A UV Spectroscopy And GC-MS Method For The Caffeine Determination In Beverage

Caffeine can be applied as an additive in many popular carbonated drinks. People consume caffeine in soft-drink beverages throughout the world. However, the intake of high amounts of caffeine has been shown to produce negative effects on premenstrual syndrome and pregnancy and to promote infertility and cancer. Especially, infants and children should be cautioned not to consume excessive caffeine because of its stimulating effect on the central nervous system and cardiac muscle. Therefore, caffeine analysis is requested to ensure proper caffeine levels in beverages and to meet regulatory standards.A rapid, accurate and organic solvent saving method has been developed for the ultraviolet spectrophotometry (UV) determination of caffeine in beverages. And for the first time, centrifugal extraction procedure with big phase ratio was applied to sample micropreparation prior to instrumental analysis. The method involves the mixing of 100μL sample with 2 mL chloroform and a 3 minute centrifugal extraction procedure in a centrifugal tube. The clear solution obtained was directly determined by UV at wavelength 278 ran. The manipulation was simple, and repeatability of the method was good that the relative standard deviation was less than 3% for the independent measurement. Recovery of the caffeine when added different concentration of standard caffeine solution to three brand beverages was in the range 96.6%～106.1%. A linear calibration curve was generated with caffeine concentration ranging from 0.50～30 mg/L, giving the correlation coefficient as 0.9999. The method provides a 0.001 mg/L detection limit of caffeine. The developed method was applied to determine amount of caffeine in commercial beverages. Good results were received.An automated high-throughput GC/MS method based on single-step spontaneous solvent microextraction was also developed for the direct quantification of caffeine in beverages. With the present method, as little as 25μL of the commercial samples was required to be mixed with 1 mL chloroform in a 2 mL autosampler vial. After 15 minutes spontaneous mixing extraction, the mixture was directly injected into the GC/MS by the autosampler. To obtain the best extraction efficiency for the better quantification and automation, extraction parameters including solvent selection, extraction mode, extraction time, and the ratio of volume between organic acceptor phase and the sample, were optimized. The methodology exhibited excellent linearity between 0.001 and 20 mg/L with the correlation coefficient of 0.9999. The relative standard deviation (RSD) and limits of detection (LOD) of this method were less than 2% and 0.0001 mg/L, respectively. Recovery of the caffeine when spiked to three brand beverages was in the range 99.0%～104.8%. The method developed was simple, accurate, high-throughput, organic solvent saving and could offer automation for batch analysis of caffeine in popular commercial beverage industries.