電量検出器を用いるイオン排除クロマトグラフ法による金属工業排水中のフッ化物イオンの定量

Determination of fluoride ion in metal industry wastewaters by ion-exclusion chromatography with coulometric detection.

Tanaka Kazuhiko

分析化学

溶離液としてメタノール-水を用いるH+型陽イオン交換樹脂におけるイオン排除クロマトグラフ法により, 金属工業排水中のF-を定量した. 分離カラムから溶出したF-は, フッ化水素として導電率検出器及びH+が検出できる電量検出器(H+とp-ペンゾキノンの問の定電位電解反応)によりモニターした. 水溶離液を用いたとき, 強酸性陰イオン(Cl-)からのF-の分離は不完全であったが, 40%メタノール-水を用いる溶離により, 両者は完全に分離できた. メタノール-水を用いる溶離における両検出器応答の減少の程度は, 電量検出器のほうが小さかった. フッ化水素は弱酸であるため, 導電率検出器による検量線は非直線性を示したが, 電量検出器によるそれは少なくとも100ppmまで良好な直線性を示した. 以上の結果は, イオン排除クロマトグラフ法においては電量検出器が有効であることを示した. 本法により, アルミニウム精錬工業及びめっき工業排水中のF-の定量は, 良好に達成できた.

The ion-exclusion chromatography with a cation exchange resin (H+-form)using methanol-water mixture as an eluent was investigated for the determination of F- in several metal industry wastewaters. Fluoride ion eluted from the column was monitored with conductometric detector (COND) and flow coulometric detector (FCD) based on the electrochemical reaction of Ht ion from HF with p-benzoquinone at a constant applied potential (+0.45 V vs. Ag-AgI) . The retention volume (VR) of F- increased with increasing the concentration of methanol in the eluent, and that of very weak acid anion (HCO3-) decreased. Furthermore, the VR of strong acid anion (CI-) did not vary and corresponded to the column void volume. Thus, quantitative separation of F-from CI- and HCO3- was accomplished by elution with 40% (v/v) methanol-water. The COND responses of Cl-, F-, and HCO3- remarkably decreased with increasing the concentration of methanol. The FCD responses of Cl-, F-, and HCO3- did not remarkably decrease in comparison with the results obtained with the COND under the same elution conditions. This is most striking characteristics of the FCD. The calibration graph for F- obtained with the COND showed a nonlinear because of low dissociation at higher concentrations. However, the good linear relationship was obtained under the concentration range (5~100) ppm of F- with the FCD. Therefore, it is recommended to use the FCD in this method. The present method was applied to the determination of F- in several actual samples with satisfactory results.

ion-exclusion chromatography with coulometric detection

cation exchange resin (H+-form)

determination of F- in metal industry wastewaters

methanol-water eluent

Chemistry [ 430 ]

jpn

日本分析化学会

[ISSN] 0525-1931

[NCID] AN00222633