A method for the simultaneous determination of chemical oxygen demand (COD) and inorganic carbon by spectrophotometric and potentiometric (pH) detection, respectively, is described. The carbon dioxide is removed by pervaporation and accepted at the upper part of the separation unit by a buffer stream, the pH change of which is measured by a pH-electrode situated on the top of the unit. The donor stream is, at the same time, led to a spectrophotometer for the measurement of COD. The inorganic carbon is calculated as the difference between the total concentration of CO2 monitored potentiometrically and the COD monitored photometrically. The method was applied to real samples, including paper bleaching liquors, domestic sewage and river water, with good precision. The sampling frequency was 20 h#x2212;1for COD determination and 9 h#x2212;1for inorganic carbon determination.
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