Coy Stephen L, Krylov Evgeny V, Nazarov Erkinjon G, Fornace Albert J, Kidd Richard D
Planetary Chemistry and Astrobiology, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099.
Int J Ion Mobil Spectrom. 2013 Sep;16(3):217-227. doi: 10.1007/s12127-013-0135-3.
Electrospray ionization (ESI) is an important tool in chemical and biochemical survey and targeted analysis in many applications. For chemical detection and identification electrospray is usually used with mass spectrometry (MS). However, for screening and monitoring of chemicals of interest in light, low power field-deployable instrumentation, an alternative detection technology with chemical selectivity would be highly useful, especially since small, lightweight, chip-based gas and liquid chromatographic technologies are being developed. Our initial list of applications requiring portable instruments includes chemical surveys on Mars, medical diagnostics based on metabolites in biological samples, and water quality analysis. In this report, we evaluate ESI-Differential Mobility Spectrometry (DMS) as a compact, low-power alternative to MS detection. Use of DMS for chemically-selective detection of ESI suffers in comparison with mass spectrometry because portable MS peak capacity is greater than that of DMS by 10X or more, but the development of light, fast chip chromatography offers compensating resolution. Standalone DMS provides the chemical selectivity familiar from DMS-MS publications, and exploits the sensitivity of ion detection. We find that sub-microliter-per-minute flows and a correctly-designed interface prepare a desolvated ion stream that enables DMS to act as an effective ion filter. Results for a several small organic biomarkers and metabolites, including citric acid, azelaic acid, n-hexanoylglycine, thymidine, and caffeine, as well as compounds such as dinitrotoluene and others, have been characterized and demonstrate selective detection. Water-quality-related halogen-containing anions, fluoride through bromate, contained in liquid samples are also isolated by DMS. A reaction-chamber interface is highlighted as most practical for portable ESI-DMS instrumentation.
电喷雾电离（ESI）是化学和生化检测以及许多应用中靶向分析的重要工具。在化学检测和鉴定中，电喷雾通常与质谱（MS）联用。然而，对于在轻便、低功率的现场可部署仪器中筛选和监测感兴趣的化学物质而言，一种具有化学选择性的替代检测技术将非常有用，特别是因为小型、轻便的基于芯片的气相和液相色谱技术正在不断发展。我们最初列出的需要便携式仪器的应用包括火星上的化学探测、基于生物样品中代谢物的医学诊断以及水质分析。在本报告中，我们评估了ESI-差分迁移谱（DMS）作为一种紧凑、低功率的替代MS检测的技术。与质谱相比，使用DMS进行ESI的化学选择性检测存在不足，因为便携式MS的峰容量比DMS大10倍或更多，但轻便、快速的芯片色谱的发展提供了补偿性分辨率。独立的DMS提供了DMS-MS出版物中常见的化学选择性，并利用了离子检测的灵敏度。我们发现，每分钟亚微升的流速和正确设计的接口可制备出脱溶剂化离子流，使DMS能够作为一种有效的离子过滤器。对几种小的有机生物标志物和代谢物（包括柠檬酸、壬二酸、正己酰甘氨酸、胸苷和咖啡因）以及二硝基甲苯等化合物的检测结果已得到表征，并证明了其选择性检测能力。液体样品中与水质相关含卤素阴离子（从氟化物到溴酸盐）也可通过DMS分离。对于便携式ESI-DMS仪器而言，反应室接口被认为是最实用的。
