Dual-wavelength spectrophotometric determination of zinc with Zn~(2+)-phen-bright yellow association system

A new method for the determination of micro zinc by double-wavelength spectrophotometry using 492 nm as the detection wavelength and 379 nm as the reference wavelength was developed.In NaAc-HAc buffer solution at pH 5.7,Zn2+ reacts with phen and bright yellow(BY) to form a stable ion-association complex [Zn(phen)3]BY,which leads to the fading of BY.As a result,there were a positive Absorption peak at 492 nm and a negative Absorption peak at 379 nm.The apparent molar Absorption coefficient was 3.01×104 L·mol-1·cm-1.The linear range of the determination was 0～1.5 μg/mL,and the limit of detection for zinc was 18.5 μg/L.The method has been applied to the determination of zinc in zinc-fortified nutritious salt and health balance salt.RSDs of 5 determinations were 0.69%～0.87%.Recoveries were 98.4%～99.3%.