Stability of toluene in blood: its forensic relevance.

Toluene is the chemical most frequently present in cases involving volatile solvents. Therefore, its stability is of prime forensic significance. Losses of toluene in three different blood standards stored at 24 degrees, 4 degrees, and -18 degrees C were studied at intervals of one, two, and seven weeks, and 34 and 46 months. The results were compared with previously published studies, and guidelines for the significant forensic analysis of toluene in blood are suggested. As previously cited, studies show that an accurate estimate of the initial toluene concentration is not possible, but its presence can be documented with an ion trap detector after 46 months if the initial concentration was above 0.04 mg/dL, even in specimens stored at 4 degrees C in a Vacutainer (90% filled) without preservative. If the specimen is collected in a Vacutainer at approximately 90% capacity and stored at 24 degrees C or below, up to 25% loss of toluene after one week can be expected.