Stability of Drugs of Abuse in Urine Samples Stored at −20°C

American Medical Laboratories, Chantilly, VA 22021.
Journal of analytical toxicology (Impact Factor: 2.86). 11/1994; 18(7):391-6. DOI: 10.1093/jat/18.7.391
Source: PubMed


Isolated studies of the stability of individual drugs of abuse have been reported. However, few have evaluated stability in
frozen urine samples stored for 12 months. We have determined the stability of 11-nor-9-carboxy-Δ9-tetrahydrocannabinol (9-COOH-THC), amphetamine, methamphetamine, morphine, codeine, cocaine, benzoylecgonine, and phencyclidine
in 236 physiological urine samples. Following the initial quantitative analysis, the samples were stored at −20°C for 12 months
and then reanalyzed. All drug concentrations were determined by gas chromatographic-mass spectrometric methods with cutoff
concenlrations of 5 ng/mL for 9-COOH-THC and phencyclidine and 100 ng/mL for each of the other drugs. The average change in
the concentrations of these drugs following this long-term storage was not exlensive except for an average change of −37%
in cocaine concentrations.

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