Three-dimensional trace analysis: combination of gas chromatography, supersonic beam UV spectroscopy and time-of-flight mass spectrometry

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Abstract
We present a three-dimensional method for trace analysis by combining three different analytical techniques: gas chromatography, well-resolved 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 valve 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 improvement by two orders of magnitude seems realizable. Some further spectra of molecular isomers, such as PAHs of mass 252, chlorotoluenes or chloroanthracenes are shown as examples of how UV spectroscopy of even larger molecules allows isomer selective multiphoton ionization. The selectivity of this step is large enough so that time-consuming clean-up procedures of the sample are not necessary and medium resolution, but fast gas chromatography can be used.

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