A novel highly selective sensitive for decreasing the detection limit for a Cu(II), Zn(II) and Co(II) have been fabricated fromion-selective electrode (ISE).The ISE is designed using acetaldehydethiosemicarbazone complex as ion-exchanger in carbon pastedissolved in tricresyl phosphate (TCP) as pasting liquid were prepared.This work describes the attempts to develop the electrodes, measurements of their characteristics and determination in real samples.The developed sensors exhibit good linear response of Nernstian slopes of 29.5±1, 28.5±1and 29.0±1 mV per decade over the concentration range of 5.0×10−8-2.0×10−3, 6.3×10−8- 7.9×10−3 and 3.3×10−8-8.0×10−3 M and a detection limit of 0.26, 0.5and 0.3nM for Cu(II), Zn(II) and Co(II) respectively. The sensors have a relatively fast response time of less than 10 s and the selectivity coefficients of the proposed electrodes revealed very good selectivity with respect to alkali, alkaline earth and some transition metal ions and could be used in pH range of 3.5-8.0. As a result the proposed electrodes were successfully applied to Cu(II), Zn(II) and Co(II) ions determination in mixture solutions and wastewater samples and as an indicator electrodes for potentiometric titration of ions with EDTA. The isolated complexes, HATS were synthesized by the anodic dissolution of metal in an anhydrous acetone solution of the ligands where HATS is acetaldehydethiosemicarbazone ligand and ac = acetone. Elemental analysis, magnetic susceptibility measurements, molar conductance, thermal analysis and spectroscopic techniques has been used for characterization and elucidation of the isolated complexes.