SAMPLING AND ANALYSIS OF TERPENES IN AIR - AN INTERLABORATORY COMPARISON

An interlaboratory comparison on the sampling and analysis of terpenes in air was held within the framework of the BEMA (Biogenic Emissions in the Mediterranean Area) project in May 1995. Samples were drawn and analysed by 10 European laboratories from a dynamic artificial air ge nerator in which five terpenes were present at low ng l(-1) levels and ozone varied between 8 and 125 ppbv. Significant improvements over pr evious inter-comparison exercises in the quality of results were obser ved. At the ozone mixing ratio of 8 ppbv a good agreement among labora tories was obtained for all test compounds with mean values close to t he target concentration. At higher mixing ratios, ozone reduced terpen e recoveries and decreased the precision of the measurements due to oz onolysis during sampling. For P-pinene this effect was negligible but for the more reactive compounds significant losses were observed in so me laboratories (cis-beta-ocimene = trans-beta-ocimene > linalool > d- limonene). The detrimental effect of ozone was significantly lower for the laboratories which removed ozone prior to sampling by scrubbers. Parallel sampling was carried out with a standardised sampler and each individual laboratory's own device. A good agreement between the two sets of results was obtained, clearly showing that the majority of lab oratories used efficient sampling systems. Two different standard solu tions were analysed by each laboratory. Only in a few cases did interf erence in the GC separation cause problems for the quantification of t he terpenes (nonanal/linalool). However, making up of standards for th e calibration of the analytical equipment (GC-MS or GC-FID) was pointe d out as a source of error in some laboratories. (C) 1997 Elsevier Sci ence Ltd.