The Effect of the Linear Velocity on the Detector Response and Effective Carbon Number: The Role of the Experimental Conditions in the Quantitative Analysis

Abstract

Since its introduction in 1957 the Flame Ionization Detector (FID) is the most widely used Gas Chromatographic (GC) detector. Nowadays there is no Gas Chromatographic laboratory without apparatus containing a Flame Ionization Detector. However, the operation mechanism of the hydrogen flame and signal production is still not completely obvious. The FID response for hydrocarbons is proportional to the carbon content of the compound, while substances that contain heteroatoms yield smaller responses. In the Gas Chromatographic practice, a special relative response factor called Effective Carbon Number (ECN) is used for the expression of the response for molecules containing heteroatom. In the literature there are signal modifying constants published by different authors, which are typical of the carbon atoms and heteroatoms in the different chemical bonds. Although these constants express the nature of the modification (increase or decrease) the exact modifying value always depends on the chromatographic parameters and the molecular structure. If we want to apply the ECN method for our calculations these constants should be determined for our specific Gas Chromatographic system. In our earlier study we investigated the effect of the temperature of the injector, column and detector, the mode of the injection and the concentration level of the substance. The aim of this paper is to investigate the effect of the linear velocity on the response of the Flame Ionization Detector as a mass flow rate sensitive detector in the case of capillary column.