Simultaneous determination of silicate and phosphate in environmental waters using pre-column derivatization ion-pair liquid chromatography |
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Authors: | Yukio Yokoyama Takenobu Danno Mizuki Haginoya Yukari Yaso Hisakuni Sato |
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Institution: | Department of Analytical Chemistry, Faculty of Engineering, Yokohama National University, 79-7 Tokiwadai, Hodogaya, Yokohama 240-8501, Japan |
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Abstract: | A highly sensitive HPLC method for the simultaneous determination of soluble silicate and phosphate in environmental waters was developed, using ion-pair liquid chromatography preceded by the formation of their yellow α-heteropolymolybdates. The moderate-pH mobile phase enabled to use a highly efficient reversed-phase silica column. The pre-column coloring reactions at moderate-pH were reproducible for both silicate and phosphate in all quantification ranges with R.S.D.s less than 2% and 5%, respectively. The linear calibration lines between concentrations (mg-SiO2/L and mg-PO4/L) and peak area intensities were obtained for silicate and phosphate both with acceptable determination coefficients (r2) of 0.9999. The limits of determination for both analytes were 0.007 mg-SiO2/L and 0.003 mg-PO4/L, which were calculated theoretically using 10σ/slope. The four-digit dynamic ranges were obtained for 0.007-10 mg-SiO2/L and 0.003-20 mg-PO4/L. The developed method was applied for the analysis of tap water, river water, coastal seawater, well water, hot-spring water, commercial mineral water, and laboratory water. The results were very reasonable and acceptable from the environmental viewpoints, which were well correlated with those confirmed by the molybdenum-blue spectrophotometry. |
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Keywords: | Simultaneous determination Silicate Phosphate Yellow α-heteropolymolybdates Pre-column derivatization Ion-pair HPLC |
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