間接吸光検出イオンクロマトグラフィーによる河川水中の塩化物イオン,硫酸イオン及び硝酸イオン定量のためのベンゼンカルボン酸誘導体の分離能の比較

吸光光度検出器を用いたイオンクロマトグラフィーによる河川水中の塩化物イオン,硫酸イオン及び硝酸イオンの分析を目的とし本研究を行った.溶離イオンとして,2価,3価及び4価のベンゼンカルボン酸誘導体を比較した.河川水に含まれる程度の塩化物,硫酸,硝酸イオンの定量のためにはトリメリテートイオン(1,2,4-ベンゼントリカルボン酸イオン)が有用であることが分かった.陰イオン交換カラム(TSK gel IC-Anion-PW,4.6mmi.d×50mm)を用いることにより,塩化物,硫酸,硝酸イオンを約4分で分離定量できた.検量線は塩化物イオン(0.8~10)×10(-4)M,硫酸イオン(4.4~4)×10(-4)M,硝酸イオン(0.1~20)×10(-4)Mの範囲で良好な直線となった.普通河川水中に存在する程度のイオソは定量を妨害しない.再現性は各イオンとも相対標準偏差で1.5%以内であった.検出限界は塩化物イオン0.1ppm,硫酸イオソ0.2ppm,硝酸イオン0.1ppmであった.実際試料(河川水,水道水)に応用し,満足のいく結果を得た.

Rapid and sensitive determination of chloride, sulfate and nitrate ions in river water was achieved by ion chromatography with UV photometric detector. Comparison of elution ability of eluent ions was made by using phthalate, hemimellitate, trimellitate, trimesate and pyromellitate ions at pH 7.5. Trimellitate solution (1,2,4-benzenetricarboxylate, 4×10(-4) M) is superior to other eluent ions because of its strong light-absorption at longer wavelength beyond 250 nm, suitable ability of elution for chloride, sulfate and nitrate ions, low price, high purity and easy availability. An anion exchange column (TSK gel IC-Anion-PW, 4.6 mm i.d.×50 mm) was used. Twenty microliters of sample solution was injected and decrease in absorbance of the trimellitate eluent at 250300 nm was detected. The calibration curves were linear in the range of (0.810)×10(-4) M for chloride, (0.44)×10(-4) M for sulfate and (0.120)×10(-4) M for nitrate. By the proposed method, chloride, sulfate and nitrate in river water were determined within four min. The relative standard deviations of ten measurements of tap water were 0.35% for chloride, 0.56% for sulfate and 1.3% for nitrate, respectively.