In volatile organics (VOC) sampling, what is the required handling when filling the sample vials?

• A. Fill each vial completely with the sample to create a headspace.
• B. Leave space in the vial to avoid overfilling.
• C. Fill each vial completely with the sample (creating a meniscus), but do not overflow/flush out the preservative; cap and invert several times to mix.
• D. Cap and invert the vial only after the sample has been stored for 24 hours.

Answer: (C)

When handling VOC samples, the goal is to keep the sample as stable as possible from the moment of collection. Filling the vial up to near capacity so a small meniscus forms minimizes the air space that can exchange with the sample. This reduces the chance of VOCs volatilizing into headspace or reacting with ambient air, helping to preserve the true composition of the sample until analysis. It’s important not to overflow, which could push preservative out or contaminate the exterior, and not to leave a large air gap that would enable more volatilization.

After filling, cap the vial promptly and invert several times to mix in the preservative. Thorough mixing ensures the preservative is evenly distributed throughout the sample, stabilizing it and preventing degradation or changes during storage and transport. Delaying sealing, or failing to mix in the preservative, can compromise sample integrity and data quality.