On-Site Environmental Analysis by Membrane Inlet Mass Spectrometry

A membrane inlet mass spectrometric method for on-site environmental analysis in an advanced mobile analytical laboratory has been developed. A helium purge type of membrane inlet was used as a basis for the development of the method since it can be used in the GC/MS instrument available in the project without any modifications of the mass spectrometer. The custom-built membrane inlet can also be easily used with other types of quadrupole instruments. Results obtained show that many environmentally significant compounds can be measured directly from water samples at sub-parts-per-billion levels with response times of 1-2 min. The membrane inlet characterization studies show also that linear dynamic ranges of at least 4 orders of magnitude can be achieved. On-site analysis of contaminated ground-water samples shows that membrane inlet mass spectrometry (MIMS) is an excellent rapid analysis method for identification of pollutants. In addition, MIMS was shown to be a very good quantitation method over a wide concentration range. For example, a toluene concentration of 58 ppm and a trichloroethene concentration of 30 ppb were measured in one of the samples analyzed