Select septa based on the injection port temperature you will use. Generally, septa with lower thermal limits are softer, and thus are easier to seal or to pierce with a needle. However, softer septa are more prone to damage caused by over tightening the septum nut, and this can reduce the life of the septum. Change all septa regularly, regardless of their thermal limits, to avoid coring and bleed.
Tips for Handling Septa
All septa, regardless of composition, puncturability, or resistance to thermal degradation will fail if they are mishandled. Overtightening a septum nut invariably will reduce septum lifetime by increasing coring/splitting. All septa contain volatile materials (e.g., phthalates) that are released when the septum is heated (septum bleed). Because most GCs are equipped with a septum purge, septum bleed generally will disappear within 30 minutes after installing a new septum and exposing it to normal injector temperatures.
