Fluorospectrophotometric Determination of Traces of Iron in Milk Powder and Water Sample by Quenching of Fluorescence of Tyrosine

In an acetate-borate-phosphate buffer medium of pH 4.46,a complex was formed by the reaction between Fe(Ⅲ) and tyrosine,leading to quenching of inherent fluorescence of tyrosine.Linear relationship between the magnitude of decrease in fluorescence intensity (ΔF) and concentration of Fe(Ⅲ) was obtained in the range of 1.6×10-8-3.2×10-5mol·L-1 when measured at the wavelengths of 277 nm (λex) and 306 nm (λem).Contents of iron in a water sample and a sample of milk powder were determined by the proposed method,giving results in consistency with those obtained by the o-phenanthroline photometric method.Using these samples as matrixes,test for recovery was made by standard addition method,values of recovery obtained were in the range of 98.2%-99.9%,with values of RSD′s (n=5) less than 3%.Detection limit (3sb/k) of the method was found to be 1.2×10-8mol·L-1.