Test composition, device and method for the colorimetric determination of phosphorus
AssigneeEnvironmental Test Systems, Inc.
InventorsYuriy Vladimirovich Evtodienko, Michael Allen Van Lente
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Abstract
A unitized, one step test reagent composition, device and method is presented for the determination of phosphorus in various test sample fluids such as soil extracts. The invention is a modification of the Murphy and Riley methodology which utilizes a molybdate salt and a reducing agent to generate "molybdenum blue" in the presence of phosphate. In addition to the molybdate salt, the test reagent composition includes a chromogenic reducing agent which contributes to the color development and a solid buffer. The composition is preferably incorporated into a matrix such as paper for ease of handling.
Claims18
A test device for the determination of inorganic phosphorus in aqueous test samples comprising a porous absorbent matrix incorporated with the dry residue of a reagent composition comprising:
- A. an effective amount of a molybdate salt capable of reacting with any inorganic phosphorus present in the aqueous test sample to form 12-molybdophosphoric acid;
- B. a solid buffer system capable of maintaining the test composition in a pH range of about from 0.3 to 3.0 when the matrix is contacted with the aqueous test sample;
- and,
- C. an effective amount of a chromogenic material capable of reducing the 12-molybdophosphoric acid to a molybdenum blue complex, the oxidized chromogenic material and the molybdenum blue together forming a complex chromophoric product in an amount proportional to the amount of phosphorus in the aqueous test sample.
A method for the determination of inorganic phosphorus in aqueous test samples, said method comprising:
- A. Contacting the test sample with a test reagent composition comprising a molybdate salt, a solid buffer for maintaining the mixture of test sample and reagent composition in a pH range of about from 0.3 to 3.0, and a chromogenic reducing material to produce a colored reaction product consisting of molybdenum blue and the oxidized form of the chromogenic reducing material;
- B. Measuring the amount of color produced by the reaction of the test reagent composition with the phosphorous in the test sample;
- and,
- C. Converting the measured amount of color produced to concentration of inorganic phosphorus in the test sample.
Dependencies are inferred from the claim text.