Partition of native sodium, potassium, magnesium, calcium and radioisotopes of cesium, strontium and curopium was investigated in the aqueous liquid-liquid systems formed after agitation of fresh pasteurized skim bovine milk with 4% w/w water solution of pectin of various degree of esterification (60–93%). The partition of the ions in the membraneless dialysis was described by Donnan equilibria and ion-exchange in the macro- and microheterogenous systems and, within uncertainty of results, does not depend on the degree of esterification. Strong negative non-ideality of Sr and Eu in milk phase is attributed to binding with proteins, casein particles in particular, and complexation with low molecular ligands. Separation factor =D(Sr)/D(Ca) is 0.70±0.06, in favor of strontium concentration in pectin phase. While >96% of cesium is diffusible to pectin phase, only 43–56% (depending on physico-chemical model of dialysis) of strontium behaves in that way, and in original milk phase the percent of strontium cationic form may be as low as 13%.