Development of a method for determination of volatile organic compounds (C-6-C-9) by thermal desorption-gas chromatography. Application to urban and rural atmospheres.

An analytical method for the determination of 15 Volatile Organic Compounds (VOC): benzene, n-heptane, toluene, n-octane, chlorobenzene, ethylbenzene, m-xylene, o-xylene, p-xylene, isopropylbenzene, n-propylbenzene, n-decane, 1,4-dichlorobenzene, 1,3-dichlorobenzene and 1,2-dichlorobenzene, by therm al desorption coupled with gas chromatography (GC) was proposed. The flame ionisation detector (FID) and mass spectrometry (MS) detector were used. Th e variables that have an influence on the desorption process (time, inert g as flow and temperature) were studied, obtaining detection limit ranges fro m 15 to 120 pg (GC-FID), 3.8 to 32 pg (GC-MS, SIM mode) and 15 to 300 pg (G C-MS, SCAN mode). In order to detect possible VOC urban sources, samples we re taken from 6 points in A Coruna (N.W. Spain) to analyse. Sampling time a nd flow rate were 30 minutes and 50 mL/min respectively. VOC profile and th eir total concentrations can be considered as typical of an urban area. Oth er samples were also obtained from a nearly rural zone to determine the inf luence of these VOC sources.