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Evaluation of New Moisture Management Techniques for the Analysis of Volatile Organic Compounds in Environmental Samples
Julie Kancler, Tom Hartlein, Mark Krigbaum
Tekmar-Dohrmann Velocity XPT™ has three new techniques to control water. Each of these techniques are compared in this study. The concentrators were interfaced to a HP 5890 gas chromatograph (GC) with a thermal conductivity detector (TCD). The analytical standard used was a California WIP standard. This standard was chosen for its variation in both boiling point and polarity of compounds. The detector was chosen because of its high response to water and methanol making it the "worst case" scenario. Table 1 lists the parameters used for each of the instruments. All conditions remain constant unless otherwise noted.
Comparing Dry Purge Flow Rates
Three flow rates were compared; 0 ml/min, 200 ml/min and 400 ml/min in this study. Figure 1 shows the comparison of varying flow rates using the Velocity XPT electronic flow control feature. The blue chromatogram, at the top, represents no dry purge flow for 1 minute. The time frame of one minute was chosen to keep conditions constant throughout the study in which only the flow rates were varied. Under these conditions there is only one peak for water and methanol, indicating no water removal. The red chromatogram, in the middle, represents 200 ml/min flow rate, it shows separation between water and methanol, indicating water removal has taken place. Water is the first smaller peak, methanol is the larger second peak. Finally, the green chromatogram, at the bottom, represents 400 ml/min flow rate and shows the most efficient removal. However, at this high flow rate gaseous compounds may begin to break through the sorbent packing of the trap. Table 2 shows the areas of each of the analytes.
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