3-DIMENSIONAL TRACE ANALYSIS - COMBINATION OF GAS-CHROMATOGRAPHY, SUPERSONIC BEAM UV SPECTROSCOPY AND TIME-OF-FLIGHT MASS-SPECTROMETRY

We present a three-dimensional method for trace analysis by combining three different analytical techniques: gas chromatography, well-resolv ed gas-phase UV spectroscopy of cold molecules and time-of-flight mass spectrometry with a laser ionization source. The interface is a newly developed pulsed valve, which acts as a GC-MS coupling as well as a v alve for the pulsed supersonic beam. We prove that the selectivity of both the gas chromatography and the UV spectroscopy is preserved. The preliminary sensitivity is better than 500 fg for toluene, an improvem ent by two orders of magnitude seems realizable. Some further spectra of molecular isomers, such as PAHs of mass 252, chlorotoluenes or chlo roanthracenes are shown as examples of how UV spectroscopy of even lar ger molecules allows isomer selective multiphoton ionization. The sele ctivity of this step is large enough so that time-consuming clean-up p rocedures of the sample are not necessary and medium resolution, but f ast gas chromatography can be used.