COMPARATIVE STUDY OF WET DIGESTION METHODS OF SAMPLE PREPARATION FOR ELEMENTAL ANALYSIS.

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Date
1984-02
Authors
AJIBOLA, VICTOR OLATUNJI
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Abstract
Nine wet digestion methods were used on two guava samples and eight tomatoe samples for the purpose of elemental determination. These samples "belong to the group of fruity vegetables. Acid and acid mixtures were used to digest the samples; these include HNO3., HNO3/H2SO4, , HNO3/HC104, HN03/HC104/H2S04 , HN03/NH4 N03, and HCl/HNO3. Selenium was used as a catalyst in one of the procedures. Eleven metals were determined. These are sodium, potassium, calcium, magnesium, iron, zinc, copper, manganese, lead, cobalt, and cadmium. Atomic Absorption spectrophotometry and flame photometry were used to determine the metals. The reliability of each digestion method, for the determination of each, metal in each sample was assessed, by calculating the mean and standard deviation, and by performing the multiple range tests on the result of each method. It was found that, no one single method of digestion could release all the metals of interest quantitatively and reliably from each sample. A minimum of three digestion methods for each sample was found tt be needed for the determination of these metals, each method being reliable for a group of metals. Some methods such as these involving the use of perchloric acid in the digestion mixture and those using nitric acid alone were found to lead to partial or total losses in certain trace elements like Co, Cd and Pb. The three most valuable digestion methods that are recommended for the types of biological samples studied are method A (H2SO4/HNO3), method B (modification of A), method F (HNO3/NH4N03).
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A thesis submitted to the Postgraduate School, Ahmadu Bello University, in partial fulfilment of the requirements for the degree of MASTER OF SCIENCE IN ANALYTICAL CHEMISTRY Department of Chemistry Faculty of Science, Ahmadu Bello University, Zaria.
Keywords
WET DIGESTION,, ELEMENTAL ANALYSIS,
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