A Simple And Environmental Friendly Method For The Caffeine Determination In Beverage Using GC-MS

Caffeine, a naturally occurring alkaloid found in tea leaves, coffee beans, kola nuts, cacao beans and other plants, is used as a flavoring agent in a variety of beverages, including some soft drinks and energy drinks. The amount of caffeine in soft drinks varies among brands and it is closely regulated by FDA to no more than six mg per fluid ounce or 200 mg L^-1. Therefore, caffeine analysis is required to insure proper caffeine levels in beverages to meet regulatory standards. Method that are simple, rapid and can greatly reduce the need of organic solvent for the analysis of caffeine in beverages, therefore, are desirable, particularly for the quality control applications and to satisfy regulatory requirements for products.In this thesis, a simple, quick and organic solvent saving procedure has been developed for the GC-MS determination of caffeine in beverages. 25μL sample was first mixed with 1 mL ethyl acetate by ultrasonic shaking for 2 min followed by a desiccation procedure with 0.0500 g magnesium sulfate for 3 min in a 1.5 mL autosampler vial and then directly analyzed by GC-MS.A linear calibration curve was generated with caffeine concentration ranging from 0.005 to 30.0 mg L^-1. The procedure developed provides a limit of detection of 0.001 mg L^-1 of caffeine in the final solution for a sample injection of 1 uL. The reproducibility of the method was measured by triplicate inter-day analysis of soft drink of different brands and by five independent intra-day analysis of a sample at concentration of 95.7 mg/L. The relative standard deviation was less than 2 % for independent inter-day assays and 0.91 % for five independent intra-day assays. The accuracy of the current method was validated through the direct comparison of quantitative results of three kinds of beverage by the procedure developed with those reported in previous studies and declared by USA National Soft Drink Association. Good agreements with two values were found. The accuracy of the method was further validated through recovery studies of caffeine concentrations ranging from 25.0 to 200 mg L^-1. 50.0, 100, 150 and 200 mg L^-1 caffeine standard solutions were added to real samples of soft drinks of different brands and determined by the method developed. It provided recovery percentage values from 98.8 % to 104.4 %.The procedure developed in this thesis is simple, accurate, the total organic solvent need for this procedure is 1 mL per sample. All this advantages enable it to be a potential and valuable tool to determine caffeine in beverages for regulatory requirements as well as for the rapid industrial content assessment of caffeine.