Synchronized Inductive Desorption Electrospray Ionization Mass Spectrometry

摘要

Mass spectrometry (MS) plays an important role in chemical analysis which is currently being enhanced by the increasing demand for rapid trace analysis in the areas of public safety, forensics, food safety, and pharmaceutical quality assurance, amongst others. These demands constitute an impetus to simplify MS instrumentation and methodologies. This in turn has resulted in the development of miniaturized instrumentation and the invention of ambient ionization methods in which samples are examined without preparation in their native state. The ambient ionization methods include spray-based, plasma-based, and laser-assisted methods. Like other ambient methods, desorption electrospray ionization (DESI) has the advantages of simple instrumentation, rapid and sensitive analysis, and broad applicability. In situ mass spectrometry requires both portable instruments and simple ionization/sampling methods: In our laboratory, this requirement has been met by fitting the small ion trap based Mini 10 and 11 instruments with ambient ionization sources. The performance of the combined system is limited by the low pumping; speed of small mass spectrometers and the large nebulizing gas and solvent volumes that must be handled. This problem was addressed by the development of the discontinuous atmospheric pressure interface (DAPI). The DAPI interface is opened briefly to admit a bolus of ions, solvent vapor and gas, then closed while the neutrals are pumped away before the trapped ions are mass analyzed. The system operates well in spite of a duty cycle of just 1%.