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在p H值为5左右的HAc-NH4Ac缓冲溶液中铁(Ⅱ)与2,2’—联吡啶生成有色络阳离子,与强酸性阳离子交换树脂进行交换吸附,即可进行树脂相分光光度法测定微量Fe(Ⅱ)。最大吸收波长λmax=522 nm,表观摩尔吸光系数为9.8×104L·mol-1·cm-1,比水相分光光度法测定Fe(Ⅱ)的摩尔吸光系数高出近12倍。铁(Ⅱ)的含量在0.2~20mg·L-1范围内服从Beer定律。测定了黑豆、红豆、荞麦和莜麦样品中的微量铁,相对标准偏差为1.9%~3.5%,回收率在97.8%~103%之间,结果满意。
In the HAc-NH4Ac buffer solution with p H of about 5, iron (Ⅱ) and 2,2’-bipyridyl generate colored colorant, exchanged with strongly acidic cation exchange resin, then the resin phase spectrophotometric method can be used for the determination of trace Fe (Ⅱ). The maximum absorption wavelength is λmax = 522 nm, the apparent molar absorptivity is 9.8 × 104 L · mol-1 · cm-1, which is almost 12 times higher than the molar extinction coefficient of Fe (Ⅱ) measured by aqueous spectrophotometry. Iron (Ⅱ) content in the range of 0.2 ~ 20mg · L-1 Beer’s law. The trace iron in black bean, red bean, buckwheat and oat was determined. The relative standard deviations were 1.9% ~ 3.5%, and the recoveries were between 97.8% ~ 103%. The results were satisfactory.