The properties of chromatomembrane cells in flow systems coupled to gas chromatography - analysis of volatile organic compounds

The economical use of modern analytical instrumentation requires an online- coupling of efficiently working flow-systems which automate both sampling a nd sample pretreatment. Whenever extraction and preconcentration procedures are necessary the application of chromatomembrane cells proved to be very worthwhile. On this occasion the analyte exchange takes place inside a bloc k of biporous PTFE wherein the two immiscible phases come into contact with each other. A special enclosure enables water and the extracting nitrogen to flow independently through that block. In case of gaseous extractants th e behavior of the biporous PTFE and its mechanical parameter have to be inv estigated precisely in order to overcome the special problems of trace anal ysis in gases. The gas-chromatographic detection of volatile organic compou nds (VOC's) requires a discussion on the effects of gas-sorption and the ki netics of equilibration which should be taken into consideration for using the chromatomembrane cell as an extractor from waste water. The investigati on realizes at least that a quick pretreatment is made possible and, howeve r, sample sizes decrease remarkably in comparison with competing methods as head space analysis or purge and trap technique. The application of chroma tomembrane cells permits reasonable accuracies with a limit of detection on the ng/l level. (C) 2000 Elsevier Science B.V. All rights reserved.