Dear Hadi,

I am using below mentioned method which is exactly what you need but if you need another method i can forward you lot of methods available.

Simultaneous determination of nutritionally important minerals in food samples is in great demand. Ion chromatography coupled with UV-vis detection is shown to be an appropriate technique for this objective. The method is based on the formation of mineral complexes by pyridine-2,6-dicarboxylic acid in the mobile phase. The complexes are then postcolumn derivatized with 4-(2-pyridylazo)resorcinol (PAR), resulting in mineral-PAR complexes that are detected by UV-vis absorption at 500 nm. This facilitates the simultaneous separation and quantification of minerals in one chromatographic run. Within 16 min, Cu, Ni, Zn, Co, Mn, and Fe are analyzed. When a 50 µl injection volume is used, the average detection limit is 5 ppb in the injection liquid. The detection limit makes it a superior alternative to AAS and, in several applications, also an alternative to ICP-MS techniques. Different sample treatments were evaluated. The concentration of acid in the treated sample varied with the sample treatment, which may cause a limitation for the injection volume. A crucial prerequisite to achieve the reported detection limits and to obtain reliable results is to completely exclude all contamination from instruments and materials.

Reference:

Simultaneous and sensitive analysis of Cu, Ni, Zn, Co, Mn, and Fe in food and biological samples by ion chromatography.

By Mattias M Fredrikson, Nils-Gunnar NG Carlsson, Annette A Almgren, Ann-Sofie AS Sandberg

Journal of Agricultural and Food Chemistry 2002-01-02

PMID 11754542

Complete method is attached with this please check and inform me if you need further information please ask it is also interesting topic for me I think it will help you.

Regards

Amir

@ Michael: can you explain more on ICP?

@Amir, Thanks for your reference.