Characterization of a commercial gas chromatography-flame ionization detection system for the in situ determination of C-5-C-10 hydrocarbons in ambient air

A commercial automated gas chromatograph with preconcentration on solid ads orbents (AirmoVoc HC1010) was coupled with a mass spectrometer in parallel with the flame ionization detection (FID) system and characterized for its suitability for quasi continuous measurements of atmospheric hydrocarbons ( HCs) with a time resolution of 20 min. Of the 50 identified HCs in the rang e C-5-C-10, 15 elute in isolated peaks and 20 in groups of two or more HCs. The remaining 15 HCs suffer from coelution by oxygenated and halogenated c ompounds. Procedures to minimize and quantify the blanks and the memory fro m the adsorbents are described. Calibration was based on a custom-made diff usion source. The accuracy of this calibration (+/-10%, 2 sigma) was verifi ed by analysis of a certified 70-component standard (average deviation: -4. 3+/-2%). During a field experiment in Summer 1998, the HC1010 system was co mpared with a custom-made GC system with cryogenic preconcentration and muc h better separation properties but lower time resolution. In ambient air, g ood agreement (2 sigma deviation <14% or 10 ppt) was found for HCs and grou ps of HCs that are free from coelution with oxygenated compounds, whereas l arge discrepancies (in some cases more than a factor of three) were found f or those HCs that coelute with oxygenated compounds, as identified by MS. A nalysis of the mass spectra from those peaks via specific target ions showe d much better agreement with the FID system of the reference GC within 25%. (C) 2000 Elsevier Science B.V. All rights reserved.