Levels Of Some Heavy Metals And Proximate Analyses Of Cocoa Beans From Eastern And Central Regions Of Ghana.

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In this work total levels of cadmium (Cd), lead (Pb), copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) were determined in order to evaluate the levels of contamination by these metals of dried cocoa beans from the Eastern and Central Regions of Ghana. Fifty (50) samples comprising of twenty five (25) from each Region and an average of five from one community in five different Districts were analyzed using a Buck Scientific Atomic Absorption Spectrometer after aqua-regia digestion at a temperature of 420oC for one hour twenty minutes. The determinations were done at wavelengths of 248.3nm, 324.8nm, 228.9nm, 283.3nm, 279.5nm and 213.9nm for Fe, Cu, Cd, Pb, Mn and Zn respectively. Reliability and accuracy of the results were checked by analyses of two reference materials NBS 1571 SRM certified orchard leaves and IAEA-V-10 SRM certified hay powder. Results obtained from these two certified reference materials showed good agreement with values reportedly contained in them. An average range of 0.030 µg/g-0.079µg/g was detected for Cd, 0.020 µg/g-0.070 µg/g for Pb, 10.742-24.620µg/g for Cu, 14.350-39.820µg/g for Fe, 7.116-18.240µg/g for Mn and 29.620-39.990µg/g for Zn in all the samples. All the samples analyzed were found to contain levels of the heavy metals in question in quantities lower than limits set by Codex Alimentarius of 1.000µg/g for cadmium and lead and levels set by US Environmental Protection Agency (US EPA) and recommended dietary allowance (RDAs) of between 0.900-18.000mg/day for the essential elements set by other reputable institutions. On analyses, the levels of Fe were found to have direct correlation with the age of the cocoa trees from which samples were taken. This made it possible for the age cocoa trees in one of the farms sampled whose age was not available to be predicted. The relationship between iron levels and age can be represented with linear equation with regards to the samples obtained from Asamankese COCOBOD farms. Also the levels of Cu in these samples appeared to have a negative correlation with the age and levels of Fe. Comparing the two Regions, the levels of Fe, Mn, Zn and Pb were found to be higher in the Eastern Region whiles the levels of Cd and Cu were relatively higher in the Central Region than the Eastern Region of Ghana. Proximate analyses was done on the samples obtained from COCOBOD farms at Asamankese in the Eastern Region in order to ascertain their nutritional composition and relate them to age because the ages of five out of the six samples were known. This was done using the compositional analyses of Association of Analytical Chemist (AOAC). The data obtained showed a range of 33.93-39.22% fat, 38.15-40.18% carbohydrate, 13.19-14.42% protein, 2.62-2.70% fibre, 3.19-4.11% ash and 2.58- 5.14% moisture in all the six samples.
A Thesis presented to the Department Of Chemistry in partial fulfilment of the Award Of Master of Philosophy Degree in Environmental Chemistry.