A membrane inlet mass spectrometric method for on-site environmental a
nalysis in an advanced mobile analytical laboratory has been developed
, A helium purge type of membrane inlet was used as a basis for the de
velopment of the method since it can be used in the GC/MS instrument a
vailable in the project without any modifications of the mass spectrom
eter. The custom-built membrane inlet can also be easily used with oth
er types of quadrupole instruments. Results obtained show that many en
vironmentally significant compounds can be measured directly from wate
r samples at sub-parts-per-billion levels with response times of 1-2 m
in. The membrane inlet characterization studies show also that linear
dynamic ranges of at least 4 orders of magnitude can be achieved, On-s
ite analysis of contaminated groundwater samples shows that membrane i
nlet mass spectrometry (MIMS) is an excellent rapid analysis method fo
r identification of pollutants. In addition, MIMS was shown to be a ve
ry good quantitation method over a wide concentration range, For examp
le, a toluene concentration of 58 ppm and a trichloroethene concentrat
ion of 30 ppb were measured in one of the samples analyzed.