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This article demonstrates possible separation of Pd(II), Pt(IV), and Rh(III) ions from chloride solutions by solvent extraction in rotating coiled columns (RCC). The most common reagents used for extraction of platinum metals were selected as extractants: trioctylamine (TOA), methyltrialkylammonium chloride (MTAA), tributyl phosphate (TBP), and relatively new reagent—N,N,N',N'-tetra-n-octyldiglycolamide (TODGA). The completeness of extraction of platinum metals from individual and mixed hydrochloric acid and chloride solutions has been analyzed as a function of the essence and concentration of extractant, acidity of the analyzed solutions, and other factors. Optimum conditions of quantitative extraction of the metals from model hydrochloric acid and chloride solutions into the extractant phase have been determined, including subsequent selective separation at the re-extraction stage. A flowchart has been proposed for multistage extraction of Pd(II), Pt(IV), and Rh(III) using 0.05 M MTAA solution in toluene as a stationary phase in RCC. The flowchart includes extraction of Pd(II) and Pt(IV) ions from the solution (0.1 M HCl + 30 g/L Cl–) into the organic phase upon simultaneous separation of Rh(III) remaining in the aqueous phase and consecutive re-extraction of Pd(II) and Pt(IV) from the organic phase using 0.01 M solution of thiourea in 0.1 M HCl and 1 M solution of thiourea in 0.5 M HCl, respectively. The flowchart has been verified for separation of platinum metals in the production process of preset composition. The degree of metal extraction after processing by 0.05 M solution of MTAA in in toluene and consecutive re-extraction by solutions of thiourea is 99.5% for rhodium(III), 99.9% for palladium(II), and 97.4% for platinum(IV). The extracted aqueous phases of rhodium and platinum after output from the column did not contain impurities of other platinum metals. In the aqueous fraction of palladium, the platinum content was 0.5%.

For efficient extraction of cyclic amino acids, it has been proposed to use polymers based on N-vinylformamide. The extraction of phenylalanine, tyrosine, histidine, and proline in two-phase systems based on poly-N-vinylformamide and N-vinylformamide–N-vinylimidazole copolymer has been studied for the first time. Systems with the maximum recovery rate of individual amino acids have been found. The mechanism of intermolecular interactions in polymer–amino acid systems has been proposed. The results of extraction of a phenylalanine–tyrosine mixture by a N-vinylformamide–N-vinylimidazole copolymer are reported. An electrophoretic method for determining amino acids in extracts is proposed.

Actively developing “unconventional” methods for the solid-phase extraction (SPE) of organic substances, for example, solid-phase microextraction, solid-phase dynamic extraction, dispersive solid-phase extraction, matrix solid-phase dispersion, microextraction in a packed syringe, etc., are characterized. The main distinctive features of the methods and the fields and prospects for their application are considered. Solid-phase microextraction is most popular, mainly because of a possibility of the full automation of the separation and determination of analytes and the ease of combination with gas and liquid chromatography, as well as with other analytical methods.

The development and use of instrumental methods for the determination of a wide range of trace elements in oil is considered. Special attention is paid to methods of the direct introduction of samples into spectrometers. It is shown that preliminary sample preparation is in certain cases necessary for the determination of trace elements in oil. The main methods of sample preparation of oils, including methods of extraction of a series of trace elements from crude oil (extraction, membrane, sorption, etc.), are described.

A combined approach to the analysis of volcanic ash (VA) was proposed. Ash particles were separated by size using a combination of vibration sieving on sieves (140, 70, 40 μm) and field-flow fractionation in a rotating coiled column (for separation of nano- and submicron particles). Initial samples and obtained fractions were characterized using scanning electron microscopy and static light scattering. Their elemental composition was determined using ICP-MS and ICP-AES methods. The radionuclide composition of the VA was studied by the low-background gamma spectrometry. The studies were carried out by the example of ashes from Puyehue volcano, the Puyehue Cordon Caulle volcanic group, Andes (Santiago, eruption on June, 2011), which were taken immediately after eruption and after first rain. It was shown that up to 15% of major elements (such as P, Ca, and К) and trace elements (such as Be, Hg, Tl, As, Sb, and Bi) could be extracted from the ash by rain and migrate into environment. It was also found that the content of radionuclides (U235, Th234, Pb214, Bi214, Be7) after rain decreases by 30–40%. Of special interest are ash nanoparticles (up to 200 nm), in which the contents of Cu, Pb, Tl, Bi, Sn, As, and Sb are over an order of magnitude higher than the bulk contents of these elements in the ash. This regularity was found in samples taken both prior to and after rain. The proposed methodology of fractionation, study, and analysis of ash particles may be applied for a wide range of soil, ash, and dust samples of different nature.

The properties of a Diasorb-130-IDK sorbent based on silica gel with a grain size of about 6 µm were studied in order to choose conditions for the separation of the rare-earth elements from the samples of natural wine and their subsequent determination by inductively coupled plasma mass spectrometry. The possibility of the quantitative separation of the elements with the use of an ultrasonic flow suspension column was demonstrated. The results were compared with data obtained with the use of other sample preparation methods. A procedure was proposed for the determination of the rare-earth elements and yttrium in the samples of wines.

It is demonstrated that field-flow fractionation using a rotating coiled column (RCC) can be used for the separation and purification of the polydisperse sorbents based on polystyrene–divinylbenzene. The behavior of the sorbent at different operating parameters of RCC was studied. The mobile phase composition, column rotation speed, and the initial flow rate of the mobile phase were selected, optimized for the isolation of a monodisperse fraction with the particle size 4.5 µm and the separation of particles 0.5–2 µm in size, particle fragments, and residues of sorbent synthesis. It is shown that a 15-mL analytical RCC ensures the efficient fractionation of 100 mg of the sorbent in one experiment taking less than one hour with the yield of the desired fraction greater than 95%. The perspectives for scaling up the fractionation in RCC are evaluated; the possibility of using the method for the preparative separation of particles of different nature is discussed.

A method is proposed for the luminescence determination of neptunium in natural waters with the removal of interfering iron. For the separation of iron ionic and colloidal species, solid-phase extraction with N-benzoyl-phenylhydroxylamine as a complexing reagent is used. The method makes possible the reduction of iron concentration in samples by more than two orders of magnitude without noticeable losses of neptunium and, therefore, the attainment of a detection limit for neptunium equal to its value in samples containing no iron.

Nanodiamonds that are obtained during cavitation synthesis in toluene [E. M. Galimov et al., Doklady Phys. 49 (3), 150 (2004)] are investigated. The procedure of chemical purification of nanodiamonds allowing for isolating a chemically pure product is developed, and diamond nanoparticles less than 10 nm in size are obtained. New data indicating that the fcc modification of carbon appears along with the diamond phase under cavitation synthesis and raising the question on the account of interaction types of carbon precursors are represented.

The paper presents the first comparative study of the fractionation of heavy metals, arsenic, antimony, and selenium in soils, sludge and bottom sediments using two systems for dynamic extraction, rotating coiled columns (RCC) and cylindrical microcolumns (MC). It has been revealed that the results of the fractionation of the forms of elements are related with the physicochemical properties of soils, sludge, and bottom sediments and the special features of mixing the sample and eluent in RCC and MC. In particular, it has been demonstrated that, as compared to MC, RCC provides more efficient recovery of the most mobile (ecologically relevant) forms of arsenic, antimony, and selenium from samples rich with organic matter. However, in the majority of cases, despite the different efficiency of the recovery of individual fractions, RCC and MC provide comparable diagrams of the distribution of the extracted forms of elements. The influence of the rate of the eluent flow on the processes of the dynamic extraction of heavy metals, arsenic and antimony in RCC and MC has been estimated. The directions of research for the further harmonization of the methods of dynamic fractionation of forms of elements in soils, sludge, and bottom sediments with different physicochemical mobilities and potential biological availabilities are outlined.

The recovery and separation of plutonium(IV) and americium(III) by solid-phase extraction (SPE) on alkylated silica gel S16 modified with N-benzoylphenylhydroxylamine (BPHA) and with its derivatives was studied. BPHA was modified by introducing into the p-position of the phenyl ring of electronactive substituents that differ in their hydrophobicity: CH3, Ph, Cl, F, and NO2. The SPE of plutonium(IV) and americium(III) was studied in the range of acidities from pH 8 to 1 M HNO3. The recovery and separation of these elements was shown to depend on the nature of the substituent, aqueous acidity, and the preparation of S16 to SPE experiments.

We studied the influence of synthesis parameters and the composition of the reaction mixture on the size and morphology of copper nanoparticles (NPs). Use of a surfactant (polyoxyethylenesorbitan monooleate) is promising for confining NP growth and stabilizing NPs. Concentration ranges of existence were determined for copper NP dispersions stable to aggregation and sedimentation. Scanning electron microscopy and dynamic light scattering were used to show that: the NP size varied from 10 to 65 nm, the average diameter was 25–35 nm, and the shape was spherical. The sizes of copper NP aggregates were determined.

A method for the continuous-flow fractionation of particles in a transverse centrifugal field in a rotating conoidal coiled (RCC) column has been developed. A model of a planetary centrifuge with a conoidal drum of a special construction has been tested. The effects of the rotation and revolution speed of the conoidal RCC, as well as the direction and pumping rate of the mobile phase on the behavior of particles smaller than 1 μm have been studied. The conditions have been selected and optimized for the retention and elution of spherical particles of the ‘150 nm’, ‘400 nm’, and ‘900 nm’ standard samples of silica gel (Polyscience Inc.). The possibility of using RCC for the analysis and production of monodisperse standard particle samples has been demonstrated. In particular, the ‘900 nm’ particles have been separated from admixtures of small (100–200 nm) particles and nonspherical 1–2 μm particles present in the sample. The separated fractions have been characterized by electron microscopy.

Comparative elemental analysis of the Tengiz oil and diesel fuel is performed by inductively coupled plasma mass-spectrometry with autoclave digestion, digestion, dilution with organic solvents, and also rotating coiled columns (RCCs). The advantages and drawbacks of each of the listed sample preparation techniques for the separation of microelements are discussed. In contrast to the other versions, the use of RCCs is shown to provide a unique opportunity to preconcentrating microelements from oil and petroleum products into tiny volumes of aqueous solutions (10 mL of 0.5 M HNO3). The eluate prepared can be used in the subsequent analysis by ICP MS with no extra sample preparation steps. The RCC preconcentration of elements from oil and petroleum products makes it possible to determine metals in concentrations from μg/kg to ng/kg.

Recovery of Np(V), Pu(IV), and Am(III) by solid-phase extraction with supported N-benzoylphenylhydroxylamine (BPHA) from simulated groundwater with pH 8.5 was studied. DIAPAK C16 cartridges modified with BPHA can be used for preconcentration of these elements from natural waters by solid-phase extraction.

The process of geometrical modification of pores in poly(ethylene terephthalate) track-etched membranes (TM) by use of plasma deposition of a fluorine-containing polymer protective layer on one membrane surface and alkali etching of the other surface has been studied in order to produce membranes with improved performance characteristics. Samples of membranes with conical pores have been obtained which have better filtration efficiency compared with initial TM with cylindric pores. Plasma polymerization of 1H,1H,2H-perfluoro-1-octene at the membrane surface was used to produce the protective layer resistant to alkali solutions. The occurrence of plasma modification and changing of pore geometry have been verified by X-ray photoelectron spectroscopy and scanning electron microscopy studies. The filtration efficiency and selectivity of the modified membranes have been studied.

Methods and approaches employed in the fractionation of elements according to their physicochemical mobility and bioavailability in soils, sludges and sediments are generalised. Comparative analysis of sequential extraction schemes for heavy metals, arsenic, selenium and phosphorus is performed. Special consideration is given to the flow-through fractionation and kinetic aspects of selective leaching.

Reinforced track membranes are used for the first time to study element distribution between particles of various sizes and other water components. The properties of the reinforced track membranes are considered. Factors affecting the quality of water in the Volga River in the region of the water intake of the city of Dubna in the Moscow region and potable water in various districts of the city in are characterized by the fractional composition of macro- and microcomponent.

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 separation of Am(III) and Cm(III) by countercurrent chromatography (CCC) was achieved using the liquid phase systems "diamide–hydrogenated tetrapropylene (TPH)–HNO3" following the optimisation of: (i) the compositions of the mobile (HNO3 concentration) and the stationary (nature of the diamide and its concentration in TPH) phases, (ii) column length and (iii) operating parameters of the CCC (flow rate of the mobile phase and rotation speed of the coil column). The following diamide extractants have been studied: (i) N,N´-dimethyl-N,N´-dibutyltetradecylmalonamide (DMDBTDMA), (ii) N,N´-dimethyl-N,N´-dioctylhexyl-ethoxymalonamide (DMDOHEMA) and (iii) N,N´-dimethyl-N,N´-dibutyldodecylethoxymalonamide (DMDBDDEMA). It is shown that these diamides can be used for the separation of Am(III) and Cm(III) by CCC. Increasing the column length leads to an increase of the stationary phase retention on the column while improving the Am/Cm separation. Increasing the speed of rotation of the centrifuge from 660 to 950 rpm also results in increasing the stationary phase retention but does not influence the resolution of the Am/Cm separation. Decreasing the flow rate of the mobile phase from 1.0 to 0.5 mL/min leads to a better resolution of Am and Cm separation. The best Am/Cm separation was achieved with systems based on DMDBDDEMA and DMDOHEMA in TPH using a two-layer coil column and an isocratic elution mode. The application of CCC makes it possible to separate the elements within 100 min: the Cm fraction contains 99.5% of Cm(III) and 0.6% of Am(III) inventories and the Am fraction contains 99.4% of Am(III) and 0.5% of Cm(III).

The retention behavior of suspended solids in rotating coiled columns (RCC) has been studied. It has been shown that the greater the β‐value (ratio of rotation and revolution radii) the better the retention of solid matter. It has also been shown, that up to five grams of a polydisperse soil sample are completely retained in PTFE columns with a total inner capacity of 34 mL (3.2 mm tubing bore) for a wide range of experimental conditions (column rotation speed and mobile phase flow rate). The successful demonstration of the scale‐up of solid suspension retention in RCC, will enhance the capabilities of the accelerated dynamic sequential extraction of trace elements (TE) and other organic and inorganic solutes from solid samples. This will not only be possible for the analysis of samples with elevated TE concentrations, but also for those with slightly elevated or “normal” TE concentrations. PTFE coiled columns have been found to be preferable to stainless steel ones.

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.

A new approach to performing an accelerated sequential extraction of trace elements from solid samples has been proposed. It has been shown that rotating coiled columns (RCC) earlier used in counter-current chromatography can be successfully applied to the dynamic leaching of heavy metals from soils and sediments. A solid sample was retained in the rotating column as the stationary phase under the action of centrifugal forces while different eluents (aqueous solutions of complexing reagents, mineral salts and acids) were continuously pumped through. The procedure developed is time saving and requires only 4–5 h instead of the several days needed for traditional sequential extraction (TSE), complete automation being possible. Losses of solid sample are minimal. In most cases the recoveries of readily bioavailable and leachable forms of Pb, Zn, and Cd are higher, if a dynamic extraction in RCC is used. Since naturally occurring processes are always dynamic, continuous extraction in RCC may help to estimate the contents of leachable forms and their potential risk for the environment more correctly than batch TSE. The Kersten–Foerstner and McLaren–Crawford leaching schemes have been compared, the former has been found to be preferable.

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 possibility of extraction and fractionation of humic acid (HA) in the aqueous biphasic systems (ABS) was shown for the first time. The 10% PEG–10% (NH 4)2SO4–H2O and 5% PEG–7.5% dextran (or dextran sulphate, sodium salt)–H2O systems were used. HA originated from peat, soddy-podzolic soil and chernozem were studied. The distribution coefficients were measured for HA of different origin, size of the molecules, molecular weights (MW) of the polymers and pH of the system. The PEG–(NH4)2SO4–H2O system was found to be better for preconcentration and isolation of HA, whereas the PEG–dextran–H2O system is preferable for HA fractionation. The extractability of HA in ABS increases with increasing the MW of HA molecules. Peat HA are extracted in ABS with higher distribution coefficients compared with chernozem and soddy-podzolic soil HA. It is consistent with higher hydrophobicity of peat HA revealed by hydrophobic interaction chromatography. ABS are promising for HA separation into fractions that differ in their hydrophobic/hydrophilic properties as well as for comparing HA of different origin by their relative hydrophobicity. © 2002 Elsevier Science B.V. All rights reserved.

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.

The effect of physicochemical properties of two-phase liquid systems (interfacial tension and differences in the densities and viscosities of the two phases) on the retention of the stationary phase in a rotating coil column was studied, taking as examples complex liquid systems containing an organic solvent (n-decane, n-hexane, chloroform, carbon tetrachloride and methylisobutylketone), an extracting reagent (di-2-ethylhexylphosphoric acid, tri-n-butyl phosphate, trioctyl amine), water, and a mineral salt (ammonium sulfate). Extracting reagent additions to the organic solvent and salt additions in the aqueous phase lead to changes in physicochemical properties of the liquid system and affect, strongly, the stationary organic phase retention. The influence of the rotational speed on the stationary phase retention for different systems was also investigated. Some recommendations for the selection of proper systems for CCC separations are formulated.

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.

Environmentally significant phosphorus species in water and phosphorus fractions in sediments are briefly discussed and the methods for their determination are described. One of the most critical analytical steps is the separation of the different forms which, after conversion into orthophosphates, may be determined by a multitude of various techniques. Spectrophotometric methods are often preferred for routine analysis. Several rapid automatic methods for the separation and determination of orthophosphate, linear polyphosphates, cyclic condensed phosphates and lower oxidation state anions of phosphorus, which may exist in natural and waste waters, have been developed. They are mainly based on the use of flow-injection analysis, high-performance liquid chromatography including ion chromatography, capillary electrophoresis and a few of other techniques. These methods have been described and critically evaluated.

The present work is an attempt to correlate the composition and some physico-chemical properties of two-phase systems with the stationary phase retention in a coil planet centrifuge of J-type. Complex liquid systems containing an organic solvent (n-decane or chloroform), an extracting reagent (di-2-ethylhexylphosphoric acid, D2EHPA), water and a mineral salt (ammonium sulphate) are considered.

A hypothesis of the mechanism of the retention of one (stationary) phase of a two-phase liquid system in a rotating coil column has been proposed. The balance of forces of different nature acting on the stationary phase retained in the coil column has been considered. The basic equation of the retention process stationarity has been derived. Theoretical dependencies of retention factor on rotational speed for hydrophobic systems and experimental data are in good agreement.

This paper directly links up with Part I [ Spectrochim. Acta 48B , 1365 (1993)] which treats the first application of countercurrent chromatography (CCC) for pre-separation of rare earth elements (REE) in rocks. The rapid and reliable separation and pre-concentration of “light” REE and Y can be achieved using a system of 0.5 mol/l di-2-ethylhexylphosphoric acid (D2EHPA) in n -decane-hydrochloric acid of different concentrations and a planetary centrifuge as a CCC device. However, Tm, Yb and Lu are partially retained in the stationary phase. Comparative data is presented on three other two-phase liquid systems containing trioctylphosphine oxide (TOPO); D2EHPA and TOPO mixtures and diphenyl(dibutylcarbamoylmethylphosphine)oxide (Ph 2 -Bu 2 ) as extractants in terms of their ability for whole REE group complete isolation from the rock constituents. The partial losses of “light” REE (La and Ce) occurred in the system of 0.1 mol/l solution of TOPO in isobutylmethylketone (IBMK) (stationary phase)-1 mol/l NH 4 NO 3 -6 mol/l HCl aqueous solutions (mobile phase). Complete isolution of the entire REE group can be reached in two systems: 0.3 mol/l D2EHPA + 0.02 ml/l TOPO in the solvents mixture (3:1) of n -decane + IBMK, respectively (stationary phase)-1 mol/l NH 4 NO 3 -6 mol/l HCl aqueous solution (mobile phase), and 1.0 mol/l Ph 2 -Bu 2 solution in chloroform (stationary phase)-3 mol/l HNO 3 aqueous solution (mobile phase). The D2EHPA + TOPO mixture is recommended as more economic and accessible.

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.

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.

Solid-phase extraction of plutonium in different individual and mixed oxidation states from simulated groundwater (pH 8.5) was studied. The extraction of plutonium species was carried out in a dynamic mode using DIAPAK C16 cartridges modified by N-benzoylphenylhydroxylamine (BPHA). It was shown that the extent of recovery depends on the oxidation state of plutonium. The extraction of Pu(IV) was at the level of 98–99% regardless of the volume and flow-rate of the sample solution. Pu(V) was extracted by 90–95% and 75–80% from 10- and 100-mL aliquots of the samples, respectively, whereas the extraction of Pu(VI) did not exceed 45–50%. An equimolar mixture of Pu(IV), Pu(V), and Pu(VI) was extracted by 74%. The distribution coefficients (Kd) and kinetic exchange capacities (S) of plutonium in various oxidation states were measured. It was found that during the sorption process, Pu(V) was reduced to Pu(IV) by 80–90% after an hour-long contact with the solid phase. Pu(VI) is reduced to Pu(V) by 34% and to Pu(IV) by 55%. In the case of mixed-valent solution of plutonium, only Pu(V) and Pu(IV) were found in the effluents.

A theoretical approach to the description of metal retention and enrichment in aqueous solution by soluble polymeric reagents during membrane filtration is proposed. The metal retention data obtained experimentally may be explained by using mathematical models based on the theory of kinetics of reactions in partially open systems.

The primary patterns of isolation of actinides from their dioxides with supercritical carbon dioxide containing adducts of tri-n-butyl phosphate and other organic reagents with nitric acid has been investigated. The effective extraction of actinides from their dioxides was achieved using these adducts under common (ambient) conditions without supercritical carbon dioxide, which makes the performance of the process significantly easier. Extraction of uranium and the primary fission products from a simulated spent nuclear fuel has been studied. It was shown that at almost quantitative extraction of U (> 99%), most 95 Zr and 95 Nb (up to 90%) as well as 131 I, partially 103 Ru (∼ 30%), 99 Tc (20%) and lanthanides (up to 10%) also passed into the adduct phase. In this case complete separation of U from 137 Cs, 85 Sr, 140 Ba as well as from the bulk of 140 La, 141-144 Ce and 147 Nd was observed. After dissolution of the adduct containing U and partially fission products in liquid carbon dioxide the extract was transported into a separation column of a planetary centrifuge, and separation of U from remaining fission products was performed by countercurrent chromatography in the dynamic mode.

Methods and approaches employed in the fractionation of elements according to their physicochemical mobility and bioavailability in soils, sludges and sediments are generalised. Comparative analysis of sequential extraction schemes for heavy metals, arsenic, selenium and phosphorus is performed. Special consideration is given to the flow-through fractionation and kinetic aspects of selective leaching.

The separation of various elements by a water-soluble quinolin-8-ol polymer in conjunction with membrane filtration is demonstrated. The method is based on the retention of inorganic ions by a quinolin-8-ol derivative of poly(ethyleneimine) in a membrane filtration cell and subsequent separation of low-molecular-weight species from the polymer complex formed. It is shown that poly(ethyleneimine) and the polymeric quinolin-8-ol derivative can retain metal ions in aqueous solution. The polymer, however, exhibits a much higher retention capability in acidic solution with respect to more highly charged metal ions, such as Zr, Nb, W, Bi, and can therefore be used for separating them from ions that do not form stable quinolinolates. At higher pH, the water-soluble quinolin-8-ol polymer can be applied to the separation and preconcentration of many metal ions. Owing to the hydrophilic nature of the polymer complex in solution, the preseparated elements remain in the aqueous phase, which is convenient for their subsequent determination by AAS, ICP-AES, etc.

The applicability of the three-step BCR leaching scheme to the continuous-flow fractionation of trace metals (TM) using rotating coiled columns (RCC) has been investigated taking soil and sediment reference samples (SRM-2710, CRM-601, BCR-701) as examples. A particulate sample was retained in the rotating column as the stationary phase under the action of centrifugal forces while different eluents, used according to the original and optimised BCR protocols, were continuously pumped through. The whole procedure required 3–4 h instead of at least 50 h needed for the traditional sequential extraction. It has been shown that in comparison with batch sequential extraction procedures (SEP), the recoveries of Cd, Zn, Cu, and Pb at the first stage (most mobile and potentially dangerous acid soluble forms) are somewhat higher, if a dynamic extraction in RCC is used. Nevertheless, the distribution patterns for TM in the first two leachable fractions (acid soluble and reducible forms) are similar in most cases. Since no heating is used in RCC, the recoveries of TM at the third stage (when hydrogen peroxide is applied to oxidize the organic matter) may be incomplete and matrix-dependent. The effect of eluent volume and flow rate on the recovery of TM in different forms has been investigated. It has been shown that the kinetics of heavy metal leaching vary significantly with samples. Hence, investigating the elution profiles can provide additional important information for risk assessment of TM mobilization.

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.

This study exhibits that size fractionation of humic substances (HS) and their metal complexes by ultrafiltration is an efficient procedure for simultaneous determination of stability constants. Using sequential-stage ultrafiltration and a radiotracer technique the HS–Cu and HS–Zn complexes studied can gently be size-fractionated and their free metal fractions simply be discriminated. The conditional stability constants Ki obtained for size fractions of these HS metal complexes exhibit a clear molecular size dependence. Accordingly, the highest Ki values (6.6 for Zn and 6.4 for Cu) are found in the HS fractions of >105 kDa. Moreover, the overall stability constants K found for Cu (log K=5.5) and Zn complexes (log K=4.5) of the aquatic HS complexes studied are quite comparable to those reported in the literature.

A concise overview (75 references) of the analytical fractionation of aquatic humic substances using sequential-stage ultrafiltration is presented. First, humic substances in aquatic environments and actual problems connected with their fractionation and analysis are briefly considered. The molecular size classification of dissolved humic substances by means of multistage ultrafiltration, with special emphasis on on-line techniques, is the focal point of the discussion. In particular, the capabilities of ultrafiltration for the size fractionation and characterization of species formed between colloidal humic substances and pollutants (e.g. metals) are stressed.