Determination of total carbon dioxide in seawater by capillary type isotachophoresis

Abstract

A new analytical procedure for total carbon dioxide in seawater was developed: a capillary-type isotachophoresis which applied a tubular microporous PTFE membrane as a preliminary enrichment was used. Carbon dioxide was generated by adding sulfuric acid to seawater samples, permeated through a tubular microporous PTFE membrane and dissolved in sodium hydroxide solution for the separation from large amounts of coexisting anions, such as chloride and sulfate ions. A linear working curve was obtained for artificial seawater samples containing up to 40 mg/l of total carbon dioxide. The proposed method was applied to the determination of total carbon dioxide in surface and bottom seawater samples. Concentrations of the total of free carbon dioxide and carbonic acid, hydrogencarbonate and carbonate ions in these samples were calculated from the concentration of total carbon dioxide, temperature, pH and salinity of samples measured in situ.