COLORIMETRIC DETERMINATION OF SOME TRANSITION METALS IN SELECTED INI-ANT MILK FORMULAE.

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Date
1997-11
Authors
CHIME, CHARLES CHUKWUMA
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Abstract
Infant formulas were digested with nitric acid and sulphuric acid (5:1); furnace ashed at 500 ± 10°C; and treated with 10% solution of trichloroacetic acid (TCAA). The resulting concentrates were analyzed colorimetrieally for iron, using 1,10-phenanthroline, and 2,2'- Bipyridyl as ligands; 2,9-dimethyl-1,10-phenanthroline for copper; Dithiozone in carbontetrachloride for zinc; Potassium periodate for manganese; Nitroso-R-salt for Cobalt; and Dithiozone for Lead. Atomic Absorption Speetrophotometric (AAS) analyses of the metal ions in the three sample preparations were also done. Most coexisting metal ions found to interfere were conveniently masked prior to the determination. Recoveries of added ion for each of the metal ions were investigated colorimetrically using the three preparations. On statistical comparison of the results obtained from the colorimetric methods with the standard (AAS) method, the accuracy and acceptability of the colorimetric methods were assessed. Six organic reagents namely: Benzidine, 1,2,3-trihydroxylbenzene (Pyrogallol), Rodizonic acid, Flourescien, Picric acid, and Mercaptoethanol were tested for their colored complex formation with iron, copper, zinc and manganese. Pyrogallol found to form stable complex that could enable the colorimetric determination of iron, was exploited in estimating iron in the sample preparations. The results obtained were acceptable and relate well with the AAS method. Other essential parameters in infant formula were determined and compared statistically with the values displayed by the manufacturers. It was found that only the results for copper, zinc and manganese compared very well with the manufacturers values. The results for the other parameters varied from sample to sample.
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A THESIS SUBMITTED TO THE POST GRADUATE SCHOOL, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF MASTER OF SCIENCE IN ANALYTICAL CHEMISTRY DEPARTMENT OF CHEMISTRY FACULTY OF SCIENCE, AHMADU BELLO UNIVERSITY, ZARIA - NIGERIA NOVEMBER, 1997.
Keywords
COLORIMETRIC,, DETERMINATION,, TRANSITION METALS, INI-ANT MILK FORMULAE.
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