Morrison Kelsey A, Valenzuela Blandina R, Denis Elizabeth H, Nims Megan K, Atkinson David A, Clowers Brian H, Ewing Robert G
Pacific Northwest National Laboratory, Richland, WA, USA.
Analyst. 2020 Oct 21;145(20):6485-6492. doi: 10.1039/d0an00691b. Epub 2020 Aug 4.
Real-time, non-contact detection of illicit drugs is a desirable goal for the interdiction of these controlled substances, but the relatively low vapor pressures of such species present a challenge for trace vapor detection technologies. The introduction of atmospheric flow tube-mass spectrometry (AFT-MS), which has previously been demonstrated to detect gas-phase analytes at low parts-per-quadrillion levels for explosives and organophosphorus compounds, also enables the potential for non-contact drug detection. With AFT-MS, direct vapor detection of cocaine and methamphetamine from ∼5 μg residues at room temperature is demonstrated herein. Furthermore, thermal desorption of low- to sub-picogram levels of cocaine, methamphetamine, fentanyl, and heroin is observed via AFT-MS using a carrier flow rate of several L min of air. These low levels can permit non-contact sampling through collection of vapor, effectively preconcentrating the analyte before desorption and analysis. Quantitative evaluation of the thermal desorption approach has yielded limits of detection (LODs) on the order of 10 fg for cocaine and fentanyl, 100 fg for methamphetamine, and 1.6 pg for heroin. The LOD for heroin was lowered to 300 fg by using tributyl phosphate as a dopant to form a proton-bound heterodimer with heroin. When used with AFT-MS, the intentional formation of specific drug-dopant adducts has the potential to enhance detection limits and selectivity of additional drug species. Species that are prone to form adducts present a challenge to analysis, but that difficulty can be overcome by the intentional addition of a dopant. Molecules unlikely to form adducts will remain essentially unimpacted, but the adduct-forming species will interact with the dopant to compress the analyte signal into a single peak. This approach would be valuable in the application of non-contact screening for illicit substances via vapor collection followed by thermal desorption for analysis.
对非法药物进行实时、非接触式检测是拦截这些管制物质的一个理想目标，但此类物质相对较低的蒸气压给痕量蒸气检测技术带来了挑战。大气流动管质谱法（AFT-MS）的引入，此前已证明该方法能够检测出爆炸物和有机磷化合物中低至千万亿分之一水平的气相分析物，这也为非接触式毒品检测带来了可能性。本文展示了利用AFT-MS在室温下直接检测约5μg残留物中的可卡因和甲基苯丙胺蒸气。此外，通过AFT-MS在数升每分钟的空气载气流速下，观察到了低至亚皮克水平的可卡因、甲基苯丙胺、芬太尼和海洛因的热解吸。这些低水平允许通过收集蒸气进行非接触式采样，在解吸和分析之前有效地预浓缩分析物。对热解吸方法的定量评估得出，可卡因和芬太尼的检测限约为10fg，甲基苯丙胺为100fg，海洛因为1.6pg。通过使用磷酸三丁酯作为掺杂剂与海洛因形成质子结合异二聚体，海洛因的检测限降至300fg。当与AFT-MS一起使用时，有意形成特定的药物 - 掺杂剂加合物有可能提高对其他药物种类的检测限和选择性。易于形成加合物的物质对分析构成挑战，但通过有意添加掺杂剂可以克服这一困难。不太可能形成加合物的分子基本上不会受到影响，但形成加合物的物质会与掺杂剂相互作用，将分析物信号压缩成一个单峰。这种方法在通过蒸气收集进行非法物质的非接触式筛查，随后进行热解吸分析的应用中具有重要价值。
