By acidifying a sample containing a dissolved inorganic carbon (DIC) carbon dioxide is formed that passes across a gas-permeable membrane into a acceptor stream containing bromothymol blue in basic (blue ) form. (A). Collection of CO2 in acceptor solution decreases pH, and the color change (to yellow) monitored by optical fibers at 480 nm, is proportional to the initial DIC content in the sample. By sequencing 100 mcrL of sample, and 100 mcrL 0.1 M H2SO4 into holding coil, followed by flow reversal of 200 mcrL that positions the reaction mixture into the sensor the reaction rate stopped flow measurement was carried out. Using a stop flow period of 120 two concentration ranges were investigated:
Carbon Speciation by Gas Sensor – LOV
2.3.30.
- Blank, 1,2; 6; 12; 60; and 129 ppm C (B)
- Blank, 12; 18;24;30 and 36 ppm C (C)
As expected the calibration curve was linear in the narrow calibration range, as implied in the colored bars on right.
