Chromatographers measure an injection s success by the degree to which it preserves the relative sample composition without interfering with resolution and by how well the injection process repeats from run to run. Unfortunately for many gas chromatographers, their samples chemistry and the repetitive nature of routine analyses gradually degrade inlet functionality. Appropriate setup and routine maintenance are necessary to achieve top performance during extended periods. Problem Sources Inlet problems arise from several sources. Chromatographers most often encounter problems caused by the mechanical degradation of the various key inlet consumables such as septa, liners, and ferrules.
Problems also can arise from maladjusted injection timing, temperature, and flow rates.
Difficulties caused by sample, inlet, or column mismatches also are a significant source of analysts injection-linked headaches. In this installment of GC Connections, I ll concentrate on selecting and maintaining consumable septa and inlet liners. Practicing chromatographers should think of consumables as just that - replaceable components to be used up in the course of normal analyses. The practice of trying to save money by waiting to replace consumable items until they fail is self-defeating. By the time a consumable item fails, the potential in lost time and analysis revenues may far exceed the cost of scheduled replacement.