磺基水杨酸-铁(Ⅲ)显色体系间接测定左旋多巴的研究

Study on the Indirectly Determination of Levodopa by Sulfosalicylic Acid-iron(Ⅲ) Color Reaction System

磺基水杨酸与Fe（Ⅲ）在pH=2.00~3.00的溶液中形成紫红色磺基水杨酸合铁（Ⅲ）配离子,左旋多巴的还原性,可将Fe（Ⅲ）定量还原为Fe（Ⅱ）,使Fe（Ⅲ）-磺基水杨酸体系的颜色褪去,其吸光度降低值与左旋多巴含量在一定范围内呈良好的线性关系,据此提出了基于Fe（Ⅲ）-磺基水杨酸显色体系间接分光光度法测定左旋多巴含量的新方法。对实验条件进行了研究和选择。方法线性范围为4.0×10-7~2.0×10-5mol/L,检出限为3.1×10-7mol/L,回收率为98.0%~101.0%。该方法简单、快速、灵敏,用于片剂中左旋多巴的测定,结果满意。

The sulfosalicylic acid and Fe（Ⅲ） could form a purple-red complex in pH=2.00～3.00 solution,the reducing nature of levodopa could reduce Fe（Ⅲ） to Fe（Ⅱ）,thus the absorbance of the Fe（Ⅲ）-sulfosalicylic system decreased.The absorbance reduction of Fe（Ⅲ）-sulfosalicylic system and the contents of levodopa appeared linear relationships.A new method for the indirectly determination of levodopa has been developed based on the characteristic.Different conditions affecting the absorbance were studied and optimized.Under the optimum experimental conditions,the linear range was 4.0×10-7～2.0×10-5mol/L,the detection limit for levodopa was 3.1×10-7mol/L and the recoveries were 98.0%-101.0%.The method was simple,accurate and sensitive,and has been used to determine the levodopa in tablets with satisfactory results.