where DF is the dilution factor of measured solution from stock standard solution, A the absorbance of measured solution (A < 1) with reference to water, the expression A1% 1 cm represents the specific absorbance of an 1% (10 g L−1) aqueous solution of the colorant at the prescribed wavelength using a path length of 1 cm at 20 ± 1 ◦C, and C is the concentration of stock solution expressed as the mg of the unpurified colorant in 100 mL distilled deionized water. The A1% 1 cm value for each compound is presented in Table 2