Solutions required
1. Provided
1.1 Caffeine working standards (20, 40, 60, 80, and 100 ppm)
1.2 Leaf tea samples
1.3 Mobile phase (HPLC grade, degassed) (Acetonitrile:Tetrafluoroacetic acid = 87:13)
2. To prepare
3.1 Tea solutions (see procedure)
3.2 Boiled water