Abstract
A method for the determination of carbonate in sodium hydroxide solution was developed by using a total organic carbon (TOC) analyzer based on combustion-infrared analysis.
The pH of sodium hydroxide solution was adjusted to between 8.0 and 9.2 with 2M ammonium buffer solution (pH 9.0) and hydrochloric acid to avoid loss or uptake of gaseous carbon dioxide. A portion (20μl) of the solution was injected into the TOC analyzer using an automatic sample injector. In the analyzer, the carbonate was converted to carbon dioxide by heating at 900°C in the combustion tube, and the absorbance at 4.3μm was measured and recorded on a chart. A linear relationship was observed between peak height of carbon dioxide and concentration of sodium carbonate in the range of 0-240μg/ml. The relation was applied to the determination of carbonate in sodium hydroxide solution.
The determination limit of the present method was 0.02% as Na2CO3 in sodium hydroxide, about one-tenth of that of the titration method described in JSFA-IV.
