Determination of Oxalic Acid in Compound Vitamin(3)for Injection by Spectrophotometry

Trace oxalic acid in compound vitamin(3) for injection was determined by spectrophotometriy.In buffer solution of potassium chloride-hydrochloric acid,Fe3+ and oxalic acid complex can make Fe3+ with sulfosalicylic acid violet complex of lighter color,the absorbance after color reaction was determined.Chromogenic reaction time and amount of color reagent was optimized in the tests.The results showed,the maximum absorption wavelength of color solution was 503nm.There was a good linear relationship between absorption and concentration of oxalic acid in the range of 0.006—0.036mg/mL.The regression equation was y=-17.552x+1.0283,r=0.9991.Sample recovery rate was 97.6%.The method can accurately check the compound vitamin(3) for injection of trace oxalic acid.