DETERMINATION AND COMPARISON OF Si, Na, Cu, Ni, AND Co CONTENTS OF GARDEN COFFEE AND MODERN FARM COFFEE OF ABAYA DISTRICT, WEST GUJI ZONE, OROMIA REGION OF ETHIOPIA

<strong>ABSTRACT</strong>: The concentrations of five metals (Na, Cu, Ni, Co and Si) were determined in coffee bean that cultivated in Garden and Modern farm method that obtained from Abaya District by using Inductive coupled plasma-optical spectrometry, Optima 8000 (ICP-OES). The digestion procedure was carried out using 5 mL of HNO3 and 5 mL of HClO4 with 3 hours total time at temperature about 120 oC for digestion of 0.5 g of powder sample of both coffee farms. The validity of the optimized procedure was evaluated by the analysis of spiked samples whose recovery of analytes was in the range of 85−113 %. The mean concentration of each metal in the two farms of coffee bean samples was Na (192.23, 193.20mg/l), Cu (4.86, 8.33mg/l), Co (0.63, 0.99mg/l) and Ni (0.44, 1.76mg/l) Garden coffee and Modern coffee farms respectively but, Si is under the detection limit. The metal concentrations of the modern coffee farm were higher than those of garden coffee farm, when expressed in the same units. The extraction was highest for Na and intermediate for Cu lowest for Co and Ni. The concentrations of metals in the garden coffee farms were compared to the values modern coffee farms that the concentration of Modern coffee is relatively higher than the Garden coffee farms.