| Abstract
| - The crucial step in current concepts to interface isotoperatio mass spectrometry (IRMS) to gas chromatography(GC) is efficient solvent removal. This is due to theessential postcolumn conversion of the analytes intosimple gases, which is performed by either combustionor pyrolysis. The capacity of this step merely suffices toconvert the analytes. Already small amounts of solventpresent in the respective furnace can cause severe damage. In conventional GC/IRMS interfaces, the solvent isremoved after passage of the GC column. Either back-flushing or flow diversion is employed for this purpose.Both techniques necessitate the use of numerous components such as unions, tee pieces, valves, and capillaryconnections. Often this results in significant deteriorationof the chromatographic resolution. In contrast, accurateGC/IRMS measurements require baseline separation ofadjacent peaks. Moreover, maintenance of conventionalinterfaces may be tedious and time consuming, mostlybecause the numerous connections are prone to leakage.In order to avoid these drawbacks, we propose a conceptto efficiently remove the solvent before passage of the GCcolumn. It is based on the use of a cooled injection systemoperated in solvent vent mode, where the solvent elimination is supported by an auxiliary pump. Most unions andtee pieces thus can be removed. The chromatographicresolution is considerably enhanced. In particular, analysis of high-boiling and polar compounds can be improved.At the same time, the maintenance of the system issignificantly facilitated. Under the chosen conditions,partial losses of low-boiling analytes during solvent elimination were not associated with significant isotope fractionation.
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