The non-carbonated samples were analysed without any
special treatment. The carbonated samples were analysed
by stirring for 30 min to obtain a degassed, ready-to-drink
beverage. The powdered samples were prepared following
the instructions on the package. An aliquot of each sample
was mixed with an equal volume of acetonitrile and then
centrifuged at 2000 rpm for 15 min. A 1.0mL aliquot of
the supernatant was mixed with an equal volume of a
0.05 mg/mL ferric chloride solution. The resulting mixture
was then filtered through a 0.20 mm pore diameter
membrane before injection. All samples were processed
three times and each of the replicates was injected two
times.