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5361187 
Technical Report 
Stability of parathion metabolites in urine samples collected from poisoned individuals 
Comer, SW; Ruark, HE; Robbins, AL 
1976 
5 
618-625 
PESTAB. Serum cholinesterase values were correlated with O,O-diethylphosphorothioate (DETP), O,O-diethyl phosphate (DEP), and p-nitrophenol (PNP) levels in the urine of a child poisoned with parathion. Samples were collected initially, then on days 1-5 after administration of pralidoxime chloride. Portions of each sample were analyzed initially for each compound, and portions were stored in a deep freeze for up to six weeks. Urinary parathion dropped from 4 to less than 1 ppm within the first day after medical treatment, while the DEP levels declined from 0.5 to 0.1 ppm. The concentration of PNP dropped from 3.8 ppm to below 1 ppm the day after treatment, then rose to 1.5 ppm on the second day and declined thereafter. The concentrations of DETP and DEP and in the samples collected on various dates declined during frozen storage. A sample initially containing 4 ppm DETP contained approximately half this amount after 4 wk of storage. Frozen storage will lead to inaccurate results in the case of exposure to pesticides that metabolize to DETP. The decrease in DETP concentration of a stock solution was almost as fast when the solution was kept in frozen storage as at room temperature.