Lockridge_2019_Chem.Biol.Interact__108788

Aqueous solutions of chlorpyrifos oxon are used to study the ability of chlorpyrifos oxon to catalyze protein crosslinking. Assays for protein crosslinking can avoid artifacts by using information on the stability of chlorpyrifos oxon in solution. We undertook to determine the half-life of chlorpyrifos oxon in aqueous solution because literature values do not exist. The rate of conversion of chlorpyrifos oxon to 3,5,6-trichloro-2-pyridinol was measured at 23 degrees C in 20mM TrisCl pH 8 and pH 9 by recording loss of absorbance at 290nm for chlorpyrifos oxon and increase in absorbance at 320nm for 3,5,6-trichloro-2-pyridinol. The half-life of chlorpyrifos oxon was 20.9 days at pH 8 and 6.7 days at pH 9. Literature reports for the stability of other organophosphorus toxicants were summarized because our current studies suggest that other organophosphorus toxicants are also crosslinking agents.