The Effect of Bottle Fill Rate and Pour Technique on the Recovery of Volatile Organics

摘要

This field study was conducted to examine whether the method or the flow rate (fill rate) used to fill a sample vial affects recovery of volatile organics (VOCs). To our knowledge, there have not been any systematic studies that have examined this issue. For this field study, three fill rates (50 mL/min, 250 mL/min, and ～1 L/min) and three filling methods (top-pour, side-pour, and bottom-fill) were used to fill sample vials. We found that the bottom-fill method, with the tubing submerged in the sample as it fills, yielded the greatest recovery (i.e., highest concentrations) of VOCs. Little improvement was observed by pouring down the side of a vial vs. simply pouring straight down from the top. We also found that filling the vials at the fastest fill rate (～1 L/min) yielded higher recovery than the slowest fill rate (50 mL/min) using all three filling methods. These results are counter to prevailing guidance and conventional wisdom that slower filling is preferable to faster filling and that pouring down the side of a sample vial is the best practice for VOC sampling. However, because we were unable to randomize the order the samples were collected with respect to fill rate, we recommend a follow-on study be conducted that will allow us to confirm our findings and better determine which fill rates minimize losses of VOCs.