Polymeric Sorbent Research Articles

Water-compatible poly (hydroxyethyl methacrylate) polymer sorbent for miniaturized syringe assisted extraction of sulfonamides in milk

A simple, convenient, and economic self-assembly miniaturized syringe assisted extraction (mini-SAE) using poly (hydroxyethyl methacrylate) polymer (PHEMA) as sorbent coupled with liquid chromatography was proposed for rapid screening of sulfadiazine (SD) and sulfamonomethoxine (SMM) in milk. The water-compatible PHEMA was synthesized by reversible addition-fragmentation chain transfer precipitation polymerization using trithiocarbonate as chain transfer agent and methanol–water system as reaction medium. The obtained PHEMA sorbent showed good affinity to sulfonamides and was successfully applied as a special sorbent for a mini-SAE device for simultaneous extraction and isolation of SD and SMM in milk samples. Under the optimum condition, good linearity was obtained in a range of 7.0–700ngg−1 (r≥0.9995) and the average recoveries of SD and SMM at three spiked levels were ranged from 85.6 to 100.3% with the relative standard deviations (RSD) ≤6.5%. The presented PHEMA-mini-SAE protocol could be potentially applied as an alternative tool for analyzing the residues of SAs in complicated biological samples.

Synthesis and characterisation of nano-pore antimony imprinted polymer and its use in the extraction and determination of antimony in water and fruit juice samples

A solid phase extraction method using antimony ion imprinted polymer (IIP) sorbent combined with electrothermal atomic absorption spectrometry (ETAAS) was developed for the extraction and speciation of antimony. The sorbent has been synthesised in the presence of Sb(III) and ammonium pyrrolidine dithiocarbamate (APDC) using styrene as the monomer and ethylene glycol dimethacrylate (EGDMA) as the cross linker. The imprinted Sb(III) ions were removed by leaching with HCl (50%v/v) and the polymer was characterised by FT-IR and scanning electron microscopy. The maximum sorption capacity of the IIP for Sb(III) ions was found to be 6.7mgg−1. With preconcentration of 60mL of sample, an enhancement factor of 232 and detection limit of 3.9ngL−1 was obtained. Total antimony was determined after the reduction of Sb(V) to Sb(III). The method was successfully applied to the determination of antimony species in water samples and total antimony in fruit juices.

A new strategy for synthesis of an in-tube molecularly imprinted polymer-solid phase microextraction device: Selective off-line extraction of 4-nitrophenol as an example of priority pollutants from environmental water samples

In this study a novel preparation protocol has been developed for the construction of an in-tube molecularly imprinted polymer-solid phase microextraction (MIP-SPME) device. Open tubular capillaries have been molded from a polymer sorbent imprinted for 4-nitrophenol as target molecule. Different parameters like inner diameter and volume of the polymer, porogen volume, swelling and shrinking effects of the polymer tubes, polymerization time, pH of the sample, extraction time, ‘salting out’ effect and serial connection of the tubes were evaluated and optimized. Particularly, an optimized polymer preparation process and extraction condition enhanced the final extraction recovery of 4-nitrophenol substantially. Using this new MIP-SPME technique with high-performance liquid chromatography-ultraviolet (HPLC-UV) analysis of the extracts, the linear range and the limits of detection and quantification are 0.001–10mgL−1, 0.33μgL−1 and 1.1μgL−1 respectively. At optimized conditions, a mixture of nitrophenols, alkylated and chlorinated phenols spiked into municipal waste water were analyzed to evaluate the matrix effects and cross selectivity of the new MIP capillary tubes.

How to address the sample preparation of hydrophilic compounds: Determination of entecavir in plasma and plasma ultrafiltrate with novel extraction sorbents

Two fast, simple, selective and economical sample preparation methods for the determination of entecavir in biological materials available at low amounts are reported. The choice of optimal extraction techniques was performed with regard to analyte hydrophilicity, sample volumes, selectivity, method recovery and rapidity. The compatibility of the eluate with the hydrophilic interaction chromatography (HILIC) mobile phase was crucial to allow the elimination of the evaporation and reconstitution steps and to obtain acceptable peak shapes.Different types of sorbents were employed for the extraction of two biological materials (plasma and plasma ultrafiltrate). The mixed-mode polymeric sorbent MCX was chosen as a suitable one for the solid phase extraction (SPE) of plasma samples. The analytes were eluted with 1ml of the mixture of 5 % ammonium hydroxide in ACN:water (95:5). Protein precipitation (PP) with 1ml of ACN was used to remove proteins from 500μl of plasma sample prior to SPE extraction. The microextraction by packed sorbent (MEPS) was employed for the cleaning up of plasma ultrafiltrate samples due to very small volumes available for the analysis. MEPS implemented a novel sorbent based on porous graphitic carbon, semi-automatic analytical syringe and a small volume of sample (50μl). The elution step was performed using 100μl of the mixture of 5mM ammonium acetate pH 4.0:ACN (25:75). The MEPS eluate was fully compatible with HILIC mobile phase subsequently used for the analysis of entecavir, unlike SPE eluate, which had to be evaporated and reconstituted in mobile phase.Both analytical methods were validated and demonstrated good linearity in a range 1–100ng/ml (r2>0.9992) for plasma samples and in a range 0.5–100ng/ml (0.9991) for the plasma ultrafiltrate samples. Intra-day accuracy expressed as recovery was within the range from 80–98% for the plasma samples and 97–106% for the plasma ultrafiltrate samples. Inter-day accuracy ranged within 81–106% for the plasma and 95–101% for the plasma ultrafiltrate samples. The intra-day precision expressed as the % of RSD was lower than 4% for both matrices and inter-day precision was lower than 7% for plasma and lower than 17% for plasma ultrafiltrate. Method sensitivity reached LLOQ of 1ng/ml in plasma and 0.5ng/ml in plasma ultrafiltrate samples. The method was applied for the determination of concentration–time profiles of entecavir in plasma of the perfusate for rat kidney perfusion and for the measurement of concentration of entecavir in plasma ultrafiltrate samples. The results should be helpful in the evaluation of excretion mechanism of entecavir.

Quantitative analysis and sorption of cadmium in environmental samples with a functionalized synthetic polymer

Quantitative analysis of cadmium in environmental samples was achieved with a polymeric sorbent synthesized by copolymerization of N,N-dimethylacrylamide and allyl glycidyl ether/iminodiacetic acid as chelating monomers with N,N′-methylenebisacrylamide as cross-linker. The polymer was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis, and scanning electron microscopy. The sorption capacity of the functionalized sorbent was 70 mg g−1. The equilibrium sorption data of Cd(II) on polymeric sorbent were analyzed using Langmuir, Freundlich, Temkin, and Redlich–Peterson models. Based on equilibrium adsorption data, the constants at pH 4.2 and 20 °C were determined for the first three as 0.33 (L mg−1), 17.5 (mg g−1) (L mg−1)1/n, and 12.9 (J mol−1). Recovery of 94% of the metal ion was obtained with 0.5 mol L−1 nitric acid as an eluting agent.

Determination of pesticide residues and related compounds in water and industrial effluent by solid-phase extraction and gas chromatography coupled to triple quadrupole mass spectrometry

Pollution of drinking water supplies from industrial waste is a result of several industrial processes and disposal practices, and the establishment of analytical methods for monitoring organic compounds related to environmental and health problems is very important. In this work, a method using solid-phase extraction (SPE) and gas chromatography coupled to triple quadrupole tandem mass spectrometry (GC-QqQ-MS/MS) was developed and validated for the simultaneous determination of pesticide residues and related compounds in drinking and surface water as well as in industrial effluent. Optimization of the method was achieved by using a central composite design approach on parameters such as the sample pH and SPE eluent composition. A single SPE consisting of the loading on a polymeric sorbent of 100 mL of sample adjusted to pH 3 and elution with methanol/methylene chloride (10:90, v/v) permitted the obtaining of acceptable recoveries in most cases. The concentration factor associated with sensitivity of the chromatographic analysis permitted the achievement of the method limit of detection values between 0.01 and 0.25 μg L(-1). Recovery assays presented mean recoveries between 70 and 120% for most of the compounds with very good precision, despite the different chemical nature of the compounds analyzed. The selectivity of the method, evaluated through the relative intensity of quantification and qualification ions obtained by GC-QqQ-MS/MS, was considered adequate. The developed method was finally applied to the determination of target analytes in real samples. River water and treated industrial effluent samples presented residues of some compounds, but no detectable residues were found in the drinking water samples evaluated.

A New Biosafe Nanocomposite Polymer Sorbent (BNPS) for the Isotopes Sr and Cs: Application for the Decontamination of Highly Radioactive Water

A New Biosafe Nanocomposite Polymer Sorbent (BNPS) for the Isotopes Sr and Cs: Application for the Decontamination of Highly Radioactive Water

Synthesis of molecularly imprinted polymer sorbents and application for the determination of aminoglycosides antibiotics in honey

Aminoglycoside antibiotic (AA)-selective molecularly imprinted polymer (MIP) sorbent was synthesized by polymerization of methacrylic acid and ethylene glycol dimethacrylate in the presence of streptomycin as template molecule. The MIP sorbent was in detail characterized and its performance was evaluated by selecting four model AAs including streptomycin, gentamicin, spectinomycin and dihydrostreptomycin. Relative to non-imprinted polymer (NIP), the MIPs exhibited much higher recognizable capacity and specificity to the AAs and negligible adsorption for non-AAs as well. In combination of hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC–MS/MS), the MIP sorbent-based solid phase extraction (SPE) was able to effectively determine the residue of four model AAs in honey samples with recovery ranging from 90% to 110%. The limit of detection (and the limit of quantitation) of streptomycin, gentamicin, spectinomycin and dihydrostreptomycin was 4.5 (15.0), 2.4 (8.0), 6.0 (20.0) and 1.8 (6.0)μg/kg, respectively. Relative standard deviations of intraday and inter-day assay under three spiked levels were 4.4–12.0% and 6.8–14.6%, respectively.

Adsorption Behavior of Heavy Metal Ions from Aqueous Solution by Soy Protein Hollow Microspheres

Heavy metals have become ecotoxicological hazards owing to their tendency to not degrade but accumulate in the vital organs of biological bodies. Biosorption is now an efficient method to purify industrial wastewater containing toxic heavy metal ions by using biomass as sorbents. In this work, mimicking the fabricating process of “Tofu”, soy protein was heat-denatured and transformed into soy protein hollow microspheres (SPMs) with a diameter of about 4–45 μm, which were then used as biosorbents to remove heavy metal ions in the water system. The trace amount of remaining metal ions was tested by atomic absorption spectroscopy, and the sorption kinetic and isotherm models were calculated and set up to describe the adsorption behavior. The results showed adsorption capacities of Zn(II), Cr(III), Cd(II), Cu(II), Pb(II), and Ni(II) by SPMs at 70 °C of 254.95, 52.94, 120.83, 115.01, 235.56, and 177.11 mg/g, respectively, which are much higher than that of many other natural polymeric sorbents. The pseudofirst-order kinetic model and Freundlich isotherm model were well correlated to the experimental data. Overall, SPMs were efficient sorbents for binding heavy metal ions, and their sorption capacities were dependent on factors like denaturation content, temperature, time, pH, and initial ionic concentration.

Chelating polymeric particles intended for the therapy of Wilson’s disease

Wilson’s disease is a genetic disorder that leads to a high accumulation of copper in multiple organs with subsequent toxic effects. In this paper, a gentle therapy to eliminate harmful copper concentrations in patients with Wilson’s disease is proposed using an oral administration of insoluble polymeric sorbents containing selective chelating groups for copper(II). The sorbents contained triethylenetetramine, N,N-di(2-pyridylmethyl)amine, 8-hydroxyquinoline or 8-hydroxyquinoline-5-sulfonic acid chelating groups bound to a methacrylate-based macroporous support. Nearly quantitative copper(II) uptake within minutes was achieved in buffers modeling the pH range present in the gastric environment (pH 2.0 and 4.0). The sorbents demonstrated chelating selectivity for copper(II) against zinc(II) with ratios of up to 1321. The sorbents demonstrated sufficient stability of the copper complexes against rechelation using studies in a model environment for the small intestine (the presence of chelating amino acids, pH 6.8).

Theoretical Studies of 17-β-Estradiol-Imprinted Prepolymerization Mixtures: Insights Concerning the Roles of Cross-Linking and Functional Monomers in Template Complexation and Polymerization

In this study, computational methods were employed in efforts to elucidate physical mechanisms underlying the ligand selectivity of polymeric sorbents produced through the molecular imprinting of 17-β-estradiol. Previous computational and experimental studies had identified candidate systems applicable to the development of synthetic polymeric receptors for the detection and possible removal of pollutants with endocrine-disrupting properties. Here we present a series of comprehensive molecular dynamics studies of candidate molecular imprinting prepolymerization systems. The results from the studies highlight the role of the cross-linker and the importance of the interplay between functionalities of the various monomers employed in template complexation. The significance of these results for future studies is discussed.

Rapid and Sensitive Analysis of Euonine and Wilforidine in Human Plasma by High-Performance Liquid Chromatography-Atmospheric-Pressure Chemical Ionization-Mass Spectrometry

Euonine and wilforidine are biologically active Tripterygium wilfordii Hook. f. alkaloids. In this paper, a rapid and sensitive high-performance liquid chromatography-mass spectrometry (MS) method was developed and validated for the simultaneous determination of trace euonine and wilforidine in human plasma. An Oasis® mixed-mode cation-exchange polymeric sorbent was used for solid-phase extraction. The separation was carried out on a reversed-phase Zorbax Plus C18 column (50 mm × 2.1 mm, 1.8 μm) by using ammonium acetate (5 mmol/L)/acetonitrile (30/70, v/v) as the mobile phase at a flow rate of 0.7 mL/min. The quantification was carried out via ion trap MS in the positive selected ion monitoring mode using aconitine as an internal standard. Calibration curves showed good linearity ranging from 0.5 to 100.0 μg/L with correlation coefficient values >0.9990. The average recoveries of euonine and wilforidine ranged from 85.4 to 101.0% and 92.0 to 97.5%, respectively. The intra- and interday relative standard deviations were <8.7 and 12.9%, respectively. The limits of quantification for both euonine and wilforidine were 0.5 μg/L, which is suitable in the clinical pharmaceutical research of volunteer patients with rheumatoid arthritis.

Molecularly imprinted solid phase extraction for simultaneous determination of Δ9-tetrahydrocannabinol and its main metabolites by gas chromatography–mass spectrometry in urine samples

In presented paper analytical method based on solid-phase extraction using molecularly imprinted polymer and gas chromatography–mass spectrometry has been developed and validated for the confirmation of THC, THC-OH and THC-COOH in urine samples. Non-covalent molecularly imprinted polymers of THC-OH were prepared using different functional monomers (methacrylic acid, 4-vinylpyridine, and 2-hydroxyethyl methacrylate), ethylene glycol dimethacrylate as a cross-linker and 2,2′-azobis-isobutyronitrile as an initiator of radical polymerization. Analytes were extracted from urine samples using prepared polymer sorbent with highest binding selectivity and capability. Before extraction, urine samples were hydrolyzed with alkaline. Elution was performed with chloroform:ethyl acetate (60:40, v/v). Dry extracts were silylated with BSTFA+1% TMCS. Detection and quantification were performed using gas chromatography–mass spectrometry in single ion recording mode. The developed method was linear over the range from LOQ to 150ngmL−1 for all three analytes. For THC, THC-OH and THC-COOH LOD was 2.5, 1 and 1ngmL−1, and LOQ was 3, 2 and 2ngmL−1, respectively. The precision, accuracy, recovery and matrix effect were investigated at 5, 25 and 50ngmL−1. In the investigated concentration range recoveries were 71.9% for THC, 78.6% for THC-OH and 75.2% for THC-COOH. Matrix effect was not significant (<10%) for all analytes in the concentration range from 5ngmL−1 to 50ngmL−1. Extraction recovery on non-imprinted polymer was relatively high indicating high non-specific binding. Optimized and validated method was applied to 15 post-mortem urine samples.

Extractive fixed-site polymer sorbent for selective boron removal from natural water

Water contamination by boron is a widespread environmental problem. The World Health Organization (WHO) recommends maximum boron concentration of 2.4mgL−1 for drinking water. The paper presents a simple method for preparation of functionalized sheet sorbent for selective extraction of boron from natural water. The pores of commercially available poly(propylene) membrane were functionalized by room temperature in situ crosslinking of poly(vinylbenzyl chloride) with a cyclic diamine piperazine. The precursor membranes were chemically modified with N-methyl d-glucamine which is selective for boron. Characterization of membrane was carried out using scanning electron microscopy (SEM) and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) techniques. The functionalized membrane has been characterized in terms of parameters that influence the sorption of boron from aqueous streams like pH, uptake capacity, contact time, effects of competing ions and reusability. The maximum boron sorption capacity determined experimentally was 28mgg−1. The studies showed that trace concentrations of boron were quantitatively removed from water at neutral pH. The developed fixed site polymer sorbent exhibited high sorption capacity and fast kinetics as compared to various sorbents reported in literature. It was successfully applied for the removal of boron from ground water and seawater samples in presence of high concentration of interfering ions.

Microsized particles of Aza222 polymer as a regenerable ultrahigh affinity sorbent for the removal of mercury from aqueous solutions

This paper reports the preparation and characterization of a microparticulate sorbent based on a novel p-xylylene-peraza[2.2.2]cryptand (Aza222) polymer that exhibits selectivity and high affinity for mercury cations [1–3]. The sorbent particles dispersed into an aqueous suspension were characterized in terms of surface morphology, size distribution, porosity, and surface charge. Based on measured adsorption isotherms, two possible mechanisms of adsorption by this novel sorbent are proposed: high affinity stoichiometric complexation of Hg2+ within the Aza222 cage, which proceeds until the stoichiometric capacity of the sorbent is saturated; then excess mercury removal by nonspecific physisorption onto the surface of the Aza222 polymer. The experimentally determined mercury loading capacity of the sorbent was in accord with stoichiometric calculations at both high (mg/L) and low (μg/L) concentrations, opening possibilities for the use of the polymer for mercury detection or other analytical applications. Desorption studies were carried out and a preliminary study demonstrated that the sorbent is regenerable. The mercury capacity and selectivity of the sorbent in the presence of calcium ions compared favorably against corresponding properties of both a commercial ion exchange resin used for mercury removal and a related but non-macrocyclic polyamine-based polymer. Density functional (B3LYP) calculations using the 6-31G* basis set for light elements (C, H, Li, N, O) and the LANL2DZ effective core potential and basis set combination were used to compute the relative stability constants of the various metal-cryptand complexes. The agreement between theoretical and experimental Ks values, where known, was generally excellent, supporting the prediction of unknowns. Of particular relevance to the experimental work herein, the calculated difference between log KS for Hg2+ vs. Ca2+ ion binding in the hexamethylated peraza[2.2.2]cryptand is 23.0, indicating an overwhelming preference for binding mercury in this all-nitrogen complexant model for the ligand covalently embedded in the Aza222 polymer sorbent.

Surface heterogeneity of porous polymer sorbents

The distribution function of the energy of adsorption (heterogeneity function, χ) was studied for porous polymers using inverse gas chromatography. The heterogeneity functions to-wards n-hexane, n-butanol, and ethyl acetate probes were obtained for four porous polymers prepared by polymerization of styrene and divinylbenzene. The value of c for the polar surface depends on the choice of the test sorbate. The possibility of comparing surface heterogeneity of various porous polymers using the parameter χ was shown.

Polyethyleneimine‐Functionalized Polyamide Imide (Torlon) Hollow‐Fiber Sorbents for Post‐Combustion CO2 Capture

Carbon dioxide emitted from existing coal-fired power plants is a major environmental concern due to possible links to global climate change. In this study, we expand upon previous work focused on aminosilane-functionalized polymeric hollow-fiber sorbents by introducing a new class of polyethyleneimine (PEI)-functionalized polymeric hollow-fiber sorbents for post-combustion carbon dioxide capture. Different molecular weight PEIs (M(n) ≈600, 1800, 10,000, and 60,000) were studied as functional groups on polyamide imide (PAI, Torlon) hollow fibers. This imide ring-opening modification introduces two amide functional groups and was confirmed by FTIR attenuated total reflectance spectroscopy. The carbon dioxide equilibrium sorption capacities of PEI-functionalized Torlon materials were characterized by using both pressure decay and gravimetric sorption methods. For equivalent PEI concentrations, PAI functionalized with lower molecular weight PEI exhibited higher carbon dioxide capacities. The effect of water in the ring-opening reaction was also studied. Up to a critical value, water in the reaction mixture enhanced the degree of functionalization of PEI to Torlon and resulted in higher carbon dioxide uptake within the functionalized material. Above the critical value, roughly 15% w/w water, the fiber morphology was lost and the fiber was soluble in the solvent. PEI-functionalized (Mn ≈600) PAI under optimal reaction conditions was observed to have the highest CO2 uptake: 4.9 g CO2 per 100 g of polymer (1.1 mmol g(-1)) at 0.1 bar and 35 °C with dry 10% CO2/90% N2 feed for thermogravimetric analysis. By using water-saturated feeds (10% CO2 /90% N2 dry basis), CO2 sorption was observed to increase to 6.0 g CO2 per 100 g of sorbent (1.4 mmol g(-1)). This material also demonstrated stability in cyclic adsorption-desorption operations, even under wet conditions at which some highly effective sorbents tend to lose performance. Thus, PEI-functionalized PAI fibers can be considered as promising material for post-combustion CO2 capture.

Insight into the extraction mechanism of polymeric ionic liquid sorbent coatings in solid-phase microextraction

An investigation into the mechanism of extraction for polymeric ionic liquid (PIL)-based solid phase microextraction sorbent coatings is described. Four PIL-based coatings, namely, a poly(1-4-vinylbenzyl)-3-hexadecylimidazolium bis[(trifluoromethyl)sulfonyl] imide (poly([VBHDIM][NTf2])) PIL produced through 2,2′-azo-bis(isobutyronitrile) (AIBN) initiated free-radical polymerization, a UV-initiated poly(1-vinyl-3-hexylimidazolium) chloride (poly([VHIM][Cl])) PIL, and two crosslinked PILs containing the same IL monomers copolymerized with dicationic IL crosslinkers, were investigated. Calibration curves of 1-octanol were plotted in the presence of naphthalene, a model interfering compound, to observe changes in the linear range, sensitivity, and amount of analytes extracted. Results were compared with a polydimethylsiloxane/divinylbenzene (PDMS/DVB) coating and a polyacrylate (PA) coating which are known to extract analytes primarily through adsorption and partitioning mechanisms, respectively. All PIL-based coatings extracted analytes via a non-competitive partitioning mechanism regardless of the extent of crosslinking.

In vitro catheter and sorbent-based method for clearance of radiocontrast material during cerebral interventions

Contrast-induced acute kidney injury is a severe condition resulting from the use of radiology contrast in patients with predisposing factors. We hypothesized that a novel system including a device containing polymer resin sorbent beads and a custom-made suctioning catheter could efficiently remove contrast from an in vitro novel model of circulatory system (MOCS) mimicking the cerebral circulation. A custom-made catheter was built and optimized for cerebral venous approach. The efficiency of a system made of a polymer resin sorbent beads column (CST 401, Cytosorbents) and this particular catheter was tested in the MOCS running a solution composed of 0.9% saline and radio-contrast. During two series of 18 cycles of first-pass experiments we assessed the catheter's suctioning efficiency and the system's ability to clear radio-contrast injected into the MOCS's cerebral arterial segment. We also assessed the functioning and reliability of the MOCS. Mean suctioning efficiency of the catheter was 84% ± 24%. The polymer sorbent column contrast removal rate was initially 96% and gradually decreased with subsequent cycles in a linear fashion during an experiment lasting approximately 90 minutes. The MOCS had a reliability of 0.9946×min(-1) where 1 × min(-1) was the optimum value. A system including a polymer resin sorbent beads column and a custom-made suctioning catheter had an excellent initial efficiency in quickly removing contrast from an artificial MOCS mimicking the cerebral circulation. MOCS is an inexpensive and relatively reliable custom-made system that can be used for training or testing purposes.

Thermoadsorptive separation of DNA by size using a polymeric sorbent

The article describes theoretical aspects of isolation and separation of DNA fragments by size using a polymeric sorbent. On this basis we presented a theoretical model of thermal desorption of DNA fragments of different length. Assuming that, under certain pH, interaction of DNA with the polymer sorbent is of an ion-dipole character and moving dipoles interact with the sorbent according to the Boltzmann distribution with the total charge of the DNA fragment in its pore, the expression for the interaction energy as a function of temperature is obtained. Equating the thermal energy to the interaction energy of the ion-dipole character, we have found the critical temperature of DNA separation from the sorbent. Account of the conformation of single-stranded DNA in the coil form leads to the dependence of DNA separation temperature, i.e., desorption, on the length of the DNA chain. The temperature for desorption increases symbatically to the contour length of DNA.