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-diff usion 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-I.

Measurement of Helium Metastable Atom Densities in a Plasma-Based Ambient Ionization Source

“…Dielectric-barrier discharges can be formed using a variety of configurations, with a range of dimensions, power, frequency, electrode spacing, and orientations. , The discharge used in this study is a variant of a discharge described by Rice et al, and later used in this lab for element selective GC detection. , The discharge was generated in a capillary (3 mm o.d., 1 mm i.d., 80 mm long), between an internal grounded needle electrode and an outer copper electrode (7.3 mm o.d., 3 mm i.d., and 3 mm long). The ring electrode was placed 1 cm from the tip of the capillary, and the distance between the two electrodes was 58 mm.…”

Determination of Extractable Organic Chlorine and Bromine by Probe Injection Dual-Microplasma Atomic Emission Spectrometry

“…Therefore, in the present work, a 350 kHz helium plasma was utilized due to the straightforward energy coupling and because of the excellent analytical properties, as demonstrated for gas chromatographic detection. [24][25][26][27][28][29][30][31][32][33][34][35][36][37] To enhance the sensitivity of the method, the extraction solvent was evaporated prior to analysis. The solid sample was subsequently introduced at the plasma inlet by a sample probe.…”

“…Microwaves have frequently been applied to sustain small helium plasmas, but the energy coupling is relatively complicated and requires the use of special cavities. Therefore, in the present work, a 350 kHz helium plasma was utilized due to the straightforward energy coupling and because of the excellent analytical properties, as demonstrated for gas chromatographic detection. − To enhance the sensitivity of the method, the extraction solvent was evaporated prior to analysis. The solid sample was subsequently introduced at the plasma inlet by a sample probe.…”