Effect of the Carrier Gas on the Sensitivity of a Thermal-conductivity Detector in Gas Chromatography

Abstract

IN a recent communication¹, the sensitivity, dt/dx, of a thermal-conductivity cell to small amounts of organic vapours was derived from : where t ₁ and t ₀ are the temperatures of the hot wire and body of the cell respectively, a is constant, and K ₁ is the thermal conductivity of the carrier gas. The sensitivity was then shown to be : where K ₂ is the thermal conductivity of the organic vapour and x is its concentration in the carrier gas. From equation 2, carrier gases of low thermal conductivity would be expected to produce the highest sensitivities. However, in practice a is usually varied, and sensitivities should be compared at equal values of t ₁. Carrier gases of high thermal conductivity would then give the highest sensitivities.