苦安酸偶氮变色酸褪色光度法测定硅铁中的铁含量

DETERMINATION OF IRON IN SILICON IRON BY PICRAMINE CA-DISCOLORING SPECTROPHOTOMETRY

基于pH7.8的氨水-氯化铵介质中显色剂苦安酸偶氮变色酸与铁的褪色反应,建立了测定硅铁中铁含量的褪色光度分析方法。讨论了吸收光谱、酸度、显色剂用量、干扰离子等因素的影响,确定了反应的最佳条件。铁量在2～40μg/(25mL)范围内符合比耳定律,表观摩尔吸光系数为3.27×104L.mol-1.cm-1。用该方法对硅铁标准样品中的铁进行测定,测定结果与标准值的相对误差低于0.3%,RSD为1.4%～2.1%(n=6)。

A sensitive spectrophotometric method was developed to determine iron in silicon iron based on the discoloring reaction of iron picramine CA system in NH3 · H2O - NH4 Cl medium （ pH 7.8 ）. The influence factors such as absorption spectra, acidity, concentration of reagent, coexisting ions were discussed. The optimal reaction conditions were established. Beer＇ s law was obeyed in the range of 2 -40 μg/（25 mL） for iron with apparent molar absorptivity of 3.27 × 10^4 L · mol^-1 . cm^-1. The method was applied to determining iron in silicon iron standard materials. The relative error was less than 0.3% , RSD was 1.4 % - 2.1% （n =5）.