Capillar Gas Chromatography With Laser Optothermal Detection

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.