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Interlaboratory Studies on the Analysis of Hair for Drugs of Abuse: Results From Three Exercises (From Hair Testing for Drugs of Abuse: International Research on Standards and Technology, P 133-147, Edward J Cone, et al, eds.)

NCJ Number
Date Published
August 1996
15 pages
As part of a program to develop methods and standards to support hair testing for drugs of abuse, the National Institute of Standards and Technology invited interested laboratories to participate in interlaboratory comparison studies to determine how well drugs in hair could be detected and quantified.
Several laboratories participated in three experiments involving the analysis of cocaine, benzoylecgonine, morphine, and codeine. Hair samples included drug-free hair and hair in which drugs had been fortified by soaking hair in drug solutions. The three experiments demonstrated that most laboratories could reliably detect the presence of target compounds in hair. Not surprisingly, laboratory performance improved with increasing drug concentration. Cocaine and benzoylecgonine were the most frequently missed substances in all experiments. The incidence of false positives was low, and many positive levels reported on negative challenges were low enough to be below likely cutoff levels. None of the experiments demonstrated the superiority of a particular analysis method. Variations in hair pretreatment, extract times, and extraction temperatures all affected results. Acid extraction, methanol extraction, and enzyme digestion generally performed about equally well. Evidence from one experiment showed that enzyme digestion may have performed slightly better than acid extraction, except when long extractions were used. Variations in procedures for isolating analytes from the hair matrix were probably responsible for most of the scatter observed in quantitative results. 2 references and 3 tables

Date Published: August 1, 1996