Loose septa are designed for manual insertion into autosampler vial caps that do not include pre‑installed septa. This subcategory includes pre‑slit and non‑slit septa manufactured in a variety of materials for use with open‑hole screw caps, snap caps, and other compatible cap formats in chromatography workflows.
Septa are available in multiple material constructions, including silicone/PTFE, PTFE/silicone, butyl rubber/PTFE, and PTFE‑only configurations, allowing selection based on analytical sensitivity, solvent compatibility, and injection requirements. Silicone‑ and PTFE‑based septa are among the most commonly used options in HPLC and GC applications, offering a balance of pierceability, chemical resistance, and resealing performance.
Pre‑slit septa are often selected for applications requiring reduced needle resistance and consistent penetration, while non‑slit septa may be preferred where maximum sealing integrity or extended resealing performance is required. Septum size and thickness must be carefully matched to the specific cap type, as screw caps and snap caps require different septa dimensions for proper fit and sealing.
Selection of the appropriate septum material and configuration plays a key role in minimizing background interference, preventing sample loss, and maintaining reproducible injection performance across chromatography systems.
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