氧化还原电位滴定法测定羟自由基

Redox Potentiometric Titration of Hydroxyl Free Radical

应用电位滴定法测定了羟自由基。加入过量的1.0×10^(-4)mol·L^(-1)硫酸亚铁溶液与羟自由基(·OH)反应,多余的亚铁离子用相同浓度的硫酸高铈溶液在经用硫酸酸化的溶液中进行返滴定。试验表明:羟自由基与亚铁离子之间的氧化还原反应在pH 4的微酸性溶液中进行,且此反应经8 min即告完成。据此,选用pH 4乙酸盐缓冲体系并在反应开始后10 min用硫酸高铈溶液进行滴定。应用此方法测定了样品中羟自由基含量,测得结果的相对标准偏差(n=10)为0.26%。此方法的检出限(3s/b)为3.1×10^(-7)mol·L^(-1)。

Potentio-titrimetry was applied to the determination of hydroxyl free radical. Excess of 1.0×10^-4mol·L^-1 ferrous sulfate solution was added to react with the hydroxyl free radical （·OH） and the un-reacted amount of ferrous sulfate was titrated potentiometrically with 1.0×10^-4mol·L^-1 ceric sulfate solution in the solution acidified with sulfuric acid. It was found that the optimum acidity of the solution for the redox reaction between ·OH and Fe^2＋ was pH 4, and that the time taken for completion of the reaction was 8 min. Based on these facts, acetate buffer was used and the back-titration with ceric sulfate solution was performed 10 min after the starting of reaction. In the determination of ·OH by the proposed method, value of RSD （n= 10） found was 0. 26%. Detection limit （3s/b） of the method was found to be 3.1×10^-7mol·^-1.