Simple and Rapid UV Spectrophotometry of Caffeine in Tea Coupled with Sample Pre-treatment Using a Cartridge Column Filled with Polyvinylpolypyrrolidone (PVPP)

抄録

We have applied a sample pre-treatment method with a cartridge column filled with polyvinylpolypyrrolidone (PVPP) to the effective removal of polyphenols and simple UV spectrophotometry of caffeine in tea. The absorption maximum length (λ_max) for caffeine was close to those for tea catechins in aqueous 1% acetic acid; therefore, the UV spectrum of a non-treated green tea sample had a large absorption wave. In contrast, the absorbance of the green tea sample was gradually reduced by PVPP cartridge treatment using PVPP from 0 to 50 mg, and was nearly constant using a pre-treatment cartridge with more than 100 mg PVPP, because tea catechins were effectively removed and caffeine was mostly recovered from a green tea sample by means of PVPP cartridge treatment. The PVPP pre-treatment cartridge also removed polyphenols successfully from oolong and black tea samples. Comparison with conventional HPLC analysis indicated that the present pre-treatment method with a PVPP cartridge was useful for the simple and selective UV spectrophotometric determination of caffeine in green, oolong and black tea samples.