红外光谱用于新精神活性物质快速定性分析

Rapid Qualitative Analysis of New Psychoactive Substances by Infrared Spectroscopy

分析了301种新精神活性物质(NPS)对照品的红外光谱,其中包括合成大麻素类100种、合成卡西酮类81种、苯乙胺类42种、色胺类9种、苯环利定类7种、哌嗪类5种、氨基茚类2种、其他类55种(含芬太尼类24种)。考察了红外光谱对NPS的整体区分能力以及红外光谱法定性鉴定NPS的判定依据。研究结果表明,红外光谱可实现对所有NPS的区分。对于97%的NPS具有较高的区分度,其中包括了烷基链上不同位置取代、苯环上不同位置取代、苯环上不同取代基取代等NPS结构类似物;某些差异仅为一个甲基或卤素原子的NPS类似物红外光谱相似度高,但也可实现区分。匹配度系数法是谱库检索最常用的方法,操作简单,但匹配度系数的计算结果由谱图质量、软件、算法等多个因素决定,因此难以确定普适性的阳性检出阈值。相比较于匹配度系数法,采用特征吸收峰法对NPS进行定性鉴定,结果更加准确可靠。一般情况下,在其对照品红外光谱图的2 500~650 cm^-1范围内选取8个相对强度较高的吸收峰作为特征吸收峰;针对某些结构类似物,需选取一些强度较低、但能将它与其类似物区分开的吸收峰作为特征吸收峰。只有当所有特征吸收峰均检出时,才能给出阳性检出结论。根据上述原则,确定了我国已列管168种NPS的特征吸收峰,并制定了公共安全行业标准《法庭科学疑似毒品中2-氟苯丙胺等168种新精神活性物质检验气相色谱-质谱、红外光谱和液相色谱法》。采用基于特征吸收峰的红外光谱法对NPS进行快速定性分析,将极大提高NPS定性检验的鉴定效率、降低鉴定成本。

In this study,the infrared spectra(IR)of 301 new psychoactive substances(NPS)reference substances,including 100 synthetic cannabinoids,81 synthetic cathinone,42 phenethylamines,9 tryptamines,5 piperazines,7 phencyclidine-type substances,2 aminoindanes,55 other types,were analyzed.The discriminant ability of IR for NPS,especially for NPS structural analogues,was investigated.The result showed that IR could well distinguish all kinds of NPS,even for some analogues with high spectrum similarity.IR has a high discrimination ability for 97%NPS,including alkyl chain-substituted regioisomers,ring-substituted regioisomers,different benzene ring disubstituted analogues,etc.The matching coefficient method is commonly used for spectral library search.The calculated matching coefficient value depends on several factors such as the quality of spectrum,software,algorithm,etc.,so it is difficult to determine a universal threshold for positive detection.Therefore,the matching coefficient method can be only used for preliminary screening.Compared with the matching coefficient method,the characteristic peak method is more accurate and reliable for qualitative identification.Generally,eight absorption peaks with relatively high intensity in the range of 2500~650 cm-1 are selected as characteristic peaks,but for some NPS structural analogues with similar spectra,it is necessary to select some low intensity but distinguishable peaks as characteristic absorption peaks.Only when all the characteristic absorption peaks are detected can the positive detection be concluded.According to this principle,characteristic absorption peaks of 168 regulated NPS were determined,and formed the IR method part of the industry standard“Forensic sciences—Examination methods for 168 new psychoactive substances including 2-FA in suspected drugs—GC-MS,IR and LC”.The rapid qualitative analysis of NPS by infrared spectroscopy based on a characteristic peak method will greatly improve the efficiency and reduce the cost of NPS qualitative identification analysis.