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4-(2-吡啶偶氮)间苯二酚(PAR)是常用的配位滴定指示剂和光度分析显色剂,能用于多种金属离子的光度测定.用PAR光度法测定Fe(Ⅱ),因PAR及其PAR与Fe(Ⅱ)的配合物在酸性介质中难溶于水,因而一般在选择性不够高的碱性介质中进行测定.迄今为止,PAR与Fe(Ⅱ)在酸性介质中的显色反应研究还未见报道,本法采用加入表面活性剂OP增溶,研究在酸性介质中PAR与Fe(Ⅱ)的显色反应.结果表明,在pH2.0～6.0的范围内,Fe(Ⅱ)与PAR形成稳定的1:2配合物,最大吸收波长为491nm和710nm,表观摩尔吸光系数ε_(710)为1.4×10~4L·mol~(-1)·cm~(-1),以710nm为测定波长,铁含量在0～45μg/25ml范围内服从比耳定律.方法选择性较高,用于测定茶叶和食品中微量铁,结果满意.
4- (2-pyridylazo) resorcinol (PAR) is a commonly used complexometric titration indicator and photometric analysis reagent, which can be used for photometric determination of various metal ions. PAR ), PAR and Fe (II) complexes are generally poorly selective in alkaline media because of their poor solubility in water in acidic media. To date, The study of chromogenic reaction in media has not been reported yet and the color reaction of PAR and Fe (Ⅱ) in acid medium was studied by adding surfactant OP solubilization.The results showed that under the condition of pH2.0 ~ 6.0 , The stable 1: 2 complex formed between Fe (Ⅱ) and PAR, the maximum absorption wavelength is 491nm and 710nm, and the apparent molar absorptivity ε 710 is 1.4 × 10 4 L · mol -1 cm -1. (-1), with the determination wavelength of 710nm, Beer’s law is obeyed in the range of 0 ~ 45μg / 25ml.The method has high selectivity and is suitable for the determination of trace iron in tea and food with satisfactory results.