Browsing by Author "Gudu, Tsegaye"

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    Determination of Caffeine in Coffee Using Uv/Vis Spectrophotometry
    (Addis Ababa Universty, 2009-07) Gudu, Tsegaye; Redi, Mesfin (PhD)
    Spectrophotometric method was developed for the determination of the amount of caffeine in coffee samples. The Uv/vis spectra of pure caffeine in water and dichloromethane were obtained with peak absorption at λmax 271 and 275 nm, respectively. The developed method showed linearity for the determination of caffeine in the range of 2.5x10-5 mol dm-3 to 1.25x10-4 mol dm-3. The method also showed good precision, accuracy with limits of detection 2.14 and 1.79 mg/l in water and dichloromethane, respectively. The relative standard deviation for the determination of a 2.0x10-5 mol dm-3 caffeine was 4.53% and 3.72% (n=5) in water and dichloromethane, respectively. The molar decadic absorption coefficients of caffeine in water and dichloromethane at maximum wavelength are 1031.2+0.036 and 1004.4+0.029 m2 mol-1, respectively. Analytical parameters were investigated primarily; the method was applied to quantify the amount of caffeine in coffee samples. The method was found to be fast, simple, cost effective and environmental friendly for the determination of caffeine in aqueous solution coffee samples with satisfactory results. Keywords: Coffee Arabica, Caffeine, Absorbance, Uv/vis spectrophotometry, Extraction