重炭酸塩の自動電量逆滴定分析法の検討

Evaluation of an Automated Coulometric*1 Back-Titration Analysis of Bicarbonate

　はじめに―二酸化炭素含量は多くの方法で測定されてきた．初めはガス分析法で測定された．その方法では酸の添加，CO₂の真空抽出ならびに容量分析的または圧分析的にCO₂測定を行った．AutoAnalyzer法はCO₂含量の自動定量法である．この方法では，酸を添加し放出されるCO₂をフェノールフタレインを含有するアルカリ緩衝液で吸収し，吸光度の減少を測定する．その他のCO₂含量測定法としては二酸化炭素圧（pCO₂）電極の利用がある．pCO₂は試料のCO₂含量に比例する．

Introduction―Carbon dioxide content has been measured in many ways. Originally, it was measured gasometrically.^*2 This involved the additio of acid, vacuum extraction of CO₂, and measurement of the CO₂ volumetrically^*3 or manometrically.^*4 The AutoAnalyzer^®*5 method offers an automated method for the determination of CO₂ content. In this method acid is added, the CO₂ that is released is absorbed by an alkaline buffer containing phenolphthalein, and the decrease in absorbance is measured. Still^*6 another method for the determination of CO₂ content is the use of the carbon dioxide pressure (pCO₂) electrode. The pCO₂ is proportional to the CO₂ content of the sample.