(13) d(-1), respectively. Hydrolytic products of triazophos in buffered solutions of pH 4 and 10, as well as in sodium hydroxide solution of pH 11, were identified as their corresponding trimethylsilyl derivatives with a gas chromatography-mass spectrometer (GC-MS). The possible hydrolytic pathways of triazophos were also proposed.