基于非目标筛查技术的甲基苯丙胺合成路线分析

郑晓雨, 赵彦彪, 闻武, 郑珲

刑事技术 ›› 2023, Vol. 48 ›› Issue (6) : 577-583. DOI: 10.16467/j.1008-3650.2023.0020
论著

基于非目标筛查技术的甲基苯丙胺合成路线分析

作者信息 +

Non-Targeted Profiling of Methamphetamine in China

Author information +
History +

摘要

本文基于气相色谱-质谱联用和多变量分析,建立对样品中痕量杂质成分的非目标筛查技术,实现制毒合成工艺路线推断。优化甲基苯丙胺中杂质成分的气相色谱-质谱联用分析条件,通过主成分分析(PCA)、正交偏最小二乘法判别分析(OPLS-DA)和层次聚类法(HCA)等多变量分析方法对已知合成工艺路线的甲基苯丙胺进行分类处理,进而对未知缴获样品进行关联性分析及合成工艺路线推断。结果显示,本方法可在缺少杂质成分标准物质的情况下,实现对缴获甲基苯丙胺关联性分析和合成工艺路线推断。所建立的非目标筛查技术具有操作简单、可靠性高、无需杂质的标准物质等优势,可为打击涉甲基苯丙胺犯罪提供情报支撑。

Abstract

Based on gas chromatography mass spectrometry and multivariate analysis, non-targeted profiling of methamphetamine in China was established to deduce the synthetic routes. After optimizing analysis condition with gas chromatography mass spectrometry, following appropriate examination of all the peaks, 32 impurities were selected as the specific components in seized methamphetamine samples. Unsupervised (principal component analysis, PCA; hierarchical cluster analysis, HCA) and supervised (orthogonal projections to latent structures-DA, OPLS-DA) techniques were employed for classifying the 190 MA seizures. The results of PCA, HCA and OPLS-DA were in good agreement and showed a good tool for analyzing seizures correlation and synthesis routes. The established non-targeted screening technology has the advantage of simple operation, high reliability, not needing standard materials of impurities and can provide informative support to crack down the methamphetamine-related crime.

关键词

毒品 / 气相色谱-质谱联用 / 非目标筛查 / 甲基苯丙胺 / 合成路线

Key words

illicit drug / gas chromatography mass spectrometry (GC-MS) / non-targeted screening / methamphetamine / synthesis routes

引用本文

导出引用
郑晓雨 , 赵彦彪 , 闻武 , 郑珲. 基于非目标筛查技术的甲基苯丙胺合成路线分析. 刑事技术. 2023, 48(6): 577-583 https://doi.org/10.16467/j.1008-3650.2023.0020
ZHENG Xiaoyu , ZHAO Yanbiao , WEN Wu , ZHENG Hui. Non-Targeted Profiling of Methamphetamine in China. Forensic Science and Technology. 2023, 48(6): 577-583 https://doi.org/10.16467/j.1008-3650.2023.0020
甲基苯丙胺结构简单,其合成路线较多,主要合成原料包括麻黄碱、伪麻黄碱和苯基丙酮(P2P)等[1]。以麻黄碱为原料,用氢碘酸还原合成制造甲基苯丙胺,被称为Nagai法[2]。用碘和红磷生成氢碘酸再还原则被称为Moscow法。利用液氨、锂或钠等代替氢碘酸,被称为Birch还原法。制毒者将一步还原法演变为两步还原法,即将麻黄碱用氯化亚砜、三氯氧磷或高氯酸等氧化成卤代麻黄碱,再经氢/钯还原催化加氢生成甲基苯丙胺,分别被称为Emde法和Hypo法[3]。以上方法中主要原料麻黄碱的传统来源主要包括含麻复方制剂提取和麻黄草提取等。随着麻黄碱被严格管控,制毒者选择化学合成或半合成麻黄碱或者绕开麻黄碱选择其他路径,如以苯丙酮、溴和甲胺为原料,用氢和雷尼镍还原制造甲卡西酮,进一步反应制备得到麻黄碱。P2P与甲胺经还原胺化反应得到甲基苯丙胺被称为Reduction Amination法。P2P与N-甲基甲酰胺作用经酸性条件下水解得到甲基苯丙胺,称为Leuckart法[4]。此外,制毒者利用硝基苯乙烯、苯甲醛、苯乙酸、苯乙腈、氯化苄等原料开发新型途径合成P2P。为制造得到具有更高效力的d-甲基苯丙胺,制毒者往往选用l-麻黄碱或d-伪麻黄碱为原料。而采用苯丙酮等合成麻黄碱再制造甲基苯丙胺或由P2P合成制造甲基苯丙胺,如不经过手性分离则得到外消旋甲基苯丙胺[5]
甲基苯丙胺作为化学合成产物,在最终产品中或多或少存在合成原料、中间产物以及杂质成分等。欧盟于2004年发起苯丙胺类兴奋剂分析方法合作协调项目[6],美国在过去二十年持续开展了甲基苯丙胺成分剖析项目[7],研究了甲基苯丙胺在毒品质量及合成路线的演变趋势。通过样品中(1S,2S)-1-甲基氨基-1-苯基-2-氯丙烷[8]或1-苄基-3-甲基萘[9]等特征杂质成分可实现合成路线推断,但通过单一特征标记物确定合成路线存在一定的误判风险,如曾被认为是Leukart合成路线特征标记物的N-甲酰胺甲基苯丙胺后被证实也存在于其他路线合成的样品中[10]。此外,也无法提供批次关联等信息。通过应用主成分分析(PCA)、层次聚类分析(HCA)、正交偏最小二乘判别分析(OPLS-DA)等[11-12]统计技术对多个杂质数据进行化学计量分析,可对获取有关合成信息提供极大帮助。Dayrit等[13]通过气相色谱-质谱联用对甲基苯丙胺中痕量杂质的峰面积进行分组聚类分析,成功区分合成路线。Cui等[14]选取20种特征杂质作为分析变量,通过优化数据预处理方法和检验模型,以HCA确定可卡因样本之间的关联性,为有关机构提供执法依据。Segawa等[15]则利用多元变量分析,建立基于空间异构体比例的分析方法,应用于44份甲基苯丙胺样品的合成信息推断。本文通过气相色谱质谱技术,优化杂质成分分析条件,建立实际缴获样品的合成路线推断模型,得到较好的聚类一致性且与近年来实际情况吻合,可为禁毒情报研判提供有益支撑。

1 材料与方法

1.1 仪器、试剂与材料

气相色谱-质谱联用仪(安捷伦 7890A-5975C),分析天平(梅特勒,分度值0.1 mg)。
甲基苯丙胺样品为2014—2022年缴获的190份检材。
正己烷、氯仿(均为色谱纯,Fisher),盐酸、氢氧化钠、三羟甲基氨基甲烷(Tris)、甲苯、乙酸乙酯、苯(以上试剂均为分析纯,购自国药集团),超纯水由 Milli-Q 超纯水机(美国 Millipore 公司)制取。

1.2 样品前处理

三羟甲基氨基甲烷缓冲液配制:配制1 mol/L的三羟甲基氨基甲烷溶液,用浓盐酸调节pH至8.0。
将缴获的甲基苯丙胺样品研磨均匀后,称取约200 mg于玻璃离心管中,加入4 mL Tris缓冲液,超声溶解,加入0.5 mL有机溶剂后振荡30 min,5 000 r/min离心5 min分层,吸取上层有机相待检。

1.3 分析条件

色谱柱:DB-35MS毛细管柱 30 m×0.32 mm×0.25 μm;柱温:80 ℃保持1 min,6 ℃/min升温至300 ℃,保持5 min,检测器温度280 ℃,进样口温度250 ℃,进样量1 μL,不分流进样,在10.7~11.2 min内检测器关闭,溶剂延迟3.5 min;EI电离源;电离能量70 eV;四级杆温度150 ℃;离子源温度230 ℃;全扫描模式,扫描范围35~400 amu。

1.4 数据处理

参照《疑似毒品中甲基苯丙胺的气相色谱、高效液相色谱和气相色谱-质谱检验方法》(GB/T 29636-2013)中关于阳性结果判定依据,锁定气相色谱总离子流图(TIC)中杂质成分的保留时间及3个离子碎片丰度比允差范围。重复3次进样,取样本中目标峰保留时间的平均值,允许误差为0.1 min。各离子丰度比相对偏差不超过表1范围。确定最小峰面积、阈值角等积分条件,以峰面积为分析对象,分别采用主成分分析(PCA)、层次聚类分析(HCA)和正交偏最小二乘法-判别分析(OPLS-DA)进行分析。
表1 特征离子丰度比的最大允许相对偏差范围

Table 1 Acceptable maximum RSD (relative standard deviation) of ratios of characteristic ions abundance

特征离子
丰度比
>50% >20%~50% >10%~20% ≤10%
最大允差 ±10% ±15% ±20% ±50%

2 结果与讨论

2.1 气相色谱-质谱联用条件的优化

用浓盐酸调节萃取溶液的pH,以甲苯萃取后,经气相色谱-质谱联用分析如图1所示。不同杂质成分在不同萃取pH下的萃取效率具有明显差异。为便于分析,选取pH为1、4、8、11时进行对比。对于保留时间为21.4 min的组分中的杂质峰, pH=1时峰强度明显;RT=24.4 min的杂质峰,在pH=11时峰强度达到最大;RT=27.4 min的杂质峰,pH在1、4、8时峰强变化不大,而pH=11时杂质峰几乎消失。此外,随着pH值增大,各杂质成分的出峰时间均出现延迟。通过比较样品在不同pH下的杂质峰个数,选定萃取pH为8。
图1 不同萃取pH下的杂质峰

Fig.1 Peaks of impurities under different pH

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萃取过程在于甲基苯丙胺和杂质成分在不同溶剂间的竞争分配,有机溶剂的极性对杂质成分的萃取具有明显影响。由图2可见,由于甲醇具较强极性, 对甲基苯丙胺和杂质成分均具有极高的萃取效率,导致甲基苯丙胺出现过载现象,且未能对杂质进行有效分离。苯和甲苯具有更佳的萃取表现,同时考虑到溶剂毒性,本实验选择甲苯为有机萃取溶剂。
图2 不同有机溶剂提取后的色谱图

Fig.2 TIC spectrum of GC-MS of methamphetamine samples extracted by different solvents

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为保证杂质峰达到最佳分离,对气相色谱条件进行优化,如图3所示。锁定保留时间偏差为0.1 min,并对各杂质峰按照出峰保留时间和三对最强碎片离子的丰度比进行标记。对不同合成路线的甲基苯丙胺样本进行分析,选取32个峰作为后续分析对象。通过气相色谱-质谱联用的峰纯度分析,可知32个杂质峰均为单一化合物。
图3 优化条件下的样品色谱图

Fig.3 TIC spectrum of GC-MS of methamphetamine sample under the optimized condition

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2.2 非目标筛查方法

对60份已知合成路线的甲基苯丙胺样本进行分析,其中包括:1)以(伪)麻黄碱、碘、红磷为原料的Nagai、Moscow方法;2)以(伪)麻黄碱为原料采用催化加氢的Emde方法;3)以P2P为原料的Leuckart或还原胺化法;4)以苯乙腈为原料合成P2P再制造甲基苯丙胺的方法。
积分计算以上杂质的峰面积。利用SIMCA17对所得数据按照7-fold交叉验证进行主成分处理。研究转置、峰面积归一化、峰面积开平方、峰面积开四次根等数据预处理及UV、Par等距离模型计算方式对主成分分析结果的影响,计算组间和组内比值,取比值最大为最优化处理方式[16],如图4所示,R2X和Q2均具有正相关系数。通过主成分分析散点图分析可知,不同制毒路线的甲基苯丙胺可以实现较好的分离,且对应的主要杂质成分如图4所示。
图4 优化的甲基苯丙胺主成分分析结果

Fig.4 Principal component analysis for seized methamphetamine samples

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以还原胺化法和碘红磷法为例,利用OPLS-DA对两种方法合成的甲基苯丙胺进行研究。如图5所示,两种样品得到很好的分离,为验证是否存在过度拟合,随机分组200次的置换检验,所有R2和Q2左边的点都低于右边的点,R2和Q2的回归线斜率均为正。按照VIP>1且P<0.05和S-Plot两端影响因素,分析可得两种制毒工艺的特征识别物。RT=9.24min处对应峰经分析为1,2-二甲基-3-苯基氮丙啶。
图5 基于OPLS-DA的多元变量分析结果与非目标筛查的特征标记物

Fig.5 Route specific markers from OPLS-DA based multivariate analysis and non-targeted screening

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在制造甲基苯丙胺常见路线中,该物质主要形成可能如下:碘代(伪)麻黄碱的碘被邻近氮亲核攻击取代成顺或反式1,2-二甲基-3-苯基氮丙啶,或麻黄碱的羟基通过分子内亲核取代或分子间亲核取代反应被氯取代,成环形成反式-1,2-二甲基-3-苯基氮杂环啶。在反应过程中可还原生成甲基苯丙胺也可能水解生成P2P,并进一步形成1-苄基-3-甲基萘和1,3-二甲基-2-苯基萘。这意味着,杂质中出现少量P2P并能说明该缴获物的原料为P2P,同时1-苄基-3-甲基萘和1,3-二甲基-2-苯基萘在其他工艺路线制造的甲基苯丙胺中均未发现,因此一般认为其可以作为以(伪)麻黄碱为原料制造甲基苯丙胺的特征识别物。这进一步说明了项目组所建立数据模型分析制毒工艺路线特征识别物的准确性。
利用SPSS软件,采用层次聚类法对60个已知样品进行聚类分析,如图6所示。各样品之间分类准确,不存在分类交叉或错误分类。在此基础上,对近年来缴获的130份甲基苯丙胺样品进行层次聚类分析,从而实现对样品合成路线的研判推断。可以看出,其中69份疑似以麻黄碱伪原料,通过催化加氢方法合成,这与实际掌握情况基本一致。结合样品缴获年限,分析可知当前我国甲基苯丙胺合成工艺路线的变化趋势,从而为精准管控制毒原料、发现新型潜在制毒原料和工艺提供科技支撑。
图6 基于层次聚类法模型的样品合成路线推断

Fig.6 Synthesis routes inferred by cluster analysis models

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3 结论

通过优化前处理、气相色谱-质谱联用分析条件实现对甲基苯丙胺中杂质成分的分离和筛选,利用主成分分析(PCA)、正交偏最小二乘法判别分析(OPLS-DA)和层次聚类法(HCA)等多变量分析方法建立不同样本的聚类分析模型,并对样品合成路线进行研判推断。经实际样品验证可知,该模型分类准确,可服务于打击毒品犯罪工作,防止毒品走私贩运。

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Methamphetamine hydrochloride is one of the most widely used illicit drugs in the Philippines. In this study, we describe the application of cluster analysis of trace impurities in the profiling of the seized methamphetamine drug samples. Thirty milligrams of a homogenized drug sample were dissolved in 1 mL of pH 10.5 buffer solution and extracted with ethyl acetate containing three internal standards. The trace impurities were identified using gas chromatography-mass spectrometry (GC-MS) and quantified by gas chromatography with a flame ionization detector (GC-FID). Following previously reported methodologies, 30 impurity peaks were selected from the GC-FID chromatograms. The peak areas and retention times were referenced to the internal standards. The peak areas of the selected peaks were then grouped for cluster analysis. In order to check for consistency of clustering, two further cluster analyses were performed using 40 and 50 impurity peaks. Changes in clustering were observed in going from 30 to 40 impurity peaks, while analyses using 40 and 50 impurity peaks gave similar results. Thus, for the seized drug samples used in this study, cluster analysis using at least 40 impurity peaks showed better consistency of clustering as compared to analysis using 30 peaks only. Ten of the impurity peaks were identified, of which four were identified for the first time in methamphetamine drug samples. These are p-bromotoluene, N-benzyl amphetamine, N-ethyl amphetamine, and N-ethyl methamphetamine. The presence of phenyl-2-propanone (P2P), N,N-dimethyl amphetamine, and N-formyl amphetamine is indicative that these casework samples were synthesized using the Leuckart method.
[14]
CUI X, WANG R, LIAN R. et al. Correlation analysis between cocaine samples seized in China by the rapid detection of organic impurities using direct analysis in real time coupled with high-resolution mass spectrometry[J]. International Journal of Mass Spectrometry, 2019, 444: 116188.
[15]
SEGAWA H, OKADA Y, YAMAMURO T. et al. Stereoselective analysis of ephedrine and its stereoisomers as impurities and/or by-products in seized methamphetamine by supercritical fluid chromatography/tandem mass spectrometry[J]. Forensic Science International, 2021, 318: 110591.
[16]
SHIN D W, KO B J, CHEONG J C. et al. Impurity profiling and chemometric analysis of methamphetamine seizures in Korea[J]. Analytical Science and Technology, 2020, 33(2): 98-107.

基金

国家重点研发计划国家质量基础设施体系专项课题(2021YFF0602501)
国家自然科学基金青年基金项目(21806022)
中央级公益性科研院所基本科研业务费专项资金项目(2018JB042)

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