CHROMATOGRAPHY WITH DENSE GASES .1. ON THE SENSITIVITY OF A FLAME IONIZATION DETECTOR IN A SUPERCRITICAL FLUID CHROMATOGRAPHY

A capillary restrictor for supercritical fluid chromatography (SFC) with CO2 was made by using a micro torch and fine emery cloths or grinding blocks. This restrictor could be drawn out either directly from the end of the analytical capillary column, or from a short piece of any capillary, which was then connected to the analytical column by standard techniques. It was found that the base current of a flame ionisation detector (FID) depends strongly on the position of the capillary end with respect to the FID flame tip and on the CO2 grade, of course. Best results have been achieved at around 5 to 7 mm distance between the restrictor and the flame tip ends, and using SFC grade CO2.