On-Line, In Situ Analysis with Membrane Introduction MS

Abstract

On-line in situ methods are not prominent for mass spectrometry (MS), although progress is expected. One approach to the development of such a capability is membrane introduction mass spectrometry (MIMS). MIMS provides capabilities that fit these requirements. The method employs flow injection analysis procedures for sample handling to provide an on-line capability, detects organic compounds in aqueous solution or in air, and offers relatively rapid response times (in the range of 0.5-5 min). Thus, there is the capability for continuous, on-line operation. In addition, internal or external standard solutions can provide quantitation. MIMS requires minimal operator intervention. Most strikingly, detection limits for VOCs are in the low part-per-trillion range (i.e., a few nanograms per liter). Compared with GC/MS, chemical speciation for MIMS is not as good, and the dynamic range, although several orders of magnitude, is not as great. On the other hand, the procedure is surprisingly free of matrix effects, and a single instrument is used for simultaneous, multicomponent analysis. MIMS performs best with relatively nonpolar and low molecular weight compounds, which can pass through silicone membranes. 20 refs., 4 figs., 1 tab.