Study on Quantitative Determination of Salicylic Acid in Aspirin with Spectrophotometry

To discuss the rapid and accurate method for determination of salicylic acid in aspirin based on spectrophotometer technology.A violet complex was obtained when Fe3+ and salicylic acid were mixed together in proper conditions.By measuring the absorbance of aspirin solution in which salicylic acid as the impurity,and FeCl3 added as a colour developing agent,the quantity of salicylic acid in aspirin was determined.The conditions affecting the formation and stability of the complex were studied,such as pH,temperature,reaction time,the consumption of Fe3+.Under perfect conditions,the standard curve was achieved.The final results showed that in buffer solution of CH3COOH-CH3COONa,in which the pH value was 3,Fe3+ and salicylic acid produce a considerably stable complex by the ratio 1:1,and the reaction favorably finished within 10 minutes at room temperature.The wavelength of maximum absorption of the complex was 512 nm.The relative error of this determination was about 2.5%.