Capillar Gas Chromatography With Laser Optothermal Detection

Abstract

The design of a through-flow laser opto-thermal (OT) detector intended for operation as a selective chromatographic detector in combination with capillary columns is described. The main advantage of such a detector is its relative simplicity and high spatial resolution. A new differential scheme of OT detector which can reduce the background signals of scattered radiation by about 10² times is suggested. The threshold sensitivity of OT detector is experimentally estimated to be equal to about 7 ng (ethanol). The higher selectivity of the developed system “gas capillary chromatograph + laser OT spectrometer” has been demonstrated by analyzing a mixture of five atomatic hydrocarbons with the use of a tunable CO₂ laser. Recommendations for further modification of the equipment are given.