Abstract
When retinoic acid in chloroform solution was reacted with different concentration of sulfuric acid (75-95%), the sulfuric acid layer showed two maximal peaks of absorption at 440mμ and 540mμ, respectively. The absorbance at 440mμ increased and the peak was shifted to 450mμ with dilution of sulfuric acid. When 74% sulfuric acid was used, the maximal absorbance at 450mμ was obtained, while the peak at 540mμ disappeared. The yellow color of the 74% sulfuric acid layer was stable and intensity of the color was completely proportional to the concentration of retinoic acid. From the results, it was concluded that retinoic acid could be determined quantitatively by colorimetric assay of 74% sulfuric acid layer at 450mμ.
