Reduction of biogenic VOC sampling losses from ozone via trans-2-butene addition.

The continuous addition of trans-2-butene to air containing ozone-reactive volatile and semivolatile organic compounds prior to sampling on Tenax-TA adsorbent was found to be an effective means of removing ozone and reducing analyte losses of ozone reactive biogenic volatile organic compounds (BVOCs). To allow sufficient time for ozone scavenging to occur, the reacting mixture is passed through a heated (40 degrees C) coil of Sulfinert (Restek Corp., Bellefonte, PA) treated stainless steel tubing. The method was evaluated using a test mixture consisting of terpenes, terpenoid alcohols, and sesquiterpenes at part per trillion (pptv) levels in air in the presence of 100 parts per billion (ppbv) of ozone. The continuous addition of trans-2-butene to produce 600 ppm (ppmv) was found to be completely effective in controlling VOC losses on Tenax-TA as long as (1) sufficient time is allowed for the ozone scavenging to occur before the VOCs are adsorbed and (2) analyte enrichment on the adsorbentdoes not approach the hydroxyl radical scavenging capacity of the trans-2-butene. A manganese dioxide (MnO2) coated copper screen ozone scrubber was also tested and found to be of very limited utility.