10-lab-10Spectrophotometric determination of phosphat

10-lab-10Spectrophotometric determination of phosphat -...

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Unformatted text preview: Chem 223: Experiment 10 Spectrophotometric Determination of Total Phosphate in Water Reference 1. Harris. 3rd Edition: Ch. 18, Sect. 2-4 2. Harris. 2nd Edition: Ch. 17, Sect. 2-4 3. Shimadzu Application News- Spectrophotometric analysis. No A 354 4. J, Murphy and J. P. Riley. J. Mar. Biol. Ass. U.K. (1958) 37, 9-14 5. Standard method for the examination of water and waste water (1997). 4500- P- Phosphorous. 6. C. C. Kircher and S. R. Crouch, "KINETICS OF THE FORMATION AND DECOMPOSITION OF 12-MOLYBDOPHOSPHATE," Anal. Chem. 55(2), 242-248 (1983). I. Purpose of the experiment: Phosphorus, widely found in various products such as fertilizer, agricultural pesticides, dyes, processed food, and alkaline detergent, has greatly enriched our lives. However, it also contaminates environmental waters by flowing into rivers and lakes along with residential and industrial waste water, or agricultural runoff. Phosphorous and nitrogen, which enhance the growth of plankton in lakes, are used as indices of eutrophication. Consequently, measurement of phosphorus concentration is important for water quality management. Phosphorus occurs in 3 compounds in natural waters: • inorganic, dissolved ortho-phosphate • dissolved organic phosphorus compounds • particulate phosphorus (bound in biomass or attached to particles), which add up to the total of phosphorus content P-Total, an important parameter in monitoring wastewater treatment plant effluents. In this experiment, students will become familiar with the two standard approaches for the determination of anions using spectrophotometry. II. Introduction There are two common spectrophotometric methods available for determining phosphate or phosphorus concentrations: • Molybdenum blue method • Vanadate/molybdate method (yellow method) Both techniques are based on the measurement of ortho-phosphate. Digestion of both dissolved organic as well as particulate phosphorus compounds is therefore mandatory for determining the total P content. In addition, an unfiltered sample must be acquired in order to include all solid matters in the digestion process. Digestion is usually performed by heating the sample with peroxodisulfate and sulfuric acid....
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This note was uploaded on 02/13/2011 for the course CHEMISTRY 223 taught by Professor Tathithao during the Spring '10 term at Hanoi University of Technology.

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10-lab-10Spectrophotometric determination of phosphat -...

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