Interpolimer maleic anhydride-styrene has been modified in the presence o-aminofenol and formaldehyde and a new polymeric sorbent with the spatial structure has been obtained. Statistical sorptive capacity of tinning sorbent on the K+ ion has been considered and potentiometric method determined constants to ionizing ionogenic groups in the section of sorbent. Optimum conditions for sorptions of the ions Cu(II): dependency to sorption from a time, ion power and mass of sorbent studied. Also, influence of ambience under occlusion and complexing and influence of different mineral acids on about-cession an desorption retrased.