A low-bleed septum is not completely free of bleeding. The type of bleeding that occurs varies with the septum and results in different patterns on chromatograms. In the case of high-sensitivity analysis, it is necessary to select a septum whose bleeding will not occur at a point that interferes with the peak of the target compound. Conditioning for several hours between 120 ℃ and 200 ℃ after extraction with hexane may help to reduce bleeding.
In the case of using a syringe for AOC, it is recommended to exchange the septum after about 100 injections. If the outside diameter of a needle of a gastight syringe is thick, it is recommended to exchange after about 50 injections.