Response of the Flame lonization Detector to Some Perfluorocarbons

The response of an FID to CF4, C 2 F 6, c-CgF12 and c-C7F1 4 was determined over a wide range of operating conditions. The high carbon number fluorocarbons showed response values similar to those of the corresponding hydrocarbons and their relative response values were almost independent of operating conditions and near to unity, provided higher H 2 flowrates than usual for hydrocarbons were employed. For the light fluorocarbons, in addition to their much lower response, it was difficult to find suitable operating conditions for the FID due to the high dependence upon flowrates, etc. From the data it was also concluded that different mechanisms determining the height of the response were operating. For low carbon numbers and/or low H 2 flowrates the main governing factor seemed to be the flame temperature, whereas at high carbon numbers and/or high H 2 flowrates, the temperature became of little importance