Selecting the correct sample vials is a crucial step in ensuring the accuracy, safety, and efficiency of experimental data. This is a systematic decision-making process that primarily revolves around four key dimensions: "Sample Characteristics," "Analytical Method," "Operational Workflow," and "Cost Control."
Below is a clear selection guide. You can make the optimal decision by answering a series of questions:

Step 1: Define Analytical Requirements (The Most Important Starting Point)

1. What is the Analytical Method?

   • Gas Chromatography (GC, GC-MS): Must use GC-specific vials (e.g., crimp vials). For headspace analysis, headspace vials are mandatory.

   • Liquid Chromatography (HPLC, UHPLC, LC-MS): Must use HPLC-specific vials (typically crimp or screw thread vials with a flat or conical insert bottom) to ensure compatibility with autosampler needle depth.

   • General Storage, Sample Prep, or Spectroscopic Analysis: Universal screw thread vials can be chosen for good sealing and ease of opening/closing.

   • Light-Sensitive Samples: Must choose amber/brown vials.

2. What are the Sample Characteristics?

   • Acidity/Alkalinity/Corrosiveness: Prioritize vials made of the most chemically inert Type I borosilicate glass. For strong bases or hydrofluoric acid, consider special polymer vials (e.g., PMP).

   • Adsorption Tendency: For trace proteins, peptides, or certain drug molecules, use vials with deactivated (e.g., silanized) surfaces to minimize wall adsorption.

   • Volatility: Must choose a vial cap system with the best sealing (e.g., crimp caps with PTFE/silicone septa) and use septa with small pre-slit openings.

   • Physical State: Standard vials for liquids; solid or semi-solid samples may require wide-mouth vials.

Step 2: Select Vial Body Material & Specifications

1. Select Vial Body Material:

   • Clear Borosilicate Glass (Type I): Most versatile and recommended. High chemical inertness, heat resistant, transparent. Suitable for most organic solvents and aqueous solutions.

   • Amber Borosilicate Glass: Used for all light-sensitive substances (e.g., vitamins, silver nitrate, certain dyes).

   • Plastic Vials (PP, PE, PMP):

     • Advantages: Shatterproof, lightweight, low cost. Suitable for aqueous solutions, non-organic solvents, high-speed centrifugation, storage, and transport.

     • Disadvantages: Poor tolerance to organic solvents (especially PP/PE), potential for plasticizer leaching, inferior gas barrier properties. PMP (Polymethylpentene) offers greater inertness and clarity close to glass, making it a better choice.

1. Select Closure Type & Sealing System:

• Select Volume:

  • Choose based on sample amount and instrument requirements. 2mL is common for chromatography. Ensure sufficient volume to immerse the injection needle while avoiding overfilling.

  • Common volumes: 0.3mL, 1mL, 2mL, 4mL, 10mL, 20mL, etc.

Step 3: Match Operations & Costs

1. Automation Compatibility:

   • Confirm that the vial's height, diameter, and bottom shape perfectly match your autosampler tray specifications. Common formats: 12 x 32 mm, 12 x 75 mm.

2. Pre-Cleaning & Pre-Treatment:

   • Routine Analysis: Purchasing certified clean, ready-to-use products is sufficient.

   • Trace/Ultra-trace Analysis: Requires selecting vials that have undergone stringent cleaning (e.g., tested by Karl Fischer method) or even deactivation treatment.

3. Cost & Efficiency Considerations:

• • High-volume Routine Analysis: Consider economical packaging (e.g., 100/pack, 1000/case).

  • Reducing Contamination & Human Error: Consider using vials with pre-printed ID codes or vials with pre-inserted inserts.

  • Balance Cost: Choose the most cost-effective solution that meets analytical requirements. For example, use screw thread vials for long-term storage and cheaper crimp vials for one-time injection analysis.

Golden Rules

• Prioritize following the consumable specifications recommended by the instrument manufacturer.

• For critical or new model analyses, always conduct small-batch tests to verify compatibility.

• Optimize cost under the premise of guaranteeing data accuracy. Avoid causing expensive instrument failures or invalid data by saving on consumable costs.