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The influence of kinetic properties of several extraction systems on the separation of some elements by countercurrent chromatography (CCC) has been studied. The chromatographic behaviour of Eu(III), Fe(III), Ta(V), Nb(V), Hf(IV), Zr(IV) has been investigated in two kinetically different extraction systems on the basis of di-2-ethylhexylphosphoric acid (D2EHPA) and tetraphenylmethylenediphosphine dioxide (DTPMDP). It has been shown that the values of mass transfer coefficients determine the type of elution (isocratic or step), which is necessary for the element separation. The data on batch extraction (mass transfer coefficients and partition coefficients) and parameters of chromatographic peaks (half-widths) can be interrelated by the expression proposed.

In countercurrent chromatography (CCC) both stationary and mobile liquids undergo intense mixing in the variable force field of a coil planet centrifuge and the separation process, like the separation in conventional solvent extraction column, is influenced by longitudinal mixing in the phases and mass transfer between them. This paper describes how the residence time distribution (or the elution profile) of a solute in CCC devices and the interpretation of experimental peaks, can be described by a recently developed cell model of longitudinal mixing. The model considers a CCC column as a cascade of perfectly mixed equal-size cells, the number of which is determined by the rates of longitudinal mixing in the stationary and mobile phases. Experiments were carried out to demonstrate the validation of the model and the possibility of predicting the partitioning behaviour of the solutes. The methods for estimating model parameters are discussed. Longitudinal mixing rates in stationary and mobile phases have been experimentally determined and experimental elution profiles are compared with simulated peaks. It is shown that using the cell model the peak shape for a solute with a given distribution constant can be predicted from experimental data on other solutes.

Partition countercurrent chromatography can be used for the concentration and separation of elements of similar properties in aqueous solution — extradant systems. The angle of wetting of the column wall with the components of a two-phase liquid system has a considerable effect on the retention of the stationary phase. The method was used for the separation of orthophosphate and pyrophosphate (extradant — solution of dinonyltin dichloride in methylisobutylketone), cesium and strontium (solution of cobalt dicarbollide in nitrobenzene) and rare earth elements (di-2-ethyhexylphosphoric acid in decane).

Extraction—chromatographic separation of ortho- and pyrophosphate anions on an inert support modified with an organotin extractant was studied and used for their subsequent determination in a flow-injection system. The proposed FIA manifold includes an extraction—chromatographic mini-column, on which the phosphate anions are separated and preconcentrated, and a post-column spectrophotometric detector. For the determination of orthophosphate, the absorbance of the reduced 12-molybdophosphoric acid is monitored at 660 nm. The sum of ortho- and pyrophosphate can be determined after preliminary hydrolysis of pyrophosphate to orthophosphate in neutral solution at 50° by use of inorganic pyrophosphatase. For a sample volume of 6 ml, the calibration graph is linear within a range of 5.0–100.0 ng/ml P. The limit of detection is 0.3 ng/ml P. The recovery of the ions to be determined is not less than 96%, the relative error is not worse than 4%. The proposed method was used for the analysis of river water samples.