水素型陽イオン交換樹脂を用いるリン酸, 亜リン酸, 次亜リン酸各イオンの電量検出型イオン排除クロマトグラフィー

Ion exclusion chromatography of phosphate, phosphite and hypophosphite ions on a hydrogenform cation exchange resin with flow coulometric detection.

Tanaka Kazuhiko

Sunahara Hiroshi

分析化学

対応する酸が接近した第1次解離定数(pK1)を有するリン酸, 亜リン酸, 次亜リン酸各イオンを, 水素型陽イオン交換樹脂を用いてイオン排除的に分離するために, カラム温度, 溶離液組成(水と有機溶媒及び過塩素酸の混合系)を検討した.

水溶離液を用いた場合, 各リン酸イオンはその対応する酸が接近したpK1(約2, 18℃)であるため接近したキャパシティー比(k')を示したが, カラム温度の上昇, メタノール, エタノール及びアセトン添加により溶離液の誘電率が低下してpK1が増大する結果, これらリン酸イオンの溜は増大した. 各リン酸イオンのk'は0～80%(v/v)のアセトンにおいてその濃度の増大とともに直線的に増大し, 同様に(25～80)℃のカラム温度においてその温度の上昇とともに直線的に増大した.

カラム温度50℃, 溶離液70%(v/v), アセトン(1ml/min)の分離条件下でこれらリン酸イオンの混合物は完全分離できた.

一方, 各リン酸イオンの電解効率は0～80%のアセトン溶離液においてその濃度の増大とともに低下し, その程度は次亜リン酸, 亜リン酸, リン酸各イオンの順であった.

In the separation and indirect detection of phosphate, phosphite and hypophosphite in a mixture by ion exclusion chromatography with a hydrogen-form cation exchange resin, a flow coulometric method was used for the detection of hydrogen ion liberated by cation-exchange. The chromatographic conditions such as the composition of an eluent containing organic solvents and column temperature were investigated. For a water eluent, the capacity factor (k') of these anions were 0.051 for phosphate ion, 0.018 for phosphite ion and 0.038 for hypophosphite ion, respectively, and depended on the, first dissociation constant (pK1) of the corresponding acid. For the eluent of water-organic solvents or water-perchloric acid, the k' of these anions increased with decreasing dielectric constant of the eluent caused by the addition of organic solvents, such as methanol, ethanol and acetone. The increase of k' occurred also by the addition of perchloric acid. For the water-acetone eluent, the logarithm of k' of these anions increased linearly with the increase in the acetone concentration from 0 to 80%(v/v) and the increase in column temperature from 25 to 80°C. Each electrolytic efficiency of these anions obtained from the chromatogram peak area decreased with increasing acetone concentration, being 90% for hypophosphite ion, 57% for phosphite ion and 50% for phosphate ion, respectively, under the conditions of the 80% (v/v) acetone and flow rate of 1 ml/min. The separation of a mixture of these anions can be best achieved by elution with 70% (v/v) acetone at 50 °C.

Cation exchange resin

Flow coulometry

Hypophosphite

Ion exclusion chromatography

Phosphate

Phosphite

Chemistry [ 430 ]

jpn

日本分析化学会

[ISSN] 0525-1931

[NCID] AN00222633