Miniature Combustion Reactors to Increase Sensitivity and Selectivity, and to Facilitate GCxGC for Compound-specific Isotope Analysis (CSIA)

The online combustion of analytes between gas chromatography and isotope ratio mass spectrometry (GC-C-IRMS) has enabled compound-specific isotope analysis (CSIA) for various applications, such as assessment of environmental contaminants or doping in sports. However, CSIA is challenged by the need for complete peak separation and the need for improved sensitivity. Comprehensive gas chromatography (GCxGC) could deliver a breakthrough, but hinges on developing robust miniaturized online combustion tubes. They must offer sufficient oxidation capacity and catalytic surface area to accomplish complete analyte conversion to CO₂, while being narrow enough to preserve narrow analyte peak shapes within the continuous flow carrier stream for subsequent IRMS analysis.
The current step change when He carrier gas passes from GC capillary columns (inner diameter, i.d.: 0.22–0.32 mm) to commercial combustion tubes (i.d.: 0.5 mm) generates substantial peak broadening. Even smaller GC capillaries are needed, however, to support GCxGC applications and to improve sensitivity by reducing flows and, therefore, minimizing losses in an open split before IRMS. We aim to explore the promise of two designs - a wall-coated capillary (WCC) reactor and a solid-electrolyte reactor (SER) - to pioneer robust solutions for miniaturized reactors that can facilitate routine GCxGC-C-IRMS.