在稀硫酸溶液中,铁(Ⅲ)与碘化钾反应生成游离碘(以络阴离子I-3状态存在).所释出的I-3与罗丹明6G反应生成离子缔合络合物,导致罗丹明6G的荧光猝灭.在激发波长483 nm及发射波长551 nm处测定空白试液及含铁试样溶液的荧光强度F0及Fs并算得荧光猝灭强度ΔF.试验结果表明:铁(Ⅲ)的质量浓度在0.01~0.40 mg·L-1范围内与其相应的荧光猝灭值ΔF之间呈线性关系,并测得其检出限(S/N=3)为0.005 mg·L-1.应用此方法测定了3种农产品试样中的含铁量,并以此试样为基体加入铁(Ⅲ)标准溶液测定了方法的回收率在95.7%~99.3%之间.

In a dilute sulfuric acid solution,ferric iron reacted with potassium iodide to give free iodine (in form of its anionic complex I-3),which in turn reacted with rhodamine 6G to form an ionic association complex,leading to the quenching of fluorescence of rhodamine 6G. Values of intensity of fluorescence quenching,ΔF (ΔF=F0-Fs) were measured at λex 483 nm and λem 551 nm. It was found that linear relationship between the magnitude of values of ΔF and the concentration of Fe(Ⅲ) ion was kept in the range of 0.01-0.40 mg·L-1,with its detection limit (S/N=3) of 0.005 mg·L-1. Base on these facts,a method of fluorospectrophotometric determination of iron in agricultural products was proposed. The proposed method was used in the analysis of 3 kinds of agricultural products,on the base of which standard iron solutions were added to test for recovery of the method. Values of recovery found were in the range from 95.7%-99.3%.