Quantitative analysis by using calibration curve
1. Prepare the gallic acid at the concentration of 200 ppm by using distilled water as
a solvent.
2. Dilute gallic acid solution to various concentrations including 25, 50, 75, 100 and
150 ppm by using distilled water as a solvent.
3. Mix each concentration of gallic acid standard (0.5 ml) with 0.5 Folin–Ciocalteu
reagent, 0.5 ml distilled water and 2.5 ml of 2% sodium carbonate.
4. Incubate 20 minutes at ambient temperature under dark condition.
4. Measure the absorbance of the resulting mixture at 725 nm by spectrophotometer