A sample from each pack of products was
weighed and boiled in 150 mL of water. Then, 2 mL of
sample solution was extracted with 2 mL of chloroform
2 times and evaporated until dry with nitrogen gas. The
extract was reconstituted with 1 mL of mobile phase and
20 μL of the solution was injected into the HPLC system
to determine the amount of caffeine