Rapid Qualitative Analysis of 13 Precursor Chemicals by Fourier Transform Infrared Spectroscopy (FTIR)
LIU Cui-mei1*, HAN Yu1, JIA Wei1, FAN Ying-feng1, HUA Zhen-dong1, MIN Shun-geng2*
1. National Narcotics Laboratory, Drug Intelligence and Forensic Center of the Ministry of Public Security, Beijing 100193, China
2. College of Science, China Agricultural University, Beijing 100193, China
Abstract：For the first time, this study established an attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) method for fast qualitative analysis of 13 precursor chemicals. Due to the lack of qualitative identificationcriterion, FTIR has long just been used as a fast qualitative screening method. In order to expand its application in forensic sciences, two qualitative identification criteria of similarity coefficient method and characteristic peak method were investigated and compared based on the FTIR data of 152 seized ephedrine type samples. The range of the similarity coefficient values for ephedrine samples was 0.437～0.981. Generally speaking, sample with higher purity resulted in higher similarity coefficient value, but there is no linear relationship between the similarity coefficient value and the sample purity. Therefore, it is hard to select a threshold value. For characteristic peak method, eight peaks in the range of 2 500~650 cm-1 with relative high intensity and interference-free from common cutting agents were selected as the characteristic peaks. When the detection of all characteristic peaks was selected as the positive identification criteria, the positive detection rate for 152 ephedrine samples was 98.7%. Therefore, the characteristic peak method showed stronger specificity and wider application scope, and the results were reliable and accurate. This study established the characteristic peaks of 1-phenylpropan-2-one, 3,4-methylenedioxyphenylpropan-2-one, piperonal, N-acetylanthranilic acid, anthranilic acid, ephedrine, pseudoephedrine, 3-oxo-2-phenylbutanenitrile, 2-bromo-1-phenylpropan-1-one, N-phenethyl-4-piperidone, 4-anilino-N-phenethylpiperidine, 1-phenylpropan-1-one, and 1-chloro-N-methyl-1-phenylpropan-2-amine. The developed FTIR method that based on characteristic peak for precursor chemical identification provided a useful alternative to mass spectrometric method. It could significantly reduce the analysis time and cost, and greatly improve the identification efficiency.
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