SPECTROPHOTOMETRIC DETERMINATION OF GIBBERELLIN BY MOLYBDEMUM BLUE METHOD

The method developed in this communication consists of the reduction of 12-molybdophosphoric acid to molybdenum blue by gibberellin either in sulfuric acid or in perchloric acid after heating for forty minutes in a boiling water bath.The optimum acidities should be 1.25～1.40 N in sulfuric acid or 1.68～1.92 N in perchloric acid. The absorption maximum, molar absorptivity and sensitivity of the color reaction were shown to be 710nm, 4.40×10³ 1 mole^-1 cm^-1, and 0.4μg/ml, respectively. The working wavelength is 650 nm. The color intensity is stable over a 160-hour period and is found to obey Beer's law within the concentration range of 0～1 mg and 1～5 mg per 25 ml.The proposed method is simple and reliable. It has been applied to the determination of gibberellin in pure gibberellin crystalline powder and its various pharmaceutical preparations.