Spectrophotometric flow injection determination of total phosphorus in beer using on-line UV/thermal induced digestion |
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Authors: | S M V Fernandes J L F C Lima A O S S Rangel |
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Institution: | (1) Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Rua Dr. António Bernardino de Almeida, P-4200-072 Porto, Portugal e-mail: rangel@esb.ucp.pt, PT;(2) CEQUP/Departamento de Química-Física, Faculdade de Farmácia do Porto, Rua Aníbal Cunha 164, P-4050 Porto, Portugal, PT |
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Abstract: | A flow injection system for the automatic determination of total phosphorus in beer is described. The developed manifold
uses a two-stage photooxidation/thermal digestion procedure together with oxidizing and hydrolyzing reagents to convert all
forms of phosphorus compounds to orthophosphate. Polyphosphates are hydrolyzed by acid and heat, and organo-phosphates are
digested by UV-catalyzed peroxodisulfate oxidation. The orthophosphate formed is then spectrophotometrically determined by
the phosphomolybdenum blue reaction, using stannous chloride as reducing agent. The results obtained for a set of 19 beer
samples (with concentrations from 120 to 735 mg P/L) were in good agreement with the reference method, the maximum relative
deviation found being 4.7%. Relative standard deviations for ten consecutive determinations were lower than 1.5%, and a detection
limit of 1 mg P/L was achieved.
Received: 18 May 1999 / Revised: 5 July 1999 / Accepted: 7 July 1999 |
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