GC Septa Guide
High temperatures and low bleed are features of both septa. Septa 77 has become a mainstay in many labs but Septa BTO is Bleed and Temperature Optimized to achieve even greater functional performance. Formulated to extend low-bleed and outstanding mechanical properties to the highest temperature applications, it retains remarkable softness and pierceability while virtually eliminating injection port adhesion.
(Septa in image were baked in a GC oven at 290° C for one week. Septa BTO® remains soft and pliable. Septa 77® is pliable but slightly stiff. The Low-Bleed Green Septum is brittle; it shattered on cooling.)
The actual septum temperature in most ports set at 400° C is usually in the range of 280° C or less (though one inch into the port it will be 400° C.) Compared with popular competing low bleed septa, Septa BTO remains soft and exhibits less bleed even under severe operating conditions.
Traditional methods of manufacturing low-bleed septa often result in a hardened silicone. Some aspects can be conditioned by heating in the injection port, but once punctured, the exposed internal components tend to show bleed. Septa BTO is carefully processed to achieve exceptionally low bleed levels without sacrificing softness.
This issue causes plugged needles or columns. The enhanced resealability and durability of soft septa at high temperatures reduces the incidence of coring, allowing for use of wider needles or needles that are slightly bent, without a needle guide. Even so, the recommendation is to use a needle guide since it extends life to any septum by confining punctures to a small area. Septa BTO is ideal for autosamplers because of its superior injection characteristics.
