Integrity of VOA-Vial Seals

摘要

Preservation of soil samples for the analysis of volatile organic compounds(VOCs) requires both the inhibition of VOC degradation and the restriction of vapor movement in or out of the sample container. Clear, 40, -ml glass VOA vials manufactured by the four major U.S. glass manufacturers were tested for seal integrity. Visual inspection revealed a various of imperfections ranging from small indentations, bumps, and scratches on vial threads or lips, through obvious defects, such as large indentations or grooves in the vial lips and chipped or broken glass. The aluminum plate vacuum test proved to be unreliable in identifying potentially leaky vials. The septa-seal vacuum test was conducted twice on the 80 selected vials. Results show that mean VOC concentrations after 14 days storage generally were within +-20% of the known concentration with a majority of the concentrations within +-15% of their known values. Only 1 vial lost VOCs and that was due to a large chip in the vial's lip and neck. These findings indicate that the silicone septa are flexible enough to overcome most vial imperfections and form a complete seal against VOC loss.