The high-performance size-exclusion chromatography (HPSEC) and radiochromatography (HPSERC) was used for the identification of radiocesium and radiostrontium interaction with humic acid. It was found that the behavior of humic acid on size-exclusion chromatography is sensitive to the salt concentration and pH of the mobile phase. At lower ionic strength and in acidic region ofpH, the Aldrich humic acid exhibited three main fraction within the ranges >760 kDa, 25-100 kDa and <5 kDa. Radiocesium was found in the low-molecular fractions (<1 kDa) of humic acids but radiostrontium interacts preferably with the fractions of humic acid of molecular weight within the range 2-5 kDa.

Aqueous two-phase systems allow partition of metal ions in nondenaturing conditions. From the fresh skim bovine milk spiked with 212pb and agitated with 4% water solution of apple pectin (degree of esterification ~0%), less than 2.3% is recovered to the pectin phase and in the case of pasteurized milk less than 3.0%. Complexation with chelate forming agents was studied. Aminoacids as glycine, alanine and histidine do not exert influence on the yield, but the recovery in the pectin phase was 22% for cysteine, and 80% in the case of Edtacal TM (calcium salt of ethylenediaminetetraacetic acid). The retention of lead in milk phase is extraordinarily high as compared to strontium and corresponds to the behavior of trivalent ions.

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Speciation of fission products (9~ 99Tc, 137Cs and 152Eu) in raw cow milk was studied using the high-performance size exclusion radiochromatography (HP-SERC) by Biosep-SEC-S | column (Phenomenex, USA). The separation fraction were identified by a UV detector (280 nm) and a scintillation radiodetector. The mobile phase was Jenness-Koops buffer that simulated milk serum. Radiocesium was present only in non-protein fractions. The non-protein fractions complexed 17% of technetium and 57% of strontium. About 32% of strontium and 24% of europium were bound on the high molecular weight proteins (micellar casein). Low molecular weight proteins bound about 11% of strontium and 76% of europium. Non-size effects play a dominant role at HPSERC speciation of technetium, 83% of which follow the lightest fractions of milk.

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