Optimizing Sample Vials for Accurate PFAS Analysis: Key Considerations for Laboratories

Per- and polyfluoroalkyl substances (PFAS) are a class of man-made chemicals that have become a growing concern due to their persistence in the environment and potential adverse effects on human health. Often referred to as "forever chemicals," PFAS are resistant to degradation, which means they accumulate over time in water, soil, and living organisms. Exposure to PFAS has been linked to a variety of health issues, including cancer, liver damage, immune system suppression, and reproductive problems.

Given the widespread use of PFAS in consumer products like non-stick cookware, food packaging, and waterproof fabrics, as well as in industrial applications, their presence in the environment is almost ubiquitous. This has led to a global effort to detect and analyze PFAS in various matrices, from water samples to biological tissues. PFAS analysis typically involves liquid chromatography-tandem mass spectrometry (LC-MS/MS), a powerful technique capable of detecting trace levels of these substances in complex samples.

In PFAS testing, proper sample handling is essential to ensure accurate and reliable results. One often overlooked aspect is the selection of appropriate vials for sample storage, preparation, and delivery. Vials play a critical role in maintaining the integrity of PFAS samples throughout the testing process, especially when using LC-MS/MS, where contamination risks must be minimized.

Vials designed for PFAS analysis need to be made from materials that do not introduce contaminants or interact with the analytes of interest. Commonly used vials in PFAS analysis are often made from polypropylene (PP) or polymethylpentene (TPX). Each material has unique properties that make it suitable for different stages of sample handling, from collection to injection into the LC-MS/MS system.

When selecting vials for PFAS testing, it is important to consider the advantages and disadvantages of common materials that are used to create vials.

• Glass vials (not recommended) are widely used in many types of analysis due to their transparency and chemical resistance. However, for PFAS testing, glass vials can pose a risk of contamination, as PFAS can adsorb to the glass surface, leading to inaccurate results. Additionally, some manufacturing processes of glass may leave behind trace amounts of PFAS.
• Polypropylene (PP) vials (author's personal recommendation) are a popular choice for PFAS testing because they are less likely to leach contaminants and have a lower adsorption potential for PFAS compounds. PP vials are also cost-effective and chemically inert, making them ideal for long-term storage of PFAS samples.
• Polymethylpentene (TPX/PMP) vials offer a balance between chemical resistance and low adsorption properties. TPX is particularly suitable for PFAS analysis due to its hydrophobic nature, which helps minimize interaction with PFAS analytes. However, TPX vials can be more expensive than PP options, so cost considerations may factor into their use.

While choosing the right vial material is crucial, the septum material used in vial caps is just as important. General lab vials often use polytetrafluoroethylene (PTFE) as the septum material due to its chemical resistance. However, since PTFE itself contains fluorine, it poses a significant risk of introducing PFAS contamination into samples. Using PTFE septa in PFAS analysis can compromise results by adding background contamination, leading to false positives or elevated PFAS readings.

To avoid this issue, labs should opt for polyimide septa, which are free from fluorine and do not contribute to PFAS contamination. Polyimide septa provide excellent chemical resistance and sealing properties without the risk of interfering with PFAS detection, ensuring the integrity of the analysis.

In some cases, laboratories may need to work with small volumes of PFAS samples. When the sample volume is low, the liquid may not reach the syringe needle during extraction or injection into the LC-MS/MS system, leading to inefficient sampling. This is where vial inserts become essential.

Inserts are small, conical glass or plastic tubes placed inside the vials to increase the height of the sample, making it easier for the syringe to access the liquid. Using inserts allows labs to work with smaller sample volumes without sacrificing accuracy. This not only saves valuable sample material but also ensures consistent and reliable results, especially in PFAS analysis where trace detection is crucial.

Choosing the right vials and septa for PFAS analysis is a critical step in ensuring accurate and contamination-free results. From avoiding glass vials due to potential adsorption issues to selecting polyimide septa over PTFE, each decision can directly impact the success of the analysis. The use of inserts further enhances sample handling, allowing for efficient processing of low-volume samples.

For laboratories looking to optimize their PFAS testing workflows, WelchLab offers a range of dedicated vial kits designed specifically for this type of analysis. Consisting of high-quality PP vials and polyimide-sealed caps, WelchLab’s kits ensure that your PFAS testing is free from contamination risks, delivering reliable and reproducible results every time.