The usage of diglycylglycine (GGG) was proposed to improve the separation of the complexes of heavy metal ions with EDTA by capillary zone electrophoresis. The tripeptide can interact with the complexes in capillary and thereby acts as a complex selector. The influence of GGG on the electrophoretic behavior of ten metal complexes (Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Pb(II) and Bi(III)) was studied in an acidic media using a negative polarity voltage supply. Three modes were proposed for the implementation of the in-capillary complexation. An addition of the reagent to the phosphate buffer solution changes the migration order of the complexes thus enabling separation of Cr(III) from Zn(II) and Ni(II) and Co(II) from Cd(II) and Mn(II). It is possible to determine Fe(III) and Bi(III) complexes selectively in presence of the other heavy metal ions. An injection of separate zones of EDTA, metal ions and GGG doesn’t provide good separation. A consecutive injection of Me-EDTA and GGG zones leads to Cu(II) and Pb(II) separation. So, it is possible to determine four metal ions (Cu(II), Pb(II), Fe(III) and Bi(III)) simultaneously at 260 nm. Calibration graphs plotted in optimal conditions show linearity within the concentration range from 5·10 -6 to 5·10 -3 mol/dm 3. Limits of detection were calculated to be from 0.05 mg/dm 3 for Pb(II) ions to 0.72 mg/dm 3 for Bi(III). The proposed technique was applied for the determination of copper, lead, iron and bismuth in some natural and industrial samples.