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A complex procedure has been developed for evaluating the degree of soil contamination. Rotating coiled columns (RCCs) were used for both the fractionation of soil samples by their grain-size composition and the sequential extraction of heavy-metal species from silty, dusty, and sandy fractions. During the extraction of heavy-metal species, the soil fraction to be analyzed was retained in the column as a stationary phase, while aqueous solutions of extracting agents (mineral salts, acids, and complexing compounds) were sequentially pumped through the heterogeneous sample. The sequential extraction of element species from various soil fractions was carried out in the dynamic mode favorable to more complete extraction of metals. The use of RCCs allows the extraction of various heavy-metal species from soils to be performed in accordance with their grain-size composition. The process of the extraction of metal species can be automated, and in this case the losses of sample components are reduced to a minimum.

The effect of hydrodynamic parameters and the specific features of instrument design on the efficiency of substance separation in countercurrent liquid chromatography (CCC) was studied using a constant retention factor of the stationary phase in the column. The study was conducted with the separation of benzyl alcohol and p-cresol in a two-phase liquid system heptane–ethyl acetate–methanol–water (1.4 : 0.6 : 1 : 1) in as an example. It was shown that the peak resolution is improved with an increase in the rotational speed of the column and a decrease in the flow rate of the mobile phase. The best peak separation was attained using columns for which the ratio of the column rotation radius to the radius of column revolution was 0.615. It was shown that countercurrent chromatography allows the separation of substances with low partition constants (K < 1) in dilute solutions. The volume of the test sample may be up to 15% of the total volume of the chromatography column.

Conditions of the liquid–liquid and solid-phase extraction of metal chelates are compared. The analogy and differences in the behavior of chelates and the effect of stability and partition constants on the completeness of the extraction of metals are discussed.

The potentialities and advantages of using rotating coiled columns for the field-flow fractionation of solid microparticles in the transverse field of centrifugal forces were considered. Some peculiarities of the particle behavior in a rotating coiled column were studied using the retention and separation of model latex and silica gel particles as an example. The effects of the column type, its rotation speed, the flow rate of the carrier liquid, and the inner diameter of the column were studied. It was shown that the weight of solid particles in the sample can be 20 μg and more. On the basis of the revealed regularities, the conditions for separating particles of irregular shapes (quartz sand 1–20 μm) were found.

The effects of physicochemical properties of two-phase liquid systems (interfacial tension and differences in density and viscosity) on the retention of the stationary phase in the column were examined. These effects mainly determine the separation parameters of compounds. Extractant/decane–aqueous phase systems were used; their physicochemical properties changed both as a result of adding an extractant (di-(2-ethylhexyl) phosphoric acid, trioctylamine, or tributyl phosphate) to the organic solvent and because of a change in the composition of the aqueous phase. Aqueous ammonium sulfate of varying concentration was used as a mobile phase. It was shown that interfacial tension substantially affects the behavior of the systems under consideration. An increase in the ammonium sulfate concentration only slightly affects the retention factor of the stationary phase in the column. With a proper choice of the stationary phase, countercurrent chromatography can be used for the extraction of components from salt solutions of various concentrations.

The potentialities of rotating coiled columns in countercurrent chromatography (CCC) and centrifugal field-flow fractionation (CFFF) are demonstrated. A rotating coiled column is a fluoroplastic or steel coil wound around a rigid cylindrical drum, which revolves about its axis and, at the same time, revolves around the central axis of the device called planet centrifuge. The stationary (liquid, solid, or heterogeneous) phase is retained in the column because of the centrifugal force field, and the mobile liquid phase is continuously pumped through the column. The methods for recovery, separation, and preconcentration of various trace elements in geological samples and high-purity substances with the use of two-phase liquid systems (CCC) are developed. Procedures are proposed for the continuous sequential extraction of various element species from soil and for the recovery of polycyclic aromatic hydrocarbons from sewage sludge with the use of natural suspensions or solid particulates as stationary phases. It is also shown that rotating coiled columns can be used in a new field, microparticle fractionation by CFFF.

A mathematical model was developed which describes the behavior of various liquid systems in a rotating coiled column used in countercurrent chromatography. The conditions of retaining the liquid stationary phase were described in detail for hydrophilic (slowly settling) systems. Various forces that act on liquids in the column were considered. Equations were derived for the steady-state retention process. Mathematical expressions were obtained which make it possible to estimate the stationary-phase volume retained in a column with consideration for the physicochemical properties of the liquid system in use, the speed of column rotation, and the main design parameters of the planet centrifuge. This volume directly affects the column capacity and separation efficiency, and it is crucial for choosing liquid systems and experimental conditions.

A method has been developed for the separation of the entire group of rare-earth elements from high-purity calcium chloride by countercurrent chromatography, and subsequent determination of the elements by ICP-MS. A solution of diphenyl[dibutylcarbamoylmethyl]phosphine oxide in chloroform (0.5 mol L(-1)) has been chosen as reagent for the extraction and preconcentration of trace rare-earth elements from aqueous 5% CaCl2 solution, 3 mol L(-1) in HNO3 and 0.1 mol L(-1) in HClO4. The analytes are back-extracted into a small volume of water and the aqueous eluate is subjected to ICP-MS measurements. The performance characteristics of the procedure developed have been checked by use of the standard addition technique and a real CaCl2 sample (Merck product) has been analyzed. The results obtained demonstrate the applicability of countercurrent chromatography to the determination of ultratrace elements.

A procedure was proposed for the preconcentration of Sr, Cs, Pb, Co, Bi, and Ce beta radionuclides by solid-phase extraction as ion-pair complexes in the system dicyclohexyl-18-crown-6–sodium dodecyl sulfonate.

An improved device was proposed for the fractionation and preconcentration of particles and macromolecules. The device provides new means for the separation of water components. In the proposed method, a tangential flow of the test solution is passed through a series of successive membranes with decreasing pore size. The method was applied to the fractionation of low-mineralized water (Ty va Arzhaanes) with low concentrations of trace components.

Solid-phase extraction (SPE) of Eu(III) and Am(III) in systems containing a chelating agent and a neutral electron-donor compound was studied. In the systems 1-phenyl-3-methyl-4-benzoylpyrazol-5-one-tetraphenylmethylenediphosphine dioxide and 1-phenyl-3-methyl-4-benzoylpyrazol-5-one-trioctylphosphine oxide, the distribution factors of Eu(III) and Am(III) showed a synergistic effect owing to adduct formation.

Capabilities of liquid-liquid extraction systems without organic solvents have been examined. Ternary poly(ethylene glycol)-inorganic salt-water systems have been proposed for extraction of complexes of metals with water-soluble organic reagents and inorganic ligands.

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).

The distribution of lanthanides and actinides in a two-phase liquid system obtained by mixing an aqueous solution of poly(ethylene glycol) and ammonium sulfate has been studied as a function of pH. Conditions are reported which provide the heterogeneity of the system suggested. It is shown that thorium and plutonium can be separated from transplutonium elements and lanthanides. Conditions have been chosen for quantitative group extraction of actinides and lanthanides.

1. In contrast with sulfides of lead, zinc, and antimony (III), in the case of activation of tin (IV) sulfide with copper (II), the sorbed copper is present in the II oxidation state. 2. When diethyldithiocarbaminate reacts with copper sorbed by SnS2, paramagnetic hydrophobic compounds which are firmly attached to the sulfide surface are formed. The compound readily desorbed by chloroform is copper (II) bis-(dithiocarbaminate). The surface compound not desorbed by chloroform also has a chelate structure and apparently corresponds to a copper (II) compound, the coordination sphere of which is formed by two sulfur atoms of dithiocarbaminate and two sulfur atoms of the SnS2 surface. 3. By the example of carboxylic and α-hydroxycarboxylic acids, the authors show the relation between the selectivity of the effect of chelate-forming reagents and the type of their attachment to the mineral surface under flotation conditions.

The possibility of substoichiometric displacement in ion association systems of metal halogenide anions (chlorides and iodides) and extraction reagent cations is demonstrated. Tetrephenylarsonium halogenide, ternary amines and quaternary ammonium halogenides were used as extraction reagents. The method was applied to the determination of several impurities in aluminium by activation analysis.

1. The exchange reactions of 8-hydroxyquinolinates and cupferronates were studied, and the corresponding exchange series were compiled. The sequence of arrangement of the elements in the series coincides with the sequence of variation of the values of Kex1/p. 2. A method was described for determining extraction constants using exchange reactions. 3. Values of the extraction constants were determined for diethyldithiocarbamates of zinc, cadmium, and lead.

The importance of trace-element analysis in geological, biological, environmental and industrial processes has been increasingly recognized. Although modern instrumental methods of analysis have been applied, preliminary enrichment techniques are required to separate the components to be determined from the interfering constituents of the sample1,2. For the separation of inorganic ions contained in natural waters, industrial fluids or dissolved solid materials, solvent extraction, sorption, ion exchange, precipitation and other methods have been used. However, techniques based on a two-phase distribution or on heterogeneous reactions often cause problems because, in contrast with homogeneous reactions, diffusion controlled processes must be used. Until now, no simple, rapid method has been available for the preconcentration and separation of metals in the homogeneous aqueous phase. Here we demonstrate a technique for the enrichment and separation of metals in aqueous solution using soluble non-crosslinked polymers with chelating groups (polychelatogens)3,4 called liquid-phase polymer-based retention (LPR).

A combined extraction-atomic absorption method for the determination of arsenic and phosphorus has been developed. It comprises the dissolution of the alloy in HNO3 (1∶4) + KMnO4 + conc. HClO4 and subsequent separation of arsenic(V) and phosphorus(V) from the matrix by a solvent extraction with a 0.05 M solution of dioctyltin dinitrate in chloroform + butanol. Arsenic is determined directly in the organic layer and phosphorus in the aqueous phase after back extraction with 3 M HCl by electrothermal AAS using the L'vov Platform, with nickel as stabilizing agent, ash temperature 1200‡ C. The chemical interference and background absorption were considerably reduced and best linearity of the calibration graph as well as highest sensitivity of the determination of phosphorus were achieved (rel. standard deviation 0.022). The method was applied to the determination of 10−4–10−1% of arsenic and phosphorus in copper-nickel alloys. The accuracy of the proposed method was checked on two standard reference samples.

The complexation properties of poly(ethyleneimine) were investigated for cobalt, nickel, zinc, cadmium, and copper using membrane filtration. The elution curves of each metal were determined at different pH values in homogeneous phase. Poly(ethyleneimine) was found to be an effective complexing agent and suitable for retention and separation of metals in aqueous diluted solutions.