Coprecipitation enrichment-spectrophotometic determination of phosphate ion in sea water

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  • 海水中のりん酸イオンの共沈濃縮‐吸光光度定量法
  • カイスイチュウ ノ リンサン イオン ノ キョウチン ノウシュク キュウコウ
  • 海水中のリン酸イオンの共沈濃縮-吸光光度定量法

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Abstract

New determination procedure of soluble inorganic phosphate in sea water was developed applying the molybdenum blue method of JIS K 0102 Standards. Phosphate ion was enriched by coprecipitation with aluminum hydroxide before the spectrophotometry. In many coprecipitants used, such as magnesium hydroxide, magnesium carbonate, iron hydroxide and aluminum hydroxide, for the process, aluminum hydroxide was the best one as it was filtered easily, gave linear calibration curve and coprecipitated phosphate ion completely. Linear calibration curves were obtained for the phosphate ion solutions of 150, 300 and 1000 ml in volume. Sensitivity of the proposed method was 0.4 ppb of phosphate ion for 0.005 absorbance, when 1000 ml of sample was used. Optimum amount of aluminum sulfate for the coprecipitation of phosphate ion was found to be 20 ml of the 6.5% solution for 1000 ml of the sample. The precipitated aluminum hydroxide should be filtered off within 3 hours. The best acid for the dissolution of the aluminum hydroxide precipitated was sulfuric acid of the concentration higher than 1 N. Effect of co-existing substances such as arsenic, silicon and iron for the analysis was examined. This method was applied to the determination of phosphate in several sea water samples.

Journal

  • BUNSEKI KAGAKU

    BUNSEKI KAGAKU 26 (11), 739-742, 1977

    The Japan Society for Analytical Chemistry

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