Estimation of the measurement uncertainty of methamphetamine and amphetamine in hair analysis.Forensic Sci Int. 2009 Mar 10; 185(1-3):59-66.FS
The measurement uncertainties (MUs) were estimated for the determination of methamphetamine (MA) and its main metabolite, amphetamine (AP) at the low concentrations (around the cut-off value of MA) in human hair according to the recommendations of the EURACHEM/CITAC Guide and "Guide to the expression of uncertainty in measurement (GUM)". MA and AP were extracted by agitating hair with 1% HCl in methanol, followed by derivatization and quantification using GC-MS. The major components contributing to their uncertainties were the amount of MA or AP in the test sample, the weight of the test sample and the method precision, based on the equation to calculate the mesurand from intermediate values. Consequently, the concentrations of MA and AP in the hair sample with their expanded uncertainties were 0.66+/-0.05 and 1.01+/-0.06 ng/mg, respectively, which were acceptable to support the successful application of the analytical method. The method precision and the weight of the hair sample gave the largest contribution to the overall combined uncertainties of MA and AP, for each.