A New Sampler and Analysis Method for BTEX in Ambient Air


School of Public Health, Shahid Beheshti University of Medical Sciences, TEHRAN –IRAN.


Background: Benzene, toluene, ethylbenzene and xylene (BTEX) compounds are components of motor vehicle fuel. BTEX are released from exhausts of vehicles and also evaporation from the fuel tank, carburetor and crank case of engines. BTEX are dangerous chemicals that participate in photochemical reactions and produce secondary air pollutants such as ozone, peroxyacethyl nitrate, free radicals and nitrogen oxides. BTEX in ambient air of metropolitan areas has been the subject of concern in many studies through elaborate "Environmental Protection Agency" (EPA) method. Level of BTEX in the ambient air of major Iranian cities, has not been measured in concentration range of part per billion (ppbv) due to the inadequate sensitivity of available gas chromatography systems. The aim of this study was to improve the sensitivity of gas chromatography by using a special sampler and thermal desorber (Micro-Packed Injector). Materials and Methods: Our sampler consisted of a 5-centimeter stainless steel tube one millimeter in diameter packed with carbopacked B heat-conditioned samplers utilized for sampling atmospheric BTEX. It was subsequently injected to a custommade thermal desorber (225°C) which was assembled onto the injection port of a gas chromatography device for analysis. Results: BTEX standard atmospheres were analyzed with a gas chromatograph flame ionization detector (GC-FID) with linear range detection of 27.5-275ppb, 23.1-223.6ppb, 20-320-ppb, and 20-320ppb respectively. Conclusion: The Micro-Packed Injector (MPI) installed on ordinary GC-FID improved linear range detection of BTEX from previous ppm detection to ppb range. (Tanaffos 2008; 7(3): 47-52)