When working with small sample volumes, the choice of HPLC autosampler vial becomes a critical factor. Low-volume vials require special attention to ensure optimal performance and data quality. Here are 5 key considerations for selecting the best low-volume autosampler vials for your HPLC analysis:
The vial capacity should be just large enough to hold the sample volume with minimal dead space. Typical small volume vial sizes range from 150µL to 2ml. Matching the vial size to the sample volume is essential to minimise dead volume and the associated risks. Dead volume increases the exposed surface area of the sample, which increases the potential for evaporation – especially for volatile analytes. This can alter the original sample concentration and lead to inaccurate HPLC results. By selecting the smallest vial that can hold the entire sample, you eliminate excess headspace and optimise the vial-to-sample ratio.
Small volume vials are typically made of glass or various polymeric materials such as polypropylene. Glass vials offer excellent chemical compatibility and very low sample adsorption, making them a popular choice. Polymer vials are often more economical, but may have increased analyte binding depending on the sample chemistry. When selecting the vial material, consider the specific chemical nature and properties of your HPLC samples to ensure compatibility and minimise potential interactions or sample loss.
Proper sealing of small volume vials is critical to prevent evaporation and contamination of the sample. Screw caps with PTFE/silicone septa are a common and reliable sealing mechanism for autosampler vials, and crimp caps are another option that provide a secure seal. Regardless of the closure type, it is important to ensure a tight, reliable seal that maintains sample integrity throughout storage and analysis.
For micro-scale samples with volumes below 300 μL, the use of micro vial inserts can be very beneficial. These specialised inserts fit into standard 2 mL autosampler vials, effectively reducing the overall headspace and dead volume. Inserts are typically made of clear glass materials and have a smaller sample contact area compared to the full vial. The use of vial inserts helps to reduce evaporation and maintain sample concentration for your HPLC runs.
Small volume vials require extra care and consideration when handling to avoid sample loss or contamination. Automated liquid handlers and autosamplers are ideal for precise and repetitive low-volume injections. When selecting your low-volume vials, make sure they are compatible with the equipment and instrumentation you will be using for HPLC analysis. Proper vial handling and automated processes help maintain sample integrity and produce reliable, high-quality data.
Careful consideration of these 5 key factors will help you select the optimal low volume HPLC autosampler vials for your application. Choosing the right vials will minimise sample loss, maintain sample integrity and provide reliable, high quality data from your HPLC analysis.