Determination of Methamphetamine · HCl Content in Methamphetamine · HCl and Ephedrine · HCl Mixtures by Improved Principal Component Score Analysis

Toshiyuki MITSUI

Scientific Investigation Laboratory, Aichi Police H.Q.; 2-1-1, Sannomaru, Naka-ku, Nagoya-shi 460-8502 Japan

The 13 samples, which contained 8 samples of accurate methamphetamine · HCl (Me) content and 5 samples of unknown Me content, were measured by FT-IR. The absorbance of each wavelength was divided by the absorbance of the 700.1 cm−1 wavelength and the 20 values from one sample were selected by Quantification IV. The correlation coefficient between each of the 20 values (categories) and Me content was calculated from the 8 samples of accurate Me content using a correlation equation. The 9 categories showed a correlation coefficient of over 0.900 and they were used for the determination of the Me content by the improved principal component score analysis (PCS2), principal component regression (PCR), partial least squares regression (PLS), and multiple regression analysis (MRA). The principal component analysis (PCS) using 20 categories and MRA using 9 or 20 categories were unsuitable for the determination of the Me content. The PCS2 method provided an accurate and precise quantitative analysis of the Me content.

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