LASER-DESORPTION IN A QUADRUPOLE ION-TRAP - MIXTURE ANALYSIS USING POSITIVE AND NEGATIVE-IONS

We demonstrate the generation of both negative and positive ions by la ser desorption directly within a quadrupole ion trap and the applicati on of this method to analyze complex samples containing compounds such as explosive residues, metal complexes, and polynuclear aromatic hydr ocarbons. In some cases the ability to rapidly switch between positive and negative ion modes provides sufficient specificity to distinguish different compounds of a mixture with a single stage of mass spectrom etry. In other experiments, we combine intensity variation studies wit h tandem mass spectrometry experiments and positive and negative ion d etection to further enhance specificity.