污水中甲基苯丙胺干扰物N-甲基-2-苯基丙胺的结构解析

Structure Analysis of the Interfering Substance N-methyl-2-phenylpropan-1-amine of Methamphetamine in Wastewater

目的 解析污水样品中影响甲基苯丙胺分析结果的干扰物的化学结构。方法 综合利用GC-MS、液相色谱-四极杆飞行时间质谱(liquid chromatography-quadrupole time-of-flight mass spectrometry,LCQTOF-MS)对影响甲基苯丙胺分析结果的干扰物的质谱特征进行分析,推测其可能的结构,再使用液相色谱-三重四极杆质谱(liquid chromatography-triple quadrupole-mass spectrometry,LC-TQ-MS)进行对照品确证。结果 使用LC-QTOF-MS在电喷雾离子源正离子(positive electrospray ionization,ESI^(+))模式下分析,干扰物MS^(1)质谱的准分子离子质荷比与甲基苯丙胺完全一致,说明干扰物可能为甲基苯丙胺的同分异构体。不同碰撞能量(15 V、30V和45 V)下得到的MS^(2)质谱图也与甲基苯丙胺高度相似,推测干扰物中含有甲氨基和苄基。进一步使用GC-MS在电子轰击(electron impact,EI)电离模式下分析,干扰物质谱基峰的质荷比为44。经对照品添加分析,最终确认干扰物为N-甲基-2-苯基丙胺。结论 N-甲基-2-苯基丙胺的化学结构与甲基苯丙胺相似,在使用LC-TQ-MS对污水中痕量甲基苯丙胺进行检测时易产生干扰,实际分析中可借助色谱的保留时间进行区分。

Objective To analyze the chemical structure of the interfering substance that affects the result of methamphetamine analysis in wastewater.Methods A combination of GC-MS and liquid chromatographyquadrupole time-of-flight mass spectrometry(LC-QTOF-MS) was used to analyze the mass spectrum characteristics of the interfering substance that affects the result of methamphetamine analysis and to infer its possible structure.Liquid chromatography-triple quadrupole-mass spectrometry(LC-TQ-MS) was used to confirm the control material.Results Using LC-QTOF-MS in positive electrospray ionization(ESI^(+)) mode,the mass-to-charge ratio(m/z) of quasi-molecular ion in the MS^(1) mass spectrometry of interfering substance was identical to that of methamphetamine,indicating that the interfering substance was probably an isomer of methamphetamine.The MS^(2) mass spectra obtained at three collision energies of 15 V,30 V and 45 V were highly similar to methamphetamine,suggesting that the interfering substance contained methylamino and benzyl groups.Further analysis using GC-MS in electron impact(El)ionization mode showed that the base peak in the mass spectrum of the interfering substance was at m/z44.The interfering substance was confirmed to be N-methyl-2-phenylpropan-1-amine by compared with the standard reference.Conclusion The chemical structure of N-methy1-2-phenylpropan-1-amine is highly similar to methamphetamine,which is easy to cause interference for the detection of trace amounts of methamphetamine in wastewater using LC-TQ-MS.Therefore,in the actual analysis,the chromatographic retention time can be used to distinguish between N-methyl-2-phenylpropan-l-amine and methamphetamine.