Quasi-flow injection analysis for rapid determination of caffeine in tea using the sample pre-treatment method with a cartridge column filled with polyvinylpolypyrrolidone

The sample pre-treatment method using a polyvinylpolypyrrolidone (PVPP) cartridge column combined with a quasi-flow injection analysis (quasi-FIA) system realized the rapid determination of caffeine in three types of tea, green, oolong and black tea. The measurement time for each tea sample pre-treated using a PVPP cartridge column was shortened to 20 s. In the present system, the limits of detection and quantification were 0.3 μM (1.5 pmol injected) and 0.7 μM (3.5 pmol injected), respectively, and a linear calibration curve was afforded up to 800 μM (4 nmol injected). Within-run precision of analysis of standard solutions of 10 and 100 μM caffeine was 0.11 and 0.16% (n = 6), respectively. Between-run precision of analysis of the same solutions over 6 days was 0.78 and 0.74% (n = 6), respectively. Comparison with the conventional HPLC method indicated that the present quasi-FIA method using sample pre-treatment with a PVPP cartridge column was useful for the simple and precise determination of caffeine in green, oolong and black tea samples.