Determination of Micro Ascorbic Acid by Inhibition Kinetic Spectrophotometry —NO_~2-—KBrO_3—MA Systems

A new inhibition kinetic spectrophotometric method for the determination of micro ascorbic acid is studied. The method is based on the inhibition ofascorbic acid on the nitrite catalyzed oxidation of malachite green by potassium bromate in phosphoric acid medium. The absorbance is measured at 620 nm. The linear range of determination is 0.20～1.40 μg/mL. The detection limit is 2.5×10-7 g/mL. The relative standard deviation was 3.2%(n=10,10.0 μg/25mL, ascorbic acid). The method is applied to the determination of ascorbic acid in vitamin C tablet with satisfactory results.