REANALYSIS OF FORENSIC URINE SPECIMENS CONTAINING BENZOYLECGONINE ANDTHC-COOH

Drug testing laboratories are often requested to retest specimens that have tested positive. The reproducibility of analytical retest data f or delta-9-tetrahydrocannabinol-9-carboxylic acid (THE-COOH) and benzo ylecgonine in specimens that had previously been analyzed and then fro zen by the Navy Drug Screening Laboratory, Great Lakes is examined in this study. All specimens were tested by gas chromatography/mass spect rometry (GC/MS). Retest values generally showed a decrease in concentr ation but exhibited considerable variability. Eighty-five THE-COOH pos itive urine specimens stored frozen for 1 to 10 months (average 2.3 mo nths) declined an average of 25% (range, +30% to -80%) and 61 benzoyle cgonine positive urine specimens stored for 1 to 8 months (average 2.3 months) declined an average of 19% (ranged +20% to -100%) from initia l GC/MS test results. Drugs were found to partition into strata when f rozen in urine because of the thermodynamics of the freezing process. To assure a homogenous solution for repeat testing, specimens that hav e been frozen and thawed were gently mixed before analysis.