Determination of caffeine content in coffee drinks prepared in some coffee shops in the local market in Jeddah City, Saudi Arabia

Abstract

Abstract The current study was aimed to develop a low cost HPLC method for determination of caffeine content in coffee samples in some coffee shops in Jeddah local market. Caffeine was extracted with water and separated through ZORBAX Eclipse XDB C-18 column using methanol/water (40:60) as mobile phase. The average peak response time for caffeine was 2.747 min with a relative standard deviation of 1.061. The proposed assay was able to detect caffeine in the concentration range from 5 to 45 ppm with limits of detection (LOD = 3σ/b) and quantification (LOQ = 10σ/b) of 1.086 and 3.619 ppm using two-channel UV detector set at 274 and 264 nm with correlation coefficient (R 2) of 0.9996, respectively. The assay was adopted for the determination caffeine content in 30 coffee samples collected from eight brand coffee shops and from local market. Each sample was injected in triplicate (n = 3) and the average and confidence limit of the mean were calculated. The concentration of caffeine in coffee brand shops varied from 513.82 ± \pm 12.91 to 8080.05 ± \pm 3.06 ppm, whereas in beans and instant coffee its content was diverse from 360.18 ± \pm 86.72 to 1306.98 ± \pm 27.31 ppm. These results were validated using Student’s t-test at 95% confidence level.