An enzyme based assay for differential determination of coumaphos and potasan in cattle dips

An enzyme-based assay was developed to monitor the levels of the organophos phate acaricide coumaphos and potasan, a metabolite formed by reductive dec hlorination in cattle dipping solutions. The assay relies on the differenti al rates of hydrolysis of coumaphos and potasan by the enzyme parathion hyd rolase (organophosphorous anhydrase [EC 3.1.8.1]). Hydrolysis of coumaphos and potasan yields the fluorescent products chlorferon and 4-methylumbellif erone, respectively. By altering the reaction conditions and measuring the formation of fluorescent compounds in two parallel reactions (one reaction for potasan hydrolysis, one reaction for hydrolysis of potasan and coumapho s), it was possible to measure both coumaphos and potasan in samples from c attle dipping vats and from a bioreactor used for digestion of coumaphos-co ntaining wastes. This sensitive and reliable assay would be suited for use in remote field sites where more conventional chemical analysis is difficul t to obtain.