Determination of Trace Amount of Iron in Agricultural Products by the Quenching of Fluorescence of Rhodamine 6G

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%.