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在pH 10.0的NH3-NH4Cl缓冲溶液中,微量Fe(Ⅲ)对罗丹明B的荧光强度具有明显的猝灭作用.实验研究了该猝灭反应并讨论了将其应用于铁(Ⅲ)分析的最佳条件.实验表明,于25 mL比色管中,分别依次加入3.00 mL罗丹明B溶液、一定量的Fe(Ⅲ)标准溶液、2.00 mL pH 10.0的NH3-NH4Cl缓冲溶液,用水稀释至刻度,摇匀,用1 cm四面透光的石英比色皿进行测定,体系的最大发射波长λem=580 nm,最大激发波长λex=550 nm.Fe(Ⅲ)的质量浓度在0.004~0.028 μg/mL范围内与其对应的荧光猝灭值ΔF呈良好的线性关系,相关系数为0.987 9,方法的检出限为0.003 8 μg/mL.将实验体系应用于不同环境水样(矿泉水、山泉水、自来水)中Fe(Ⅲ)的测定,测得结果与原子吸收光谱法(国家水质标准方法GB 11911-1989)基本一致,相对标准偏差(RSD,n=6)为3.5%~7.5%,回收率在99%~106%之间.

Micro Fe(Ⅲ) showed obvious quenching effect on the fluorescence intensity of rhodamine B in NH3-NH4Cl buffer solution at Ph 10.0.This quenching reaction was investigated and the optimal conditions for its application in Fe(III) analysis were discussed.In 25 Ml colorimetric tube, 3.00 Ml of rhodamine B solution, certain volume of Fe (III) standard solution and 2.00 Ml of NH3-NH4Cl buffer solution at Ph 10.0 were added.The solution was diluted to the mark with water.After shaking up, it was determined in 1 cm quartz cuvette which was pervious to light all around.The maximum emission wavelength and maximum excitation wavelength of system was λem=580 nm and λex=550 nm, respectively.The fluorescence quenching value (ΔF) showed linear relationship to the mass concentration of Fe(III) in range of 0.004-0.028 μg/Ml with correlation coefficient of 0.987 9.The detection limit of method was 0.003 8 μg/Ml.The proposed method was applied for the determination of Fe (III) in various environmental water samples (mineral water, spring water and tap water).The results were consistent with those obtained by atomic absorption spectrometry (GB 11911-1989 of national standard analysis method for water quality).The relative standard deviations (RSD, n=6) were between 3.5% and 7.5%.The recoveries were between 99% and 106%.