A new method is described in which the mass spectrometer is an element specific detector for a gas chromatograph. The elements investigated in this study are F, Cl, Br, J, S and N, but the method might be applied to other elements as well. The molecules coming from the gas chromatograph are atomized in a microwave induced discharge, located in the interface between the gaschromatograph and the mass spectrometer. Unknown compounds containing specific elements can be detected and their retention times can be determined. The method is applied to samples of surface water, fat of a grebe and human adipose tissue for halogenated compounds. Unknown halogenated compounds were found. A number of them were identified in samples of surface water.