Browsing by Author "Fernandes, S.M.V."
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- Colorimetric determination of phosphorus in milk by flow injection analysis using a thermal/uv induced digestionPublication . Lima, M. J. Reis; Fernandes, S.M.V.; Rangel, António O. S. S.Two flow injection systems for the determination of total phosphorus in milk were developed: one for the determination of phosphorus using offline digestion of milk and another with in-line digestion. The first procedure involves a classical Kjeldahl digestion of milk prior to introducing it into the flow system; the second uses acid, heat and UV-catalysed peroxodisulphate oxidation to convert in-line all forms of phosphorus compounds into orthophosphate, allowing a considerable amount of time to be saved. Concentrations of phosphorus in milk withinthe range of 706 to 984 mg P/L were found and FIA results were in good agreement with those provided by the reference method.
- A sequential injection system for the in-line digestion and colorimetric determination of phosphorus in milkPublication . Lima, M.J. Reis; Fernandes, S.M.V.; Rangel, António O. S. S.A sequential injection analysis (SIA) system involving in-line digestion for the determination of total phosphorus in milk is presented. The developed manifold consists mainly of 2 phases: conversion of all forms of phosphorus into orthophosphates by hydrolysis and oxidation catalyzed by UV radiation (necessary for the efficient oxidation of organic phosphates) and spectrophotometric determination of the phosphomolybdenum blue formed. The proposed method was applied to several cow milk samples and the results were in good agreement with those provided by the reference method, with a maximum relative deviation of 5.2%. The detection limit of the method was around 2 mg P/L with a sampling rate of approximately 17 h−1.