Nitrogen-selective detection for gas chromatography with a helium radiofrequency plasma detector. Invited lecture

Abstract

A helium r.f. plasma was characterized for the selective detection of nitrogen in gas chromatographic eluents by atomic emission spectrometry. Nitrogen emission was detected at 868 nm. The principle sources of background emission at that wavelength were identified. The largest single source was back-diffusion from the discharge exit. There were also significant contributions from impurities in the high-grade make-up and reagent gases. An avalanche photodiode was evaluated as a photodetector and found to be superior to a photomultiplier tube for this application. End-on and side-on optical collection geometries were modelled by a computer. The detection limit for nitrogen in the discharge was 57 pg s^–1.