METHOD DEVELOPMENT AND FIELD-MEASUREMENTS FOR POLAR VOLATILE ORGANIC-COMPOUNDS IN AMBIENT AIR

This paper reports on a program which had two main objectives: (1) to develop an analytical method for polar volatile organic compounds (PVO Cs) in ambient air using sample collection in canisters and (2) to per form PVOC analysis on ambient air samples collected at two sites forme rly used in the U.S. EPA's Toxic Air Monitoring Study (TAMS). The anal ytical method consists of gas chromatographic separation of PVOCs with quantification by a quadrupole ion trap mass spectrometer. In order t o achieve proper chromatographic resolution of the PVOCs, it was neces sary to use a two-stage adsorbent trap to separate water from the samp le prior to GC analysis. Detection limits for a group of 14 target PVO Cs range from 0.2 to 1 ppbv in atmospheric samples, using electron imp act (EI) ionization in the ion trap detector. The method has been used on canister samples collected over 24-h intervals on a regular basis over 1 year at former TAMS sites in Boston and Houston, and on occasio nal samples collected in other studies. The PVOCs most often found in ambient samples include methanol, ethanol, acetone, 2-propanol, methyl ethyl ketone, and 1-butanol. Measured levels of these species often s ubstantially exceed the levels of benzene and toluene present in the s ame samples. The performance of the method in field sampling for PVOCs is comparable to that of the TO- 14 method for nonpolar VOCs, though variability in canister sampling appears greater for the PVOCs, presum ably due to the adsorptive behavior of these compounds. Possible impro vements in PVOC sampling and analysis are also suggested.