COULOMETRIC TOTAL CARBON-DIOXIDE ANALYSIS FOR MARINE STUDIES - MAXIMIZING THE PERFORMANCE OF AN AUTOMATED GAS EXTRACTION SYSTEM AND COULOMETRIC DETECTOR

A global survey of the distribution of dissolved CO2 taking advantage of sampling opportunities provided by the World Ocean Circulation Expe riment: World Hydrographic Program (WOCE-WHP) is being carried out thr ough 1995. Goals include the measurement of oceanic inorganic carbon t ransport and the development of a data base from which future fossil-f uel CO2 build-up can be monitored. The analytical method selected for total carbon dioxide (C-T) is gas extraction of acidified seawater wit h coulometric titration of the acid formed by the resultant carbon dio xide and monoethanolamine. To combine high accuracy and precision (+/- 1.5 mu mol/kg for C-T greater than or equal to 2000 mu mol/kg) with a high rate of analysis, we have modified an automated single-parameter system. Following prototype development between 1987 and 1990, an inst rument emerged with the acronym SOMMA Standing for single-operator mul tiparameter metabolic analyzer. Improved functional and operating proc edures have integrated electronic calibration, CO2 gas calibration, an d sample analysis with automated pressure, temperature, and conductivi ty (salinity) sensing into a single convenient transportable package.