Heavy metal content of some local spices on the Ghanaian market

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A spice is a vegetable substance of indigenous or exotic origin which is or has a hot, pigment taste, used to enhance taste of foods or to add to them the stimulant ingredients contained in them. They are sparingly used but frequently used in Ghanaian meals. Seven heavy metals were determined in some natural spices on the Ghanaian market. Four of the metals namely zinc (Zn), manganese (Mn), copper (Cu) and iron (Fe) are essential micronutrients and lead (Pb), cadmium (Cd) and mercury (Hg) are toxic metals. A total of eighty three samples comprising of fifteen spices were purchased from seven different markets at Asafo, Takoradi, Kaneshie, Ayigya, Makola and Tema. The spices were processed into the powdered form and subjected to a wet digestion procedure with a mixture of H2O, HCl, HNO3, HClO4 and H2SO4. Sample solutions were analyzed for Hg using a Mercury Analyzer Model HG-5000 and for the other metals using SOLAAR (S Series 711239 v1.23) Flame Atomic Absorption Spectrometer. The range of total Hg concentration (µg/g) for all the spices from all the markets is ND-0.031 (ND- not detectable), that for Cd also ranged from ND- 1.41. The range for Fe is 65.35-221.15, that for Mn is from 14.93-24.96. Zn ranged from ND -17.70 and finally Cu is 4.22-22.91. Pb was not detected in any of the samples analyzed. The amount of spice to be consumed in order to exceed the recommended daily intakes for the metals were calculated based on the recommended daily intake for the various metals. The amounts obtained were not unlikely to be consumed considering how sparingly they are used. Correlation analysis showed strong positive and negative correlation between the metals for the spices.
A thesis presented to the department of chemistry, college of science, Kwame Nkrumah university of science and technology, in partial fulfilment of the requirements for the award of the degree of Master of Science(Environmental Chemistry)