DETERMINATION OF CO2 IN GASEOUS SAMPLES USING A MONOSEGMENTED FLOW SYSTEM AND CONDUCTIMETRIC DETECTION

The monosegmented approach to flow analysis was employed for determina tion of low contents (100-1000 ppmv) of CO2 in gaseous samples. The fr ont bubble of the flow pattern constitutes the gaseous sample. The sam ple is pumped through a glass tube (2 mm i.d., 80 cm long) by deionise d water. The film of water present in the tube wall absorbs the CO2 pr esent in the sample. The liquid monosegment collects, by convection mo vement of the fluid, the layer containing the partially ionized CO2, w hile the second bubble restricts the dispersion of the collected speci mens. The conductivity of the liquid monosegment is monitored at the e nd of the glass tubing and is proportional to the CO2 content in the g aseous sample. The system has been optimized for determination of CO2 in the 50-1000 ppmv range. For the experiment, 100 mu l of sample is e mployed and the system can perform 60 determination per hour. The rela tive standard deviation for the signals of standards in the 100-900 pp mv range was ca. 3%. Comparison with a gas chromatographic method reve aled a mean relative difference of 7% for samples containing CO2 in th e 20-700 ppmv range. Toe system employing conductimetric detection doe s not employ any reagent, is very simple and suitable for field monito ring of CO2 present in the atmosphere, indoors and outdoors. (C) 1998 Elsevier Science B.V.