Effect of Water Vapour on the Sensitivity of a Flame Ionization Detector for Gas Chromatography

Abstract

IN a previous communication¹, we showed that the sensitivity of a macro-argon detector for gas chromatography is quite markedly affected by the presence of water vapour in the carrier gas stream of argon entering the detector. It was shown that a change in the water-vapour concentration in the argon carrier gas-stream from 8 to 10 p.p.m. v/v reduced the sensitivity of the detector to a constant level of 5.8 p.p.m. v/v of di-ethyl ether vapour by some 20 per cent. It is commonly stated that the sensitivity of a flame ionization detector is little affected by the presence of water vapour^2,3, but no quantitative data are given. Entiknap⁴ reports that the sensitivity of a flame-ionization detector to alcohols was between three and six times as high for aqueous solutions of alcohol as for pure alcohol, when alcohol samples were placed on the chromatographic column. In order to be able to use the flame ionization detector as a standard with which to compare the performance of other detectors, it was necessary to have quantitative data on the effect of water vapour on the sensitivity of this detector.