A high resolution GC-analysis method for determination of C2-C10 hydrocarbons in air samples

An analytical method for the determination of non-methane hydrocarbons (NMHC) in air was developed using simultaneously pressure and temperature programmed gas chromatography (GC) on a capillary column. The separation of C2-C10 hydrocarbons was performed in a single GC-run using a fused silica capillary column (FSCC) with a chemically bonded non-polar stationary phase (CP-Sil-5-CB). A combination of on-column cryofocusing and GC reinjection provided baseline separation of C2 hydrocarbons at subambient initial temperature (?40°C). The cryofocusing was performed on the column head immersed in liquid nitrogen. Quantitative retention of all C2-C10 hydrocarbons was achieved only when a temperature gradient is created along the cooled column section. The focused components are eluted from the column head without supplementary heating by removing the coolant. To eliminate matrix effects, the enrichment procedure was designed to remove CO₂ and H₂O. The detection limit was found to be 2.0 × 10^?12 g propane.