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Development of a new method for direct measurement of p CO 2 in natural waters
Author(s) -
Che Guangwei,
Ilmberger Johann
Publication year - 1994
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1994.39.4.0976
Subject(s) - silicon rubber , analytical chemistry (journal) , natural rubber , conductivity , silicon , detection limit , ion exchange , electrical resistivity and conductivity , chemistry , ion , materials science , environmental chemistry , chromatography , physics , composite material , organic chemistry , quantum mechanics
A new direct measurement method for p CO 2 in water samples is presented. The technique is based on the fact that the dissolved CO 2 in a water sample is able to diffuse through the wall of a thin silicon rubber tubing, whereas the dissolved ions remain. The CO 2 passing through the wall is equilibrated with the deionized water flowing inside the tubing, and its electric conductivity is measured by a conductivity flow cell afterward. Laboratory experiments on 255 CO 2 standard samples with p CO 2 varying from 300 to 30,000 ppmv show a mean CO 2 exchange ratio R across the silicon rubber membrane of 0.95, with SD = ±0.04. For p CO 2 in the 40–300 ppmv range (40 CO 2 ‐standard samples), a mean exchange ratio R = 0.93±0.09 has been determined. The detection limit of this method is 0.6 µ M (∼18 ppmv at 25°C).