The BTEX Family of Pollutants in Automobiles and Ambient Air Measured by Jet-REMPI

The BTEX group of hazardous air pollutants comprises benzene, toluene, ethyl benzene, and the three xylene isomers, often found together in air mixtures. Each is thought to be carcinogenic. We have used the Jet-REMPI method (resonantly enhanced multiphoton ionization) followed by time of flight mass spectrometry to measure these compounds. Samples were taken from open containers, gasoline tank headspace, automobile exhaust, and ambient air. In ambient air, we collect samples on a filter cartridge for 3.5 hours, to obtain enough sample to use GC/MS as a survey tool. Only toluene shows in the GC/MS scan as a small signal. To use Jet-REMPI, we must dilute the sample a factor of 20,000 to avoid overloading the instrument, and simulate a corresponding sampling time of about 1 sec. All of the BTEX compounds are seen readily in the Jet-REMPI instrument, and the three isomers of xylene show different REMPI patterns even though all are at the same mass. All compounds are present at a few part per billion concentration. This work was supported by the Environmental Protection Agency and the NSF Research Experience for Undergraduates Program.