On‐column atomic emission detection in capillary gas chromatography using a radio frequency plasma

Abstract

AbstractDetection limits of heteroatoms and carbon were improved by eliminating the make‐up gas and sustaining a 350 kHz radio frequency plasma inside the end of a fused silica gas chromatography (GC) column (0.32 mm i.d.) for capillary GC with atomic emission detection. Due to the small internal diameter of the plasma cell, a stable plasma was maintained in only 1.5–3 mL min−1 of helium used as the GC carrier gas. The optical system consisted of a single low resolution monochromator for the near‐infrared region in order to develop a simple and low‐cost system. For on‐coloumn detection of C, H, S, Cl, Br, and I, the plasma was doped with traces of oxygen. The oxygen dopant served to suppress peak tailing and to maintain high selectivity and repeatability. Detection limits for C, H, S, Cl, Br, and I ranged from 0.9 to 11.8 pg s−1, and selectivities between 4 × 102 and 4 × 103 were obtained. On‐column F‐selective detection required a plasma doped with a mixture of hydrogen and oxygen. The detection limit for F was 13.0 pg s−1; however, the selectivity was poor (10) due to the low resolution of the spectrometer.