For analysis in cuvettes a volume of 0.5 mL of appropriately
diluted samples, blanks or standards was placed into test tube followed by addition of 0.5 mL of Folin-Ciocalteu
Phenol Reagent and 7.5 mL of deionised water. After 10 min, 0.5 mL of sodium carbonate (20%, w/v) was added.
Samples were vortexed and incubated for 20 min at ambient temperature in the dark for 20 min.