浊点萃取—光度法测定加碘食盐中碘的含量

Determination of Iodine in Iodized Salt by Cloud Point Extraction-Spectrophotometry

在酸性介质中,碘酸钾(KIO3)与过量碘离子(I-)反应生成定量单质碘(I2),I-3与阳离子染料3,6-双(二甲基氨基)吖啶在弱酸条件下形成疏水性离子缔合物,进行浊点萃取,光度法测定。研究了溶液的酸度、试剂用量、平衡时间、平衡温度、离子强度对浊点萃取效果的影响,并得到最佳实验条件:10%的Triton X-114用量1.0 m L、平衡温度60℃、平衡时间20 min,将表面活性剂富集相用乙醇分散稀释,应用紫外—可见分光光度计进行450 nm波长处测定。在最佳条件下,测定的线性范围为5.0μg/m L^200μg/m L,方法的检出限为0.2μg/m L,相对标准偏差(RSD)为1.2%~3.0%。

In the acidic medium, potassium iodate （KIO3 ） reacts with excess iodide ion （I-） to produce quantitative elemental iodine（ 12 ）. 13- and cationic dye 3,6 -bis（dimethylamino） acridine in weak acid condition. The formation of hydrophobic ion association was extracted by cloud point and determined by photometric method. The effect of acidity, reagent dosage, equilibrium time, equilibrium temperature and ionic strength on the extraction of cloud point was studied. The optimum experimental condition was obtained that 10% TritonX - 114 with dosage 1.0 mL, equilib- rium temperature 60 ℃, equilibrium time 20 min, the surfactant - enriched phase was diluted with ethanol and measured at 450 nm using an ultraviolet - visible spectrophotometer. Under the opti- mum condition, the linear range was 5.0 μg/mL ~ 200 μg/mL. The detection limit was 0.2 μg/mL and the relative standard deviation（RSD） was 1.2% -3.0%.