Determination of vitamin C in fruits by fading spectrophotometry with iodine starch system

Iodine and starch could found a blue complex which had maximum absorption wavelength of 590 nm. When Vc was added into the iodide starch system in a acidic condition about pH 4.0, the iodide were reduced to Iodide ions, and the blue complex’s absorbance would went down. The reduction of absorbance (ΔA) had good linear relationship with the contents of Vc from 1 μg/mL to 7 μg/mL. The linear regression equation is ΔA=0.0036C Vc +0.0114 and R 2 =0.9999, the recovery of the method were 99.8%～103.2%, and relatively standard deviation were 1.5%.