TLC analysis of urine for benzoylecgonine and norpropoxyphene

A thin-layer chromatography (TLC) procedure has been developed for the analysis of urine samples for benzoylecgonine and norpropoxyphene, the major metabolites of cocaine and propoxyphene, respectively. Urine is made slightly acidic and methylated with dimethyl sulfate to convert the difficult-to-extract benzoylecgonine back into the much more readily extractable cocaine. The urine is then chilled, made basic, and extracted with chloroform/isopropanol. The organic layer containing the cocaine and norpropoxyphene is separated and evaporated to dryness. The residue is reconstituted and spotted on a TLC plate which is developed in hexane:chloroform:diethylamine (80:10:10) which separates the two substances without interference from other drugs, metabolites, and urinary substances. The two substances are visualized with acidified iodoplatinate spray and can be detected down to levels of 2.0 microgram/mL for benzoylecgonine and 1.0 microgram/mL for norpropoxyphene.