Simultaneous GC-MS analysis of meta- and para-hydroxybenzoylecgonine and norbenzoylecgonine: a secondary method to corroborate cocaine ingestion using nonhydrolytic metabolites.

Positive benzoylecgonine (BZE) urinalysis results are sometimes challenged in legal and administrative proceedings on the grounds that the presence of BZE is due to the addition of cocaine to the urine sample with subsequent in vitro hydrolysis to BZE. Consequently, counsel for the respondent or defendant may move that an ecgonine methyl ester (EME) analysis be preformed because EME is presumed to be solely an in vivo cocaine metabolite. For these reasons, a sensitive and rapid gas chromatographic-mass spectrometric procedure was developed for the simultaneous analysis of m-hydroxybenzoylecgonine (m-OHBZE), p-hydroxybenzoylecgonine (p-OHBZE), and N-desmethyl benzoyl ecgonine (norBZE), all of which are cocaine metabolites believed to arise exclusively via in vivo metabolism. Analysis of human urine specimens previously reported positive for BZE using GC-MS at the Department of Defense cutoff of 100 ng/mL demonstrated that at least one of the three metabolites was present in 79 of the 82 specimens studied (96.3%). Thus, the simultaneous analysis of r-OHBZE, p-OHBZE, and norBZE could be used to substantiate that the presence of BZE in urine specimens is the result of cocaine ingestion. Additionally, the premise that EME is a "true" in vivo cocaine metabolite was investigated by assessing the stability of cocaine in unpreserved urine samples at several pHs ranging from 5.0 to 9.0.