Benzoylecgonine, 11-nor-delta 9-tetrahydrocannabinol-9-carboxylic acid (THC-acid), phencyclidine, codeine, morphine, amphetamine, methamphetamine, and lysergic acid diethylamide were dissolved in urine, stored frozen in plastic tubes at -16 to -18 degrees C, defrosted, transferred to other tubes, and analyzed by gas chromatography/mass spectrometry (GC/MS); no significant loss of compound was observed, except for THC-acid, which showed an average loss of 11%, ranging from 0 to 34% of the total concentration. The loss is attributed to the decrease in solubility of the compound and to adherence to the side of the container during freezing.
No takes yet. Share an insight, caveat, or question.
Paul et al. (1993) studied this question.
Synapse has enriched 3 closely related papers on similar clinical questions. Consider them for comparative context: