2.3. Preparation of the sample solution
All samples, including soft drink, sugar-based and gelatin-based
confectionery, were obtained from a local market. Appropriate
amounts (0.3–2.5 g) of the samples were dissolved in 25 mL of
water. The carbonated drinks were degassed by ultrasonication
for 5 min. A warming process (50 C, 30 min) was used for the
complete dissolution of the sugar-based and gelatin-based confectionery.
Samples were diluted to 50 mL in a volumetric flask with
an acetate buffer solution (0.2 mol/L, pH 5.0). These solutions were
filtered through a folded Xinhua paper filter (No. 102), and the filtrate
was collected after discarding the first 15 mL.