High pressure ion source combined with an in-axis ion trap mass spectrometer. 1. Instrumentation and applications

A new combination of a dual EI/CI ion source with a quadrupole ion trap mas s spectrometer has been realized in order to efficiently produce negative i ons in the reaction cell. Analysis of volatile compounds was performed unde r negative ion chemical ionization (NICI) during a reaction period where se lected reactant negative ions, previously produced in the external ion sour ce, were allowed to interact with molecules, introduced by hyphenated techn iques such as gas chromatography, The O-2(.-), CH3O-, and Cl- reactant ions were used in this study to ensure specific; ion/molecule interactions such as proton transfer, nucleophilic displacement, or charge exchange processe s, respectively leading to even-electron species, i.e., deprotonated [M -H] (-) molecules, diagnostic [M - R](-) ions, or odd-electron M-. molecular sp ecies, The reaction orientation depends on the thermochemistry of reactions within kinetic controls, First analytical results are presented here for t he trace-level detection of several contaminants under NICI/Cl- conditions. Phosphorus-containing compounds (malathion, ethyl parathion, and methyl pa rathion as representative for pesticides) and nitro-containing compounds (2 ,4,6-trinitrotoluene for explosive material) have been chosen in order to e xplore the analytical ability of this promising instrumental coupling.