One of the important tasks of analytical chemistry at the present time is the development of reliable methods for environmental quality monitoring. To solve this problem, the determina-tion of trace amounts of various ions is widely used among the main analytical methods. On the basis of a copolymer of maleic anhydride with styrene, eight chelating sorbents containing the following fragments were synthesized: dithizone-1 (M1); 2-aminophenol-4,6-disulfonic acid (M2); o-acetylaminophenoxyacetic acid (M3); N,N′,N′-triphenylguanidine (M4); m-phenylenediamine (M5); 3-nitro-4-sulfoaminobenzene (M6); p-acetylamidobenzoic acid (M7); and norsulfazole (M8). The sorbents were synthesized using a known procedure, and their composition and structure were determined by IR spectroscopy. The physicochemical proper-ties of the synthesized sorbents were studied. To determine the ionization constants of the sorbents, the total static sorption capacity (P) with respect to K⁺ ions was investigated accord-ing to a known method. In determining P, the amount of consumed K⁺ ions was equivalent to the amount of carboxyl groups in the sorbent unit. The ionization constants of the obtained sorbents were determined by potentiometric titration. The conditions for the sorption of U(VI) and Th(IV) by the synthesized sorbents were studied. The developed methods were applied to the preconcentration of U(VI) and Th(IV) in various natural objects.