This work is an example of multi parameter SI system, designed to carry out gas diffusion, sample pretreatment and detection within a single manifold.
Carbon speciation in inland bathing waters was developed by designing a sequential injection system that accommodated all carbon related species. This unique flow system performed the determination of dissolved inorganic carbon (DIC), free dissolved carbondioxide (CO2), total carbon (TC), dissolved organic carbon and alkalinity. The determination of DIC, CO2 and TC was based on color change of an acid/base indicator, the bromothymol blue monitored at 660 nm, when acidified by CO2 generated in the gas diffusion unit (GDU) , furnished with a hydrophobic membrane.
For the DIC determination, the sample was acidified by the donor stream before entering the gas diffusion unit. Fror the the TC determination, an in-line UV photo-oxidation of the sample was carried out first in order to convert all carbon species into CO2. Dissolved organic carbon (DOC) was determined by subtracting the obtained DIC value from the TC obtained value.
The determination of alkalinity was based on the spectrophotometric measurement of bromocresol green color change monitored at 611 nm. A complete analytical cycle took about 5.5 min for the simultaneous determination of DIC and TC, as for the combined determination of CO2 and alkalinity a complete cycle took about 3.3 min which is a substantial improvement compared to existing methods.
Carbon Speciation in Natural Waters
2.3.31.
