Introduction

Per- and Polyfluoroalkyl Substances (PFAS) are analyzed at extremely low concentration levels, making proper sample handling a critical component of analytical accuracy. The selection of sampling containers, storage vessels, autosampler vials, and closures can directly affect recovery, stability, and reproducibility.  Because PFAS compounds may interact differently with various materials, it is important to use container types that are appropriate for each stage of the analytical process.

Importance of Container Selection

PFAS analyses often require careful control of sample contact surfaces to minimize:

• Adsorption losses
• Contamination risks
• Sample instability
• Quantitation variability
• Recovery differences

Improper container selection may contribute to lower recoveries or inconsistent analytical results.

Sample Collection and Storage Containers

For routine PFAS sampling and storage, plastic containers are generally preferred.

Recommended Materials

Commonly recommended materials include:

• High-Density Polyethylene (HDPE)
• Polypropylene (PP)

These materials are widely used for environmental and laboratory PFAS sampling because they help support consistent analyte recovery during storage and handling.  Whenever possible, matching HDPE or polypropylene caps should also be used.

Considerations for Glass Containers

Glass is commonly used throughout analytical laboratories; however, special consideration should be given when storing PFAS samples.  PFAS compounds may adsorb to glass surfaces, particularly during extended storage periods. This adsorption can potentially influence measured concentrations and recovery values.  For this reason, glass is generally not the preferred material for long-term PFAS sample storage.

Calibration Standards

While plastic containers are often selected for sample collection and storage, calibration standards are frequently prepared and maintained in:

Amber Glass Vials

Benefits include:

• Protection from light exposure
• Compatibility with many standard preparation procedures
• Broad laboratory acceptance

Container suitability should always be verified according to internal procedures and validated methods.

Autosampler Vials for PFAS Analysis

For routine LC-MS analysis, polypropylene autosampler vials are commonly used.

Benefits of Polypropylene Vials

• Reduced adsorption concerns
• Excellent chemical resistance
• Compatibility with aqueous-organic solvent systems
• Suitability for trace-level PFAS analyses

Polypropylene autosampler vials have become a common choice in many PFAS laboratories.

Solvent Considerations

A solvent mixture frequently used for PFAS sample preparation is:  50% Methanol / 50% Water.  This composition can help:

• Dissolve PFAS compounds effectively
• Maintain analytes in solution
• Improve sample consistency
• Support reproducible analysis

Method-specific solvent requirements should always take precedence.

Cap Selection and Quantitative Accuracy

Cap performance can play an important role in maintaining sample integrity.  Repeated septum punctures and poor sealing performance may contribute to:

• Solvent evaporation
• Changes in analyte concentration
• Sample variability
• Quantitative errors

For low-level PFAS analyses, maintaining a reliable seal is particularly important.

Recommended Closure Practices

To minimize variability:

• Use properly sealed caps.
• Replace punctured closures when appropriate.
• Avoid long-term storage in repeatedly penetrated vials.
• Verify cap compatibility with the selected vial material.

Replacing caps during extended analytical workflows can help maintain consistent sample conditions.

Sample Mixing Prior to Analysis

Before injection, thorough mixing is recommended.

Vortex Mixing

Vortexing helps:

• Create a homogeneous solution
• Improve analyte distribution
• Enhance reproducibility
• Reduce variability associated with settling

This step may be especially important for certain longer-chain PFAS compounds.

Recommended Best Practices

For optimal PFAS analytical performance:

• Use HDPE or polypropylene containers for sample collection.
• Consider polypropylene autosampler vials for LC-MS analysis.
• Use appropriate closures to minimize evaporation.
• Minimize unnecessary sample transfers.
• Mix samples thoroughly before injection.
• Follow validated laboratory procedures for all stages of sample handling.

Conclusion

Successful PFAS analysis requires careful consideration of sample contact materials throughout the analytical workflow. HDPE and polypropylene containers are commonly recommended for sample collection and storage, while polypropylene autosampler vials are often preferred for LC-MS analysis. Proper cap selection, solvent management, and sample mixing practices can further improve recovery, reproducibility, and overall data quality.