The Use of Automated “On Line” Gaschromatrography for the Monitoring of Organic Trace Gases in the Atmosphere at Low Levels

Abstract

The usual procedure for measurements of hydrocarbons, halocarbons, and similar trace gases in the atmosphere is sample collection in the field and subsequent analysis in the laboratory. However this procedure is not adequate if intensive field investigtions with a high measuring frequency are desired. In this case the use of in-situ measurement techniques is necessary. For the measurement of volatile organic trace substances in the atmosphere the by far best technique is gaschromatography. However even if very sensitive ionization detection is employed, a preconcentration step is necessary if the technique is to be used at low pollution levels. In this paper the basic design and some applications are described for an automated gaschromatograph suitable for unattended operation. The instrument allows automated prconcentration of the ambient air sample, injection etc. including calibration with an external standard. The lower limits of detection are in the ppt range, the reproducibility of the measurements better than 10%. Some examples for results obtained with this instrument are presented.