Ionic Strength Values Research Articles

BUFFER SOLUTIONS BASED ON TAURINE

The acid-base interaction in the aminoethanesulfonic acid (taurine, Tau) – potassium aminoethanesulfonate – water system was studied by pH-, redox- and conductometric methods in the temperature range 293–313 K. The ion-molecular composition of NH2CH2CH2SO3H –NH2CH2CH2SO3K – H2O system was calculated. It is shown aminoethanesulfonic acid in aqueous solutions to exist at the ratio CKOH/QTau < 0.5 mainly in the zwitterion form similar to systems with glycine, aminomethanesulfonic acid and its N‑alkylated derivatives. The content of the aminoethanesulfonate anion is directly proportional to the CKOH/QGly ratio. The studied system ionic strength and acid-base dissociation constant for the second stage of the aminoethanesulfonic acid concentration and temperature dependences were determined. The ionic strength values at the isoelectric point (mi.p.)are directly proportional to С0Tau and practically do not depend on the temperature within the error for the same series С0Tau and С0KOH .The pH limits of the buffer action are determined and the buffer capacity of these systems is estimated. It has been established that effective buffer zones of Tau aqueous solutions can to maintain acidity in the higher then physiological pH range at temperature range 293–313 K. The buffer capacity of NH2CH2CH2SO3H – NH2CH2CH2SO3K – H2O system exceeds the analogous values of YNHCH2SO3H – YNHCH2SO3K – H2O (Y = H, CH3, CH2CH2OH, C(CH3)3 and C2H5C6H5) systems. The obtained data on the buffer capacity of the aminoethanesulfonic acid – potassium aminoethanesulfonate – water system can be used in chemical analysis, microbiological and biochemical studies, and the acidity data of the solutions studied can simulate the chemisorption of acid gases (carbon and sulfur dioxides).

The Influence of Temperature, Storage Conditions, pH, and Ionic Strength on the Antioxidant Activity and Color Parameters of Rowan Berry Extracts.

Recent trends in the food industry combined with novel methods in agriculture could transform rowan into a valuable raw material with potential technological applications. Thus, the aim of this research was to investigate the content of bioactive compounds in its fruits and to assess the color and antioxidant stability of the extracts prepared from such fruits during various thermal treatments and at different pH and ionic strength values. Various spectrophotometric methods, HPLC, and capillary electrophoresis were used to quantify the concentrations of bioactive compounds—polyphenols, carotenoids, organic acids, and to assess antioxidant activity and color. The results show that rowan berries contain circa 1.34–1.47 g/100 g of polyphenols among which include catechin, epicatechin, ferulic acid methyl ester, procyanidin B1, etc.; ca 21.65 mg/100 g of carotenoids including zeaxanthin, β-cryptoxanthin, all-trans-β-carotene, and various organic acids such as malic, citric, and succinic, which result in a high antioxidant activity of 5.8 mmol TE/100 g. Results also showed that antioxidant activity exhibited high stability when the extract was subjected to various thermal treatments, pHs, and ionic strengths, while color was mainly impacted negatively when a temperature of 100 °C was employed. This data confirms the technological potential of this traditional, yet often overlooked species.

High stability amino-derived reversed-phase/anion-exchange mixed-mode phase based on polysilsesquioxane microspheres for simultaneous separation of compound drugs

A series of amino-derived mixed-mode chromatographic stationary phases were synthesized based on porous mercaptopropyl-functionalized polysilsesquioxane mesoporous microspheres synthesized by a co-condensation of methyltrimethoxysilane (MTMS) and mercaptopropyltrimethoxysilane (MPTMS). Through controlling the ratio of MTMS and MPTMS, the modified stationary phases with different amino densities were prepared by a “thiol-ene” click chemistry reaction. The morphology, pore structure, and functional groups of the microspheres were characterized by scanning electron microscope (SEM), nitrogen adsorption-desorption test, Fourier transform infrared spectroscopy (FT-IR), elemental analysis, and zeta potential, respectively. The chromatographic behavior of the stationary phases was evaluated by using alkylbenzene homologs and inorganic anions as probes. The mixed-mode retention behavior and separation mechanisms for neutral, alkaline, and acidic drugs on the prepared column had been systematically studied by changing the value of pH, ionic, and solvent strength of the mobile phase. Compared with the silica-based amino-bonded column (S-NH2), the synthesized organosilica phase exhibited higher hydrothermal stability and longer service life under high alkaline conditions. The newly synthesized phase was successfully applied to the simultaneous separation of the multiple substances in compound drugs.

Assessment of commercial porous polyethylene frit for extraction of polycyclic aromatic hydrocarbons from water.

Exploring commercial and inexpensive sorbents for extraction of organic pollutants is still an active area of research. Ultrahigh molecular weight polyethylene sieve plate (UMPESP) is a commercially available, low-cost, and porous frit, which has been widely used in solid-phase extraction cartridges to fix the filling materials. In this work, UMPESP was investigated for the extraction of polycyclic aromatic hydrocarbons (PAHs) from water samples. The desorption and sorption efficiencies of UMPESP were first evaluated and compared with two previously reported sorbents, low-density polyethylene plastic pellet (LDPEP) and silicone rod (SR). The comparative results showed that quantitative desorption of analytes from UMPESP, which could be easily achieved with 2 × 1.5mL n-hexane, was more effective than that of LDPEP (>6 × 1.5mL n-hexane) and comparable to that of SR. Additionally, shorter equilibrium time was rendered by UMPESP (shaking for 120min) compared with SR (>480min), due to the porous structure and larger surface area of the former. Different parameters that affect the extraction efficiency, including organic modifier, ionic strength, and pH value, were then studied. The optimized method coupled with gas chromatography-mass spectrometry afforded good linearity in a concentration range of 10-5000ngL-1 (except acenaphthene in the range of 25-5000ngL-1) with coefficients of determination ranging from 0.9957 to 0.9995 and relative standard deviations below 13.8%. The limits of detection and quantification were 0.04-3.35ngL-1 and 0.13-11.16ngL-1, respectively. Finally, the method was successfully applied to determine PAHs in real water samples, and the results showed no statistically significant difference with the concentrations derived from liquid-liquid extraction.

Contribution to the Understanding of the Interaction between a Polydopamine Molecular Imprint and a Protein Model: Ionic Strength and pH Effect Investigation.

Several studies were devoted to the design of molecularly imprinted polymer (MIP)-based sensors for the detection of a given protein. Here, we bring elements that could contribute to the understanding of the interaction mechanism involved in the recognition of a protein by an imprint. For this purpose, a polydopamine (PDA)-MIP was designed for bovine serum albumin (BSA) recognition. Prior to BSA grafting, the gold surfaces were functionalized with mixed self-assembled monolayers of (MUDA)/(MHOH) (1/9, v/v). The MIP was then elaborated by dopamine electropolymerization and further extraction of BSA templates by incubating the electrode in proteinase K solution. Three complementary techniques, electrochemistry, zetametry, and Fourier-transform infrared spectrometry, were used to investigate pH and ionic strength effects on a MIP’s design and the further recognition process of the analytes by the imprints. Several MIPs were thus designed in acidic, neutral, and basic media and at various ionic strength values. Results indicate that the most appropriate conditions, to achieve a successful MIPs, were an ionic strength of 167 mM and a pH of 7.4. Sensitivity and dissociation constant of the designed sensor were of order of (3.36 ± 0.13) µA·cm−2·mg−1·mL and (8.56 ± 6.09) × 10−11 mg/mL, respectively.

Impact of rice straw biochar addition on the sorption and leaching of phenylurea herbicides in saturated sand column

The application of phenylurea herbicides (PUHs) may lead to the extensive distribution in soils, while the role of straw biochar as a soil amendment on the transport and sorption of PUHs are still unclear. Thus, the transport and sorption behavior of three typical PUHs with rice straw biochar (RSB) was studied in both adsorption simulation experiments of aqueous solution and packed column experiments. The sorption mechanism of RSB to herbicides was investigated through batch sorption studies with three influencing factors including dosage of RSB, pH, and ionic strength (IS) with orthogonal test. The sorption coefficients were improved significantly by increasing the dosage of RSB, while there was no obvious influence by enhancing the pH and IS value. The optimal sorption conditions (pH value at 3, IS at 0.1 M, and RSB dosage at 60 mg) of three herbicides were set and the maximum removal rates of Monuron, Diuron, and Linuron were 41.9%, 25%, and 56.8%, respectively. The co-transport process of RSB and PUHs were investigated under different RSB dosage, pH value, and IS value. The retention effect increased greatly with enhancing the RSB dosage and pH value. However, IS did not have a significant influence on the retention of RSB, and therefore it had little effect on the adsorption capacity, which was consistent with the results of sorption experiments. The breakthrough curves (BTCs) for co-transport were well simulated by the two-site non-equilibrium convection–dispersion equation (CDE). Most of the regression coefficients (R2) were above 0.99, which uncovered the co-transport in packed column were affected by physical absorption and chemical forces. According to the fitting parameters analysis, the RSB particles and PUHs were subjected to a greater resistance and a stronger stability by reducing pH value in porous media. The presence of RSB increased the amount of dynamic sorption sites in the entire co-transport system, which led to a significant promotion of the PUHs' sorption and interception.

Removal of paracetamol from aqueous solution by activated carbon and silica. Experimental and computational study

The presence of pharmaceutical residues in the aquatic environment is a known problem worldwide. Paracetamol is widely used as an analgesic and antipyretic. Its high consumption implies a continuous discharge in aqueous environments through industrial and domestic wastewater that requires mitigation and remediation strategies.The aim of the present study was to analyse the removal of the paracetamol from aqueous solutions using the adsorption technique. For this, three commercial adsorbents with different textural properties were used: two activated carbons (CAT and CARBOPAL) and silica gel. A series of batch adsorption experiments were conducted at different values of pH (3.0, 7.0 and 10.5) and ionic strength (0.01, 0.5 and 1 M) to investigate the effects on the removal of paracetamol from the aqueous solution. In addition, we investigated the adsorption mechanism using the density functional theory.Adsorption was found to be higher in the acidic pH range, as varying pH showed significant influence on the surface charge of the adsorbents and degree of ionization of the paracetamol. Adsorption capacity of the adsorbents increased with an increase in the ionic strength of solution. At 25 °C, pH 3, ionic strength 1 M, 167 mg L−1 of adsorbent and initial concentrations of paracetamol between 25 and 150 mg L−1, the maximum adsorption capacity was 560 mg g−1, 450 mg g−1 and 95 mg g−1, for CAT, CARBOPAL and silica respectively. The experimental kinetic data fitted well the pseudo-second order model and the equilibrium isotherm data the Langmuir model. The functional density theory methods provided atomistic details about paracetamol adsorbed on the surface of carbon and silica through molecular modeling.

An improved model for interpretation of micromixing experiment with iodide–iodate method and sulphuric acid

The Villermaux–Dushman test reaction for micromixing characterization has been used by many researchers to investigate homogeneous mixing systems. Due to the complexity of the iodine-forming reaction, the strong effect of ionic strength of reaction medium on its reaction rate constant, as well as the dependence of the sulfuric acid dissociation on its concentration, the kinetic model of the iodide/iodate test reaction with sulfuric acid is complicated. Therefore, a quantitative evaluation of such a test reaction is challenging and remains an open problem. In this paper, the pH of the sulfuric acid solutions with different values of ionic strength is investigated using the model of Pitzer. The numerical results of the simulation are compared with the experimental data and good agreement is obtained. It is also shown that simple equilibrium calculations for sulfuric acid do not give correct pH results when the ionic strength of its solution is increased by the addition of sulfate salts. However, such an assumption yields satisfactory results for the cases without additional salt and with an acid concentration lower than 0.2 M. Finally, the engulfment model of micromixing using activities to calculate proton concentrations is applied to analyze the experimental results from previous papers employing the iodide/iodate method.

Influence of Ionic Strength on Hydrophobic Interactions in Water: Dependence on Solute Size and Shape.

Hydrophobicity is a phenomenon of great importance in biology, chemistry, and biochemistry. It is defined as the interaction between nonpolar molecules or groups in water and their low solubility. Hydrophobic interactions affect many processes in water, for example, complexation, surfactant aggregation, and coagulation. These interactions play a pivotal role in the formation and stability of proteins or biological membranes. In the present study, we assessed the effect of ionic strength, solute size, and shape on hydrophobic interactions between pairs of nonpolar particles. Pairs of methane, neopentane, adamantane, fullerene, ethane, propane, butane, hexane, octane, and decane were simulated by molecular dynamics in AMBER 16.0 force field. As a solvent, TIP3P and TIP4PEW water models were used. Potential of mean force (PMF) plots of these dimers were determined at four values of ionic strength, 0, 0.04, 0.08, and 0.40 mol/dm3, to observe its impact on hydrophobic interactions. The characteristic shape of PMFs with three extrema (contact minimum, solvent-separated minimum, and desolvation maximum) was observed for most of the compounds for hydrophobic interactions. Ionic strength affected hydrophobic interactions. We observed a tendency to deepen contact minima with an increase in ionic strength value in the case of spherical and spheroidal molecules. Additionally, two-dimensional distribution functions describing water density and average number of hydrogen bonds between water molecules were calculated in both water models for adamantane and hexane. It was observed that the density of water did not significantly change with the increase in ionic strength, but the average number of hydrogen bonds changed. The latter tendency strongly depends on the water model used for simulations.

Graphene oxide transport and retention in biochar media

This study explores the use of biochar (BC), an inexpensive filtration media, for removing graphene oxide (GO) contaminants from the aquatic subsurface environments. Mass balance approaches and column dissection tests were used to analyze the retention behavior of GO in a series of model fixed-bed columns as a function of ionic strength (IS) and flowrate. The column based on the biochar media (BC) displayed 3.6-fold higher retention compared to the quartz sand (control). To overcome the challenges of unfavorable electrostatic interactions between GO and BC, we used a facile functionalization strategy to modify the BC surfaces with nanoscale zero-valent iron (BC-nZVI). The BC-nZVI (5:1, w/w) retained 2.6-fold higher amounts of GO compared with bare biochar. Furthermore, the performance of BC-nZVI increased with decreasing values of IS, attributed to the attachment of GO to nZVI where nZVI was partially dissolved by the presence of higher chloride ion at high IS. A better GO retention (86%) at higher IS was observed in BC where the GO was primarily retained due to the higher aggregation via straining.

Predicting the aggregation tendency of oxidized nanoscale zero-valent iron in aquatic environments.

Predicting the aggregation tendency of nanoscale zero-valent iron (nZVI), oxidized nZVI, in particular, is crucial for the risk assessment of nZVI in aquatic environments. In this study, the comprehensive effects of the pH and ionic strength (IS) on the aggregation behaviors of two highly oxidized nZVIs (HO-nZVI) were examined. Compared with hematite nanoparticles, HO-nZVI presented a sudden acceleration in aggregation under critical conditions; moreover, the morphology of the HO-nZVI aggregates at pH and IS values higher or lower than the critical conditions was significantly different. Furthermore, owing to the differences in magnetization between the two prepared HO-nZVI samples, their critical coagulation conditions were significantly different. The significant changes in the aggregation behavior of the HO-nZVI samples were analyzed using colloidal theories, and the aggregation tendency of HO-nZVI under specific conditions could be simulated by calculating the theoretical critical conditions of aggregation via a method that takes into account the hydrochemical properties, magnetization, and surface charge of HO-nZVI. To examine the correctness of the method, we compared the experimentally determined colloidal stability of HO-nZVI in water samples collected from nearby rivers with the theoretically predicted value. The results indicated that the method was adequate for most situations, except for those in which the hydrochemical properties of the water samples were close to the critical coagulation conditions. Our study proposes a theoretical approach that is viable for simulating the colloidal stability of magnetic nanoparticles in aquatic environments; we anticipate that it will further facilitate the risk assessment of nanoparticles.

THERMODYNAMIC CHARACTERISTICS OF ACID-CORE REACTIONS INTERACTIONS IN THE WATER SOLUTION PIRIDOXAL-5'-PHOSPHATE

As the object of the study, we selected 3-hydroxy-2-methyl-5-(phosphonic) methyl-4-pyridincarboxaldehyde (pyridoxal-5'-phosphate) which is one of the most important biologically active compounds. Direct calorimetric method was used to measure the thermal effects of interaction of the solution of pyridoxal-5'-phosphate with solutions of nitric acid and potassium hydroxide at 298.15K and ionic strength values of 0.5; 1.0 and 1.5 against the background of electrolyte-supporting potassium nitrate. The measurements were carried out in a calorimeter with an isothermal shell equipped with a 60 cm3 reaction vessel and electric calibration at T = 298.15K ± 0.01 К and P = 100.5± 0.7 kPa and automatic recording of the temperature-time curve. Relative measurement error for heats of dissolution of a standard substance was -0.1-0.3%. Close values of constant sequencing of pyridosal-5'-phosphate do not allow to distinguish such an area of pH where only one of the processes of step dissociation would occur. In this regard the total thermal effect of protonation of pyridoxal-5'-phosphate would be measured. Calculation of the equilibrium composition of the system took into account processes step dissociation and water dissociation was carried out according to the KEV program. The thermal effects of stepwise dissociation of pyridoxal-5'-phosphate are calculated using the universal HEAT program. Because, the thermal effects of dilution were measured in three concentration ranges of KNO3: 0.4-0.5;0.9-1.0; 1.4-1.5 mol /l, the number of experiments in each series was at least four. To calculate the confidence interval of the average value of DН Student's criterion was taken at a confidence interval of 0.95 The standard thermal effects of stepwise ionization of pyridoxal-5'-phosphate were found by extrapolation of experimentally obtained amounts of piridoxyxal-5'-phosphate to zero ion force of the solution.

THERMOCHEMICAL STUDY OF ACID-BASE REACTIONS IN AQUEOUS SOLUTION OF PYRIDOXINE

Vitamin B6 is one of the most important vitamins necessary for the life of living organisms. Vitamin B6, which in the body is represented by coenzyme forms - pyridoxal phosphate and pyridoxamine phosphate, is a part of more than 100 enzymes. As the object of study, we chose pyridoxine. The thermal effects of interaction of the solution of pyridoxine with solutions of nitric acid and potassium hydroxide at 298.15K and ionic strength values of 0.25; 0.5 and 0.75 against the background of electrolyte-supporting potassium nitrate were measured with direct calorimetric method. The measurements were carried out in a calorimeter with an isothermal shell equipped with a 60 cm3 reaction vessel and electric calibration at T = 298.15 ± 0.01 К and P = 100.5 ± 0.7 kPa and automatic recording of the temperature-time curve. Relative measurement error for heats of dissolution of a standard substance was -0.1-0.3%. Calculation of the equilibrium composition of the system taking into account processes a step dissociation and water dissociation was carried out according to the KEV program. The thermal effects of dissociation of pyridoxine in a standard solution were found by extrapolating the heats of stepwise dissociation at fixed values of ionic strength to zero ionic strength. Since the thermal effects of dilution were measured in three concentration ranges of KNO3, the number of experiments in each series was at least three. To calculate the confidence interval of the average value of DН the Student's criterion was taken at a confidence interval of 0.95. Standard thermodynamic characteristics (DrH°, DrG°, DrS°) of reactions of acid-base interaction in aqueous solutions of pyridoxine were calculated. With an increase in the background electrolyte concentration, the endothermicity of stepwise pyridoxine ionization processes increases.

Empirical predictor of conditions that support ideal-filter capillary electrophoresis.

Ideal-filter CE (IFCE) is a method for the selection of affinity binders for protein targets from oligonucleotide libraries, for example, random-sequence oligonucleotide libraries and DNA-encoded libraries, in a single step of partitioning. In IFCE, protein-oligonucleotide complexes and unbound oligonucleotides move in the opposite directions, facilitating very high efficiency of their partitioning. For any given protein target and oligonucleotide library, protein-oligonucleotide complexes and unbound oligonucleotides move in the opposite directions only for a limited range of EOF mobilities, which, in turn, corresponds to a limited range of pH and ionic strength values of the running buffer. Rational design of IFCE-based partitioning requires a priori knowledge of this range of pH and ionic strength values, and here we introduce an approach to predict this range for a given type of the running buffer. The approach involves measuring EOF mobilities for a relatively wide range of pH and ionic strength(I) values and finding an empirical predictor function that related the EOF mobility with pH and ionic strength. In this work, we developed a predictor function for a running buffer (Tris-HCl) that is commonly used in CE-based partitioning of affinity binders for protein targets. This predictor function can be immediately used for the rational design of IFCE-based partitioning in this running buffer, while the described approach will be used to develop predictor functions for other types of running buffer if needed.

Stability of melamine‐formaldehyde (MF) resin under different pH and ionic strength values

Melamine and melamine‐formaldehyde (MF) resin are both commonly used materials in food technology. It is shown in this work that the stability of aqueous solutions of MF resins during storage is strongly influenced by the ionic strength and the pH value of the suspending medium. Aggregation phenomena, polymerization, or disintegration of MF resin particles can take place. The critical aggregation concentration (CAC = 1.67 × 10⁻² M KNO₃) and the rate constant kₐₚₚ (1.24 × 10⁻²³ ml/s) for the bimolecular process of aggregation are determined. When the electrolyte concentration is very close to the CAC, the aggregation is slow. By increasing the electrolyte concentration the aggregation process is faster. In high values of ionic strength the aggregation happens almost immediately. At low pH values aggregation phenomena and split of the MF in smaller particles can influence the stability of MF resin particles. For this study, field flow fractionation technique was used. PRACTICAL APPLICATIONS: The present work investigates the role of ionic strength and pH on the stability of melamine. It is shown that aggregation phenomena, polymerization, or disintegration of MF resin particles can take place. Both, aggregation phenomena and split of the MF in smaller particles can influence the stability of MF resin particles at low pH values. These results show that dishes and kitchen utensils made of melamine resins could release melamine when used for acidic foods. The results of this work could be of great importance for both consumers and industry, since they concern preservation, construction, manufacturing, and use of common housewares.

Investigation of Se(IV) diffusion in compacted Tamusu clay by capillary method

For the first time in laboratory, diffusion parameters of Se(IV) in the clay of Chinese Tamusu region(TMS clay) against compacted density, ionic strength and pH value were obtained by capillary method. Diffusion process can be Simplified by using one-dimensional semi-infinite medium diffusion model. The results show a good similarity with the international literature and meet the internationally recognized range of 10−9–10−12. This work will provide data support and theoretical references for the pre-selection of clay rock sites in China’s high-level radioactive waste deep geological repository.

Formation and Cathodic Reduction of Taurine Complexes with Zinc and Nickel(II)

The stability constants of zinc and nickel(II) complexes with taurine have been determined at 25°C and ionic strength values of 0.5; 1.0; and 1.5 (KNO3). The values of thermodynamic stability constants have been calculated. The processes of electrodeposition of zinc–nickel alloys on the 08KP-grade steel from electrolytes with taurine additive and physicochemical properties of coatings have been studied. The effect of the alloy components' ratio on chemical composition and microstructure of the coatings has been demonstrated.

Fractal analysis of the formation process and morphologies of hyaluronan/chitosan nanofilms in layer-by-layer assembly

In the last decade, hyaluronan (HA, polyanion) and chitosan (CHI, polycation) biopolymers have been assembled by layer-by-layer (LbL) for the synthesis of antibacterial coatings. As electrostatic interactions are the main driving force for the formation of LbL films, pH and ionic strength (IS) are important critical variables of synthesis. In this context, we used surface fractal analysis of HA/CHI films to characterize the growth process for different bilayers obtained with two pH (5 and 3) and IS values (0 and 0.1 M NaCl). Our results showed that the HA/CHI assembling is mainly affected by changes in the pH than IS. Fractal dimension (Df) of pH 5 series presented values ~2.2, indicating that irregularities from the initial random adsorption process are minimized. However, when pH decreased to 3, Df increases up to ~2.5, suggesting a transition to diffusion-limited aggregation.

Separation and characterization of millet starch based on asymmetrical flow field-flow fractionation

A method based on asymmetrical flow field-flow fractionation (AF4) coupled with a multi-angle light scattering detector and a differential refractive detector was developed for the separation and characterization of millet starch. In this study, the effects of sample loading, cross-flow rate, half-life, and ionic strength and pH value of the carrier liquid on the AF4 analysis of millet starch were investigated. In addition, the molecular structure of millet starch was determined under the optimum conditions. The optimized operation conditions for the AF4 analysis of millet starch were as follows:injection mass concentration, 0.50 g/L; injection volume, 50 μL; cross-flow rate, 1.2 mL/min; half-life, 3 min; and the carrier liquid, demonized water containing 10 mmol/L pH 7.00 NaNO3 (add 3 mmol/L NaN3). The method developed in this study showed good reproducibility. The relative standard deviations for the radius of gyration (Rg) and molar mass (Mw) were 3.4% and 7.0%, respectively.

Preconcentration of the cobalt using modified forms of the transcarpathian clinoptylolite

The sorption properties of Na- and H-forms of Transcarpathian clinoptilolite towards trace amounts of Co(II) under dynamic conditions were studied. Acid modified samples of clinoptilolite were obtained by treating this zeolite with solutions of different concentrations of nitric, chloride and sulfuric acids. The most effective acid modifier was 0.5 M HNO 3 . The effect of solution pH and pre-treatment temperature of sorbent samples on the sorption capacity of Na- and H-forms of clinoptilolite was investigated. It is established that the highest sorption capacity both modified forms of clinoptilolite occurs from neutral solutions on the the uncalcined samples. The urotropin buffer solution was used to ensure constant value of pH and ionic strength of the solution. The optimal sorption conditions both modified forms of clinoptilolite are as follows: pH 7.0; the flow rate of a solution of Co(II) with a concentration of 0.25 µg·mL –1 through the sorbent – 5 mL·min –1 ; the diameter of the sorbent grains is 0.200–0.315 mm. The maximum sorption capacity of Na- and H-clinoptilolite towards Co(II) are 3.25 µg·g –1 and 2.85 µg·g –1 , respectively, which exceeds the value of the sorption capacity of the natural form of this zeolite 1.5 and 1.3 times. It has been found that the most effective desorbent of Co(II) from the Na-clinoptilolite are HNO 3 solutions, in particular, a 4.5 M HNO 3 solution, which provides 97 % withdrawal of Co(II) from zeolite. The effective desorbents of Co(II) from the H-clinoptilolite are acidic solutions of alkali metals salts. 1 M NaCl solution acidified with hydrochloric acid to pH 4.0 provides 100% withdrawal of Co (II) from acid-modified clinoptilolite. The effect of common water ions on the maximum sorption capacity of Na- and H-clinoptilolite was investigated. The permissible multiple contents (C ion /C Co(II) ) of the common water ions for Na- and H-clinoptilolite are higher 1.5–4 times then for the natural clinoptilolite. The ability of modified forms of Transcarpathian clinoptilolite to sorb trace amounts of Co(II), high sorption capacity and the presence of effective desorbents give a reason to offer these sorbents for purification of water from Co(II) ions, including radioactive isotopes 60 Co, and also for preconcentration of Co(II) ions at the stage of waters samples preparation for analysis. Methods of Co(II) trace amounts preconcentration in the solid phase mode with its further determination using the atomic absorption method are proposed. Keywords: sorption, solid phase extraction, cobalt, Na-clinoptilolite, H-clinoptilolite.