HPLC Caps & Septa — 9 mm Screw Caps and Septa

Primary uses

• Seals a chromatography vial against evaporation and contamination
• Provides a resealable membrane the autosampler needle can pierce repeatedly
• Keeps the closure format consistent with the vial thread and the instrument tray

Applications

• Sealing HPLC, UHPLC and GC autosampler vials
• Headspace and volatile-sample workflows requiring a defined seal
• Multiple-injection sequences from one vial
• Sample storage between preparation and analysis

Advantages

• Bonded and pre-assembled formats remove the assembly step and the risk of a septum being fitted the wrong way round
• Pre-slit septa reduce coring and needle wear on sequences that inject repeatedly from the same vial
• Septum materials are offered in several combinations, so a laboratory can match the closure to the solvent rather than to habit

Limitations to consider

• Repeated piercing eventually compromises any septum, and coring particles can be carried into the sample
• Septum material determines background and extractable behaviour, which matters most at trace level and in volatile work
• Cap thread and vial thread must match exactly; a nearly correct thread leaks over a long sequence
• Every numeric property — assay, purity, residual content, pore size, retention behaviour, ash content, extractables, thickness, capacity and dimensional tolerance — is a property of one manufactured item from one production line. Values are read from the manufacturer's own technical documentation for the exact item offered and confirmed at quotation, never quoted from a category page.
• A manufacturer declaration and a verified result are not the same thing. Declarations state what the manufacturer controls to; suitability inside your own method, matrix and instrument is established by your own verification. Where a result must stand up inside an accredited scope, plan that verification before the item enters routine use.

How to choose the right grade

• Match the thread and diameter to the vial before comparing anything else
• Choose the septum facing material against the solvent in use and the number of injections planned from one vial
• Where background peaks are already an issue, evaluate the closure as a possible source before changing anything upstream
• Once a consumable is inside a validated method, changing it has a cost: the change has to be justified, trialled and documented. Continuity of the identical item usually matters more than unit price, so state the incumbent item and the property that must be matched when a second source is being qualified.
• Buyers frequently search using the catalogue name of a manufacturer they already use. Those are third-party trademarks belonging to their owners and are never used as an Allzone product identity. Where an equivalent is being considered, equivalence is assessed against the two sets of documentation and confirmed by the laboratory's own verification.
• Exact specification is confirmed against supplier documentation at quotation.

Typical grades

• Variant selection is made on the instrument, apparatus and test method rather than on a grade ladder
• Where a manufacturer operates distinct quality or cleanliness lines for the same item, the line is identified per offer
• Any declared property is read from the manufacturer documentation for the exact item offered, never assumed from a family name
• Regulatory listing, certification, food-contact status and any scheme approval belong to a specific item, facility and jurisdiction, and they change scope over time. State what your programme or customer requires at the enquiry stage so it is checked against current documentation for the offered item rather than assumed from a product name.
• These items are offered for industrial, food, feed, water, environmental and materials-testing work. Nothing here is offered, positioned or documented for medical, clinical, diagnostic or human-specimen use, and no such suitability is implied.