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The Development of Iodide-Based Methods for Batch and On-Line Determinations of Phosphite in Aqueous Samples

The Development of Iodide-Based Methods for Batch and On-Line Determinations of Phosphite in Aqueous Samples

Roman A Barco, Deepa G Patil, Weihong Xu, Lin Ke, Crist S Khachikian, Grady Hanrahan, Tina M Salmassi

Talanta. 2006 Jul 15;69(5):1292-9.

PMID: 18970717

Abstract:

Recent developments in the field of microbiology and research on the origin of life have suggested a possible significant role for reduced, inorganic forms of phosphorus (P) such as phosphite [HPO(3)(2-), P(+III)] and hypophosphite [H(2)PO(2)(-), P(+I)] in the biogeochemical cycling of P. New, robust methods are required for the detection of reduced P compounds in order to confirm the importance of these species in the overall cycling of P in the environment. To this end, we have developed new batch and flow injection (FI) methods for the determination of P(+III) in aqueous solutions. The batch method is based on the reaction of P(+III) with a mixed-iodide solution containing tri-iodide (I(3)(-)) and penta-iodide (I(5)(-)). The oxidation of P(+III) consumes free I(3)(-) and I(5)(-) in solution. The remaining I(3)(-) and I(5)(-) subunits are then allowed to react with the amylose content in starch to form a blue complex, which has a lambda(max) of 580 nm. The measurement of this blue complex is directly correlated with the concentration of P(+III). The on-line FI method employs the same reaction between P(+III) and mixed-iodide producing phosphate [P(+V)] that is determined spectrophotometrically by the molybdenum blue method employing ascorbic acid at a lambda(max) of 710 nm. The linear range for both the batch and FI determination of P(+III) was 1.0-50 microM with detection limits of 0.70 and 0.36 microM, respectively. Interference studies for the batch method show that arsenite [As(+III)] and sulfite [S(+IV)] can also be determined by this technique; however, these interferences can be circumvented by oxidizing As(+III) and S(+IV) using KMnO(4) which is an ineffective oxidant for P(+III). Both methods were applied to P(+III) determinations in ultra-pure water and simulated creek water. Results and analytical figures of merit are reported and future work is considered.

Chemicals Related in the Paper:

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AP312692867	3,5-Dichlorophenylzinc iodide solution		312692-86-7	Price

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