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KMID : 1024520010100010013
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Journal of the Environmental Sciences
2001 Volume.10 No. 1 p.13 ~ p.19
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Automated On-Line Digestion System for the Determination of Total Phosphorus
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Chung Hyung-Keun
Cho Young-Il
Kim Burm-Shik
Park Ju-Hyung
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Abstract
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An on-line digestion system based on the flow injection analysis technique was presented for the determination of total phosphorus. The system converts condensed and organic phosphoruses into orthophosphate that can be analyzed spectrophotometically. The reaction between orthophosphate and ammonium molybdate in a strong acid medium forms the yellow complex of phosphomolybdate which is next reduced to a molybdic blue complex by stannous chloride. The quantitation of orthophosphate is based on the absorbance of the molybdic blue. To determine total phosphorus, the digestion system was installed between the sample injector and the reaction coil with the added lines of digestion solution(potassium persulfate+sulfuric acid) and the carrier. The system has shown that the digestion efficiencies were greater than 95% for the typical condensed and organic phosphoruses. When tripolyphosphate standards were used, the calibration data showed that the linear dynamic range extended to a concentration of 1.5ppm with the detection limit of 25ppb total phosphorus. The typical relative standard deviation was less than 2%. The proposed system was successfully applied to lake water, wastewater, and streamwater. The analytical variables such as digestion efficiency, analysis time, and reproducibility were evaluated and compared with the manual digestion method.
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KEYWORD
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On-line digestion system, Flow injection analysis, Total phosphorus, Orthophosphate, Detection limit
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