The Determination of Analginum by the Iron(III)-sulfosalicylic Acid Spectrophotometric Method

The content of analginum in preparations was determined by the iron(Ⅲ)sulfosalicylic acid spectrophotometric method with the iron(Ⅲ) as the oxidizer of analginum and sulfosalicylic acid as the color metric reagent for iron(Ⅲ). As shown in the experiment, when iron(Ⅲ) met sulfosalicylic acid, two kinds of complexes were formed with the ratio of 1∶1 and 1∶2, and the maximum absorption wavelengths of 500 nm and 470 nm at the pH 24 and pH 54, respectively. The addition of analginum made the iron(Ⅲ)sulfosalicylic acid complexes declored, so two new iron(Ⅲ)sulfosalicylic acid system methods were obtained for the determination of analginum in preparations with the regressive equations of A1=0013 00ρ-0031 and A2=0022 05ρ-0015, and the coefficient γ of 0999 9 and 0999 8. Beer's law was obeyed at the analginum concentrations of 0～40 mg/L and 0～56 mg/L, respectively. The proposed method has been applied to the determination of analginum in preparations with satisfactory results, which are in agreement with those obtained by the ultraviolet spectrophotometric method.