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Determination of nitrate and nitrite in dairy samples by sequential injection u...
Lima, M.J. Reis; Fernandes, Sílvia M.V.; Rangel, António O.S.S.A sequential injection analysis (SIA) system for the spectrophotometric determination of nitrate in dairy samples was developed. A test portion was aspirated into a carrier solution containing ethylendiaminetetracetic acid (EDTA) and ammonium buffer, which flowed into a copperized cadmium reduction column installed in-line for the determination of the nitrate plus nitrite contents of samples. For the nitrite de...
A flow system for the spectrophotometric determination of lead in different typ...
Mesquita, Raquel B.R.; Fernandes, Sílvia M.V.; Rangel, António O.S.S.A flow system for the spectrophotometric determination of lead in natural and waste waters is proposed. The determination is based on the colorimetric reaction between malachite green and iodide, followed by the formation of a ternary complex between those reagents and lead cations. The developed flow system includes a lead pre-concentration step in a column packed with a cationic resin (Chelex 100) operating i...
Sequential injection titration of chloride in milk with potentiometric detection
Lima, M.J. Reis; Fernandes, Sílvia M.V.; Rangel, António O.S.S.In this work, a sequential injection system for the pseudo-titration of chloride in milk is described. Milk was directly aspirated into the system and sandwiched between two silver nitrate plugs (titrant). The aspirated zones were then propelled to the detector (Ag2S/Ag tubular electrode), where the depletion in the titrant silver concentration (due to the formation of a AgCl precipitate) was monitored. The res...
Turbidimetric determination of chloride in different types of water using a sin...
Mesquita, Raquel B. R.; Fernandes, Sílvia M. V.; Rangel, António O. S. S.A sequential injection analysis system for the turbidimetric determination of chloride in different types of water is proposed. The determination is based on the reaction of chloride with silver ions and the subsequent measurement of the turbidity caused by silver chloride precipitation. In this method, the use of toxic reagents, such as mercury thiocyanate, commonly employed in most spectrophotometric techniqu...
Spectrophotometric flow injection determination of total phosphorus in beer usi...
Fernandes, Sílvia M. V.; Lima, José L. F. C.; Rangel, António O. S. S.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 oxida...
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