Automatic coulometric titration with photometric end-point detection : Part II. Coulometric Determination of Nanomole Amounts of Carbon Dioxide by non-aqueous titration

Abstract

An improved coulometric method for the determination of carbon dioxide by nonaqueous titration is described. A titration efficiency of 100 ± 0.1% was obtained with a large generating cathode in 0.1 M potassium perchlorate solution containing 12.3 ml of dimethylformamide, 0.3 ml of monoethanolamine and 0.025 ml of an indicator solution containing 1.5 mg of thymolphthalein per ml of n-butanol. The anodic and cathodic compartments were separated by a glass membrane in contact with an ion-exchange membrane. The lowest amount of carbon dioxide which could be determined with a relative standard deviation of 10% was 0.5 nmol. Compared with other titrimetric methods, this sensitivity constitutes an improvement of about two orders of magnitude.