Compared to many sophisticated analytical instruments in the laboratory, vials may be small, but their proper selection and usage play a crucial role in experiment efficiency, processes, and data accuracy. Incorrect choices of vials can lead to various issues, including poor sealing causing analyte volatilization, chromatographic peaks due to solvent-septa interaction, damage to automatic samplers, poor injection repeatability, sample degradation, and sample adsorption. Therefore, when selecting the right vials for your application, you must carefully consider three key factors: septa, caps, and the vial itself.

Septa Selection:

  1. PTFE:

    • Recommended for single injections.
    • Excellent solvent resistance and chemical compatibility.
    • Does not reseal after piercing.
    • Not suitable for long-term sample storage.
  2. PTFE/Silicone:

    • Recommended for multiple injections and sample storage.
    • Exhibits excellent resealing properties.
    • Prior to piercing, has chemical resistance of PTFE, post-piercing exhibits chemical compatibility of silicone.
    • Operating temperature range: -40 ℃ to 200 ℃.
  3. PTFE/Silicone Pre-slit:

    • Provides excellent ventilation to prevent vacuum formation in the vial, ensuring outstanding sampling reproducibility.
    • Eliminates needle clogging at the bottom after sampling.
    • Good resealing capability.
    • Recommended for multiple injections.
    • Operating temperature range: -40 ℃ to 200 ℃.
  4. Non-sealed PE (Polyethylene):

    • Possesses similar advantages as PTFE.

Cap Selection:

  1. Screw Cap:

    • Excellent sealing without the need for any tools.
  2. Crimp Cap:

    • Aluminum crimp cap provides excellent sealing, reducing the risk of sample volatilization.
    • More heat-resistant in high-temperature experimental environments.
    • Requires a crimping tool for application.
  3. Snap Cap:

    • Sealing effectiveness is inferior to screw caps and crimp caps.
    • Press-on snap caps are suitable for storing powdered samples and are not ideal for transporting liquids.
    • Tight-fitting caps may be challenging to place and could potentially break.
  4. One-piece Cap/Septum:

    • Ensures that the septum and cap stay together during transport and when the cap is applied to the vial.
    • Prevents the septum from falling off during use.
    • Mitigates excessive evaporation, maintaining proper vial sealing.

Vial Material Selection:

  1. Type I, 33-Expansion Borosilicate Glass:

    • Exhibits high chemical inertness and is commonly used in analytical laboratories for high-quality experimental results.
  2. Type I, 51-Expansion Glass:

    • More alkaline than 33-expansion glass and suitable for various laboratory purposes.
  3. Deactivated Glass (DV):

    • Ideal for analytes strongly polar and prone to binding to the polar glass surface.
    • Surface treated with organosilane for hydrophobicity.
    • Can be stored indefinitely under dry conditions.
  4. Polypropylene (PP):

    • Non-reactive plastic suitable for situations where glass is not preferred.
    • Maintains good sealing even when exposed to flames during sealing.
    • Maximum use temperature: 135 ℃.

By considering these factors, you can make informed choices in selecting chromatography vial accessories, ensuring the success of your experiments with enhanced safety and accuracy.

By 向阳 翟


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