A modular, roving gc/ms system for fast, repetitive analysis of voc/soc gradients and trends

摘要

It is difficult to botain representative VOC (volatile organic compound) and SOC (semi-volatile organic compound) measurements in ambient environments which exhibit complex concentration gradients and/or trends when one must rely on limited numbers of analyses from simple pooling or averaging techniques. A more efffective approach is to perform large numbers of spacially and/or temporally resolved analyses to permit detailed mapping or profiling of local gradients and trends. This paper describes a roving GC/MS system based on teh combination of a Hewlett-Packard model 5972 MSD (mass selective detector), a Femto Scan Enviroprobe repetitive vapor sampling inlet with short capillary GC column, an Alcatel Micro HV oil-less vacuum pump stack and a Pentium notebook PC. Teh roving system is further equipped with differential GPS (global positioning system) and radio transeceiver caabilities thereby enabling remote tracking of vehicle location and local VOC concentrations. Laboratory tests demonstrate lower detection limits of <10ppb for BRX (benzene, toluene and xylene), corresponding to minimum detectable quantities of <40 femtograms, and maximum analysis speeds of up to 5 GC peaks per second on a mixture of volatile ketones.