SOFT - TIAFT 1998 Poster Session 2 Wednesday October 7, 1998

S-C. Jane Tsai, Mahmoud ElSohly*, Tim Dubrovsky, Barbara Twarowska, Jim Towt and Sal J. Salamone

Roche Diagnostic Systems, Inc., 1080 US Highway 202, Somerville, NJ 08876, USA
ElSohly Laboratories, Inc., 5 Industrial Park Drive, Oxford, MS 38655, USA

The objective of this study was to investigate the effect of nitrite adulteration on the detection of five commonly abused drugs by immunoassay screening and GC-MS analysis. The drugs tested are cocaine metabolite (benzoylecgonine), morphine, 11-nor-D9-tetrahydrocan-nabinol-9-carboxylic acid (THC-COOH), amphetamine and phencyclidine. The immunoassays evaluated included the instrument-based Abuscreen ONLINE assays, the on-site Abuscreen ONTRAK assays, and the one-step ONTRAK TESTCUP-5 assay. Multianalyte standards containing various levels of drugs were used to test the influence of nitrite.

In the ONLINE immunoassays, the presence of up to 1.0 M of nitrite in the multianalyte standards had no significant effect on benzoylecgonine, morpnine and phencyclidine assays. With high concentrations of nitrite, ONLINE became more sensitive for amphetamine (detected more drug than what was expected) and less sensitive for THC-COOH (detected less drug than what was expected).

No effects of nitrite were observed on the results of the Abuscreen ONTRAK assays.

Similarly, no effects were observed on the absolute qualitative results of the TESTCUP-5 when testing with the nitrite adulterated standards. However, the intensities of the signals produced which indicate the negative test results were slightly lowered in the THC and phencyclidine assays.

The presence of 1.0 M of nitrite did not show dramatic interference with the GC-MS analysis of benzoylecgonine, morphine, amphetamine and phencyclidine. In contrast, the presence of as little as 0.03M of nitrite ion resulted in significant loss in the recovery of THC-COOH and its internal standard by GC-MS. The problem of nitrite adulteration could be alleviated by sodium bisulfite treatment even when the specimens were spiked with 1.0 M of nitrite ion. Although bisulfite treatment of nitrite containing samples resulted in the recovery of undegraded THC-COOH by GC-MS, the net recovery of THC-COOH depended on urinary pH and time and conditions of sample storage. The presence of nitrite that might arise from all possible natural sources did not interfere with the GC/MS analysis of THC-COOH.

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