利用Fe(III)和 2 (5′ 溴 2′ 吡啶偶氮 ) 5 二乙基氨基苯酚反应形成配位化合物为基础 ,研究一种灵敏的计时吸附电位法测定KH2 PO4 中超痕量Fe(III)含量。讨论了KH2 PO4 对Fe(III)与 2 (5′ 溴 2′ 吡啶偶氮 ) 5 二乙基氨基苯酚反应的影响。在电化学检测前利用PbS生成Fe2 S3共沉淀 ,将Fe(III)从KH2 PO4 溶液中分离出来。该方法用于测定了KH2 PO4 晶体和饱和溶液中超痕量Fe(III)含量 ,获得满意结果 Based on the coordination reaction between Fe (III) and 2 (5’-bromo 2’-pyridylazo) 5 diethylaminophenol, a sensitive time-dependent sorption potential method was developed for the determination of ultra trace amounts of Fe (III) content. The effect of KH2 PO4 on the reaction of Fe (III) with 2 (5 ’bromopyridine azo) 5 diethylaminophenol was discussed. Precipitation of Fe2 S3 by PbS before electrochemical detection was performed to separate Fe (III) from KH2 PO4 solution. This method was used to determine the amount of ultra-trace Fe (III) in KH2PO4 crystals and saturated solutions, and satisfactory results were obtained