Analysis and occurrence of alkylphenolic compounds and estrogens in a European river basin and an evaluation of their importance as priority pollutants

As a part of a project aiming to assess the potential toxicological effects of contaminants in aquatic ecosystems, the objective of this work was to determine the occurrence of several selected endocrine-disrupting compounds in water and sediment and to estimate the estrogenicity of the water. The study consisted of four sampling campaigns at seven sampling points in the lower Llobregat catchment area (NE Spain). Water and sediment samples underwent chemical target analysis for 19 steroid estrogens and alkylphenols, which are known to be endocrine-disrupting compounds. In this study, the only estrogens detected in the water samples were estrone and estrone-sulfate, which were found at low levels (2–5 ng l⁻¹). The alkylphenolic compound showing the highest concentrations was nonylphenol di-ether carboxylate (NP2EC), which was found at levels up to 30.62 μg l⁻¹ in water samples and 535 ng g⁻¹ in sediment samples. K _d was determined for several alkylphenolic compounds and showed the expected trend of decreasing K _d with increasing polarity. The concentrations of nonylphenol and octylphenol only exceeded the annual average of the European Union’s environmental quality standards (EQS) in one sampling point. However, the calculated estrogenic potential surpassed the expected effect concentration in several sampling points, indicating a potential risk. Therefore, we recommend that future EQS include short-chain alkylphenol ethoxylates and carboxylates.     

Determination of alkylphenols and alkylphenol ethoxylates in sewage sludge: effect of sample pre-treatment

A complete characterization of sewage sludge collected from five biological waste water treatment plants was done to determine physico-chemical parameters, heavy metals and alkylphenols, making special emphasis on sampling, homogenization, and sample pre-treatment. Ultrasonic extraction followed by gas chromatrography coupled with mass spectrometry was used to evaluate the effect of sample pre-treatment (untreated sample, freeze-drying, drying at 40 °C or drying at 100 °C) on the concentration of octylphenol (OP), nonylphenol (NP) and nonylphenol ethoxylates (NP₁EO, NP₂EO). Untreated samples and samples dried at 100 oC gave concentration levels up to 62% and 89% lower, respectively, than freeze-dried samples. In 50% of cases, freeze-dried samples led to significantly higher concentrations than those obtained by drying at 40 °C. Thus, freeze-drying is the recommended sample pre-treatment to prevent possible losses of OP, NP, and NP₁EO. Using this methodology, concentrations detected were from 3.2 to 199 mg kg⁻¹ being NP followed by NP₁EO found in highest concentration. The total concentration of NP and NP₁EO exceeded the limit of 50 mg kg⁻¹ proposed by the draft European directive on sewage sludge in three out of five samples studied. Contrarily, heavy metals were below the legislated values.     

Determination of pharmaceuticals,steroid hormones,and endocrine-disrupting personal care products in sewage sludge by ultra-high-performance liquid chromatography–tandem mass spectrometry

A sensitive method has been developed and validated for the determination of diverse groups of pharmaceuticals, steroid hormones, and hormone-like personal care products in sewage sludge. Samples were extracted by ultrasonic-assisted extraction followed by solid-phase extraction cleanup. For determination of estrogens and hormone-like phenolic compounds, sample extracts were further derivatized with dansyl chloride and purified with silica gel column chromatography to improve the analytical sensitivity. The chemicals were determined by ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS) in multiple-reaction monitoring mode. Recoveries ranged mostly from 63% to 119% with relative standard deviations within 15%. Method quantification limits were 0.1–3 ng g⁻¹ dry weight (dw) for sewage sludge. The method was applied to a preliminary investigation of pharmaceuticals and personal care products (PPCPs) in sewage sludge and sediment in the Pearl River Delta, South China. Triclosan, triclocarban, 2-phenylphenol, bisphenol A, and parabens were ubiquitously detected at 3.6–5088.2 ng g⁻¹ dw in sludge and 0.29–113.1 ng g⁻¹ dw in sediment samples, respectively. Estrone, carbamazepine, metoprolol, and propranolol were also frequently quantified in the sludge and sediment samples. The dewatering process caused no significant losses of these PPCPs in sewage sludge.     

Occurrence of endocrine-disrupting compounds in reclaimed water from Tianjin,China

Continuous disposal of endocrine-disrupting compounds (EDCs) into the environment can lead to serious human health problems and can affect plants and aquatic organisms. The determination of EDCs in water has become an increasingly important activity due to our increased knowledge about their toxicities, even at low concentration. The EDCs in water samples from the reclaimed water plant of Tianjin, northern China, were identified by gas chromatography (GC)–mass spectrometry (MS). Important and contrasting EDCs including estrone (E1), 17β-estradiol (E2), 17α-ethynylestradiol (EE2), 4-tert-octylphenol (OP), 4-nonylphenol (NP), bisphenol A (BPA), di-n-butyl phthalate (DnBP), diisobutyl phthalate (DIBP), and di(2-ethylhexyl)phthalate (DEHP) were selected as the target compounds. Concentrations of steroid hormones, alkylphenolic compounds and phthalates ranged from below the limit of detection (LOD) to 8.1 ng L⁻¹, from <LOD to 14.2 ng L⁻¹, and from 1.00 μg L⁻¹ to 23.8 μg L⁻¹, respectively. The average removal efficiencies for target EDCs varied from 30% to 82%. These results indicate that environmental endocrine disrupting compounds are not completely removed during reclaimed water treatment and may be carried over into the general aquatic environment.     

Presence of nonylphenol, octyphenol and bisphenol a in two aquifers close to agricultural, industrial and urban areas

Active endocrine disruptors (nonylphenol, octylphenol and bisphenol A) were analysed in 2 aquifers and the corresponding surface waters. They are compounds widely used in industrial processes. The objective of this study was to determine the leaching potential of these compounds in groundwaters and to eventually correlate these levels with surface water samples. The areas sampled were agricultural, close to large cities and with an important industrial activity in the surrounding area. Samples (200 mL) were extracted using off-line SPE with polymeric OASIS 60 mg cartridges. Analyses were performed by gas chromatography-mass spectrometry (GC-MS) using selected ion monitoring (SIM) and full scan for quantification and unequivocal identification, respectively. This paper reports the detection limit for the compounds studied (from 0.001 to 0.030 μg L⁻¹), and method performance as regards to linearity (0.01–1.3 μg L⁻¹), reproducibility (less than 9%) and recovery (84 to 95%). The results from a monitoring program revealed the presence of the target compounds in all samples analysed, at levels of 0.07 and 1.9 μg L⁻¹. The presence of these compounds in groundwater was attributed basically to degradation of inert ingredients present in the formulation of many pesticides or to the increasing application of sludge in agricultural practice, although the infiltration of industrial run-off and wastewater disposal cannot be disregarded.     

An analytical method for the simultaneous trace determination of acidic pharmaceuticals and phenolic endocrine disrupting chemicals in wastewater and sewage sludge by gas chromatography-mass spectrometry

This article presents an analytical method based on solid-phase extraction (SPE) and gas chromatography coupled with mass spectrometry for the simultaneous determination of the most frequently used acidic pharmaceutical residues, ibuprofen, diclofenac, naproxen and ketoprofen (KFN), and phenolic endocrine disruptors, bisphenol (BPA), triclosan (TCS), nonylphenol, nonylphenol monoethoxylate and nonylphenol diethoxylate, in wastewater and sewage sludge samples. In the first phase of the study, each compound has been characterized individually and afterwards in mixture as a trimethylsilyl derivative in order to identify the characteristic ions (m/z ratio) constituting the mass spectrum and to choose the ions for quantification and confirmation. Subsequently, derivatization was evaluated by testing different variables such as the volume of the derivatization solvent bis(trimethylsilyl)trifluoroacetamide and the effect of each catalyst, pyridine and 1% trimethyl chlorosilane, in the derivatized solution. For the analysis of wastewater samples, two commercial SPE cartridges, C18 and Oasis HLB, were compared for their extraction efficiency of the target compounds. The key parameter of extraction procedure included the effect of pH (2.5, 5.3 and 7) of the loading solution. For solid samples, parameters such as the extracted biomass, the volume of the extraction organic solvent and the effect of matrix interferences in chromatographic analysis were evaluated. By using C18 cartridges as purification procedure and ultrasound sonication, satisfactory mean relative recoveries with BPA-d16 and meclofenamic acid as surrogates were obtained ranging from 91% to 117% for wastewater and 84% to 107% for sewage sludge samples. Nine-point calibration of the standard mixture was performed by linear regression analysis with a correlation coefficient >0.99 for all the tested compounds. Limits of detection for the developed methods were established between 0.3 (KFN) and 14.8 (BPA) ng L⁻¹, and 15.0 (TCS) and 32.9 (BPA) ng g⁻¹ for wastewater and sewage sludge, respectively. Application to real samples of the wastewater treatment plant in Athens, the capital of Greece, demonstrated the presence of all tested compounds in most of the samples.     

Application of SPME to the determination of alkylphenols and bisphenol A in cyanobacteria culture media

In order to survey the influence of estrogenic compounds on cyanobacteria, solid-phase microextraction (SPME) with a carbowax-divinylbenzene fibre was used for the determination of tert-octylphenol (tert-OP), n-nonylphenol (n-NP), technical nonylphenol (tech-NP) and bisphenol A (BPA) in cyanobacteria culture media by gas chromatography with flame ionization detection. Determinations were carried out without derivatization in deionized water and filtered culture media. A comparison between f2 and Fraquil culture media was performed, which showed that only f2 allowed quantitative recoveries. Headspace SPME with salting out, requiring only 10 mL of sample, was suitable for tert-OP, n-NP, and tech-NP determination with limits of detection (LOD) of <0.05 μg L⁻¹. For BPA, direct immersion SPME could provide a LOD of 1 μg L⁻¹. Automated sampling allowed reproducible extraction. No exudate substances overlapped with the studied compounds during the chromatographic separation and no matrix effects were observed. Ecotoxicity tests can be performed by single spiking of tert-OP and tech-NP and multiple spiking of n-NP due to its lower stability.     

Accelerated solvent extraction then liquid chromatography coupled with mass spectrometry for determination of 4-t-octylphenol, 4-nonylphenols, and bisphenol A in fish liver

Summary Analysis of extracts from fish liver containing alkylphenol contaminants can be hindered by the presence of co-extracted fats and proteins that interfere with chromatographic analysis. In this study accelerated solvent extraction (ASE), Florisil clean-up, then combined liquid chromatography—mass spectrometry (LC-MS) with an electrospray (ESI) interface have been used to optimize an analytical procedure for the analysis of octylphenol, nonylphenol, and bisphenol A in fish liver. After comparison of the efficiency of ASE with conventional Soxhlet extraction the developed procedure was applied to the analysis of liver samples. Calibration plots of the relationship between concentration and the ratio of the responses to the analyte and to the internal standard, 4-n-nonylphenol, were determined by linear regression analysis over the concentration range 0.05 to 10 ppm and resulted in good fits (r ²>0.994). Recoveries (evaluated for each liver sample as the ratio between response to the surrogate compound, 4-n-nonylphenol, and that to the internal standard, 4-n-heptylphenol, relative to the same ratio for a reference standard solution) were 53±20%. Under the experimental conditions used in this work the limits of detection (LOD), calculated by use of a signal-to-noise ratio of 3∶1, were 5 ng g⁻¹ for 4-t-octylphenol, 15 ng g⁻¹ for bisphenol A, and 20 ng g⁻¹ for nonylphenol. The method can be satisfactorily applied to screening analysis of octyl-and nonylphenols and bisphenol A in biological samples such as fish liver.     

Comparison of anoxic granulation in USB reactors with various inocula

Anoxic granulation process with four different inocula was monitored in a laboratory post-denitrification up-flow sludge bed (USB) reactor. Wastewater containing 20 mg L⁻¹ NO₃-N and methanol as an organic carbon source was used. Gradual increase of mass volumetric loading (B _v) and hydraulic loading (γ) resulted in spontaneous granulation of anoxic biomass both from flocculant activated sludge and from anaerobic granulated sludge. With flocculant activated sludge as the inoculum, anoxic granules sedimentation properties and maximum loadings of the USB reactor depended on the sludge volume index (SVI) of the inoculum. B _v,max achieved in the USB reactor with flocculant inoculum from a municipal wastewater treatment plant (SVI = 208 mL g⁻¹) was only 4.2 kg of COD per m³ per day and 0.7 kg of NO₃-N per m³ per day. B _v,max using flocculant inoculum from an industrial wastewater treatment plant (SVI = 170 mL g⁻¹) was 8.1 kg of COD per m³ per day and 1.35 kg of NO₃-N per m³ per day. With anaerobic granulated inoculum (SVI range 8–11 mL g⁻¹), markedly higher loadings in the USB reactor and lower SVI values of anoxic granulated biomass were achieved. Values of B _v,max were in the range of 16.1–22.4 kg of COD per m³ per day and of 2.7–3.7 kg of NO₃-N per m³ per day (depending on the inoculum and the granulation procedure). It was proved that anaerobic granulated sludge is not just an inoculum, it is also a carrier for new denitrification biomass.     

Thiocyanate-selective electrode based on N-salicylidene-benzylamineato copper(II) complex

Highly selective poly(vinyl chloride) (PVC) membrane electrode based on N-salicylidene-benzylamineato copper(II) complexes [Cu(SBA)₂] as new carriers towards thiocyanate-selective electrode was reported. The influence of membrane composition, pH and possible interfering anions were investigated on the response properties of the electrode. The resulting electrode exhibits anti-Hofmeister selectivity sequence: SCN⁻ > ClO₄⁻ > Sal⁻ > I⁻ > Br⁻ > NO₃⁻ > NO₂⁻ > SO₃²⁻ > H₂PO₄⁻ > Cl⁻ > SO₄²⁻, and a near-Nernstian potential linear range for thiocyanate from 1.0 × 10⁻¹ to 9.0 × 10⁻⁷ M with a detection limit of 7.0 10⁻⁷ M and a slope of , over a wide pH range of 3.0–9.0 in phosphate buffer solution at 20°C. The proposed electrode has a fast response time of about 5–10 s and can be used for at least 3 months without any considerable divergence in potential. The electrode was successfully applied to the determination of thiocyanate in waste water and human urine and saliva samples. Published in Russian in Elektrokhimiya, 2008, Vol. 44, No. 3, pp. 293–299. The text was submitted by the authors in English.     

Thermal study of mononuclear Pd(II) complexes of the type [Pd(X)<Subscript>2</Subscript>(Rtu)(PPh<Subscript>3</Subscript>)] (X = Cl,SCN; Rtu = <Emphasis Type="Italic">N</Emphasis>-methylthiourea, <Emphasis Type="Italic">N</Emphasis>-phenylthiourea)

The synthesis, spectroscopic characterization, and thermal analysis of the compounds [Pd(X)₂(mtu)(PPh₃)] (X = Cl⁻ (1), SCN⁻ (2); mtu = N-methylthiourea; PPh₃ = triphenylphosphine) and [Pd(X)₂(phtu)(PPh₃)] (X = Cl⁻ (3), SCN⁻ (4); phtu = N-phenylthiourea) are described. The thermal decomposition of the compounds occurs in two, three, or four stages and the final decomposition products were identified as Pd⁰ by X-ray powder diffraction. The thermal stability order of the complexes is 4 > 3>2 > 1.     

Chemical monitoring and occurrence of alkylphenols, alkylphenol ethoxylates, alcohol ethoxylates, phthalates and benzothiazoles in sewage treatment plants and receiving waters along the Ter River basin (Catalonia, N. E. Spain)

This study presents a quantitative estimation of the analysis and fate of several emerging pollutants, some of them endocrine-disrupting compounds, in surface water samples collected at several locations along the Ter River and two of its tributaries. Influent and effluent waters and particulate matter from five sewage treatment plants (STP) that discharge into these rivers were also studied. The target compounds analyzed were: nonylphenol ethoxylates (NPEO), nonylphenol (NP), octylphenol (OP), bisphenol A (BPA), phthalates, alcohol ethoxylates (AEO) and benzothiazoles. Chemical analysis by liquid chromatography–mass spectrometry using an electrospray interface (LC–ESI–MS) revealed the presence of low amounts (between 0.06 and 17.5 μg L⁻¹) of the target compounds NPE₁₊₂O and NP, which were detected in 100% and 84% of the samples respectively. Maximum concentrations occurred in the STPs associated with the municipalities of Vic and Girona. From the fate and behavior data obtained for the various compounds analyzed in the STP influent and effluent, we can conclude that the STPs are effective at removing large amounts (more than 70%) of the compounds studied from the water.      

The synthesis of13N-labelled nitrite of high specific activity and purity

An improvement in a method for the synthesis of¹³NO ₂ ⁻ from¹³NO ₃ ⁻ with specific activity>30 mCi/mL and radiochemical purity>99% is described.¹³NO ₃ ⁻ is produced by the¹⁶O(p, α)¹³N reaction using a recirculating water target and 20 MeV protons.¹³NO ₂ ⁻ is synthesized by reduction of¹³NO ₃ ⁻ in a cadmium-copper column. Contaminating¹³NH ₄ ⁺ is removed by rotatory evaporation at pH>11.0. The synthetic procedure takes less than 20 minutes from collection of irradiated target water to sterilization of the radiopharmaceutical.     

Solid phase microextraction of volatile organic compounds using carboxen-polydimethylsiloxane fibers

Summary A new 80 μm Carboxen-polydimethylsiloxane (PDMS) fiber for solid phase microextraction (SPME) was tested for the enrichment of volatile organic compounds from water and air. Detection limits between 13 ng L⁻¹ (CH₂Cl₂) and 0.1 ng L⁻¹ (CHCl₂Br and CHClBr₂) for the combination: Carboxen-PDMS fiber and GC-ECD and between 35 ng L⁻¹ and 45 ng L⁻¹ (BTEX compounds) for the combination: Carboxen-PDMS and GC-FID using the headspace procedure were determined. Comparisons with the 100 μm PDMS fiber and further coatings show the advantages of the Carboxen-PDMS fiber with respect to extraction efficiency. Disadvantages of the new fiber compared with the 100 μm PDMS fiber are poorer repeatability and prolongation of equilibrium time. Distribution coefficients of the BTEX compounds between aqueous solution and SPME fiber coating were calculated and compared with the results of other researchers and with octanol-water partition coefficients.     

A novel colorimetric sensor for anions recognition based on disubstituted phenylhydrazone

Hydrazone-based receptor containing electron-withdrawing chromogenic substituents 1,10-phenanthroline-2,9-di-carboxaldehydic-(2,4-dinitrophenyl)-hydrazone (1) has been synthesized. The interaction with different anions via hydrogen bonding was demonstrated by UV-Vis absorption spectroscopy to give a purple 1:1 complexes in DMSO, whose association constant decreases in line with the following order of the studied anions (AcO⁻ > F⁻ > H₂PO₄ ⁻ > OH⁻ >>Cl⁻∼Br⁻∼I⁻). As a naked-eyes colorimetric sensor for anions, the study has a latent application importance.      

The reactivity of ketyl and alkyl radicals in reactions with carbonyl compounds

A parabolic model of bimolecular radical reactions was used for analysis of the hydrogen transfer reactions of ketyl radicals: >C·OH+R¹COR²→>C=O+R¹R²C·OH. The parameters describing the reactivity of the reagents were calculated from the experimental data. The parameters that characterize the reactions of ketyl and alkyl radicals as hydrogen donors with olefins and with carbonyl compounds were obtained: >C·OH+R¹CH=CH₂→>C=O+R¹C·HCH₃; >R¹CH=CH₂+R²C·HCH₂R³→R²C·HCH₃+R²CH=CHR³. These parameters were used to calculate the activation energies of these transformations. The kinetic parameters of reactions of hydrogen abstraction by free radicals and molecules (adelhydes, ketones, and quinones) from the C−H and O−H bonds were compared. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2178–2184, November, 1998.     

Multiresidue procedures for determination of triazine and organophosphorus pesticides in water by use of large-volume PTV injection in gas chromatography

Summary Two procedures, based on large-volume injection with a programmed-temperature vaporizer (PTV), have been developed for the determination of several triazine and organophosphorus pesticides. The use of PTV for injection in gas chromatography (GC) has enabled the introduction of up to 200 μL sample extract into the GC, thus increasing the sensitivity of the method. PTV injection has been combined off-line with two different microextraction procedures—liquid-liquid partition and solid-phase extraction. A simple and rapid off-line liquid-liquid microextraction procedure (5 mL water/1 mL methyltert-butyl ether) was applied to surface water samples spiked at levels between 0.01 and 5μg L⁻¹. Recoveries of the overall procedure were >80% and the precision was better than 15%. Detection limits were <30 ngL⁻¹ from 200-μL injections in GC-NPD analysis of triazines and GC-FPD analysis of organophosphorus pesticides. Off-line automated solid-phase extraction with C₁₈ cartridges has been applied to water samples (50 mL) spiked at 0.01, 0.1 and 1 μg L⁻¹. The overall procedure was satisfactory (recoveries >80% and coefficients of variation <12%) and the limits of detection ranged from 1 to 9 ng L⁻¹. Finally, several surface water samples were anlysed, and triazine herbicides were detected at concentrations of approx. 0.1–0.2 μg L⁻¹. The results were similar to those obtained by conventional solvent extraction then GC-MSD after splitless injection of 2 μL.     

Extraction of HCl,HBr, HNO3, HClO4, H2SO4 and CH3COOH by 4-(5-Nonyl)pyridine and 2-hexylpyridine in benzene and determination of their pKBH+ values

The extraction of HCl, HBr, HNO₃, HClO₄, H₂SO₄ and CH₃COOH into solutions of 4-(5-nonyl)pyridine (NPy) and 2-hexylpyridine (HPy) dissolved in benzene has been studied. The results show that the larger, less basic anions extract better (ClO ₄ ⁻ >CH₃COO⁻≥NO ₃ ⁻ >Br⁻>Cl⁻>HSO ₄ ⁻ ) due to their low aqueous hydration. The ionization constants of NPyH⁺ and HPyH⁺ as determined spectrophotometrically were found to be 5.97±0.06 and 5.94±0.05, respectively, at 25°C.     

Polar herbicides,pharmaceutical products,perfluorooctanesulfonate (PFOS), perfluorooctanoate (PFOA), and nonylphenol and its carboxylates and ethoxylates in surface and tap waters around Lake Maggiore in Northern Italy

A survey of contamination of surface and drinking waters around Lake Maggiore in Northern Italy with polar anthropogenic environmental pollutants has been conducted. The target analytes were polar herbicides, pharmaceuticals (including antibiotics), steroid estrogens, perfluorooctanesulfonate (PFOS), perfluoroalkyl carboxylates (including perfluorooctanoate PFOA), nonylphenol and its carboxylates and ethoxylates (NPEO surfactants), and triclosan, a bactericide used in personal-care products. Analysis of water samples was performed by solid-phase extraction (SPE) then liquid chromatography–triple-quadrupole (tandem) mass spectrometry (LC–MS–MS). By extraction of 1-L water samples and concentration of the extract to 100 μL, method detection limits (MDLs) as low as 0.05–0.1 ng L⁻¹ were achieved for most compounds. Lake-water samples from seven different locations in the Southern part of Lake Maggiore and eleven samples from different tributary rivers and creeks were investigated. Rain water was also analyzed to investigate atmospheric input of the contaminants. Compounds regularly detected at very low concentrations in the lake water included: caffeine (max. concentration 124 ng L⁻¹), the herbicides terbutylazine (7 ng L⁻¹), atrazine (5 ng L⁻¹), simazine (16 ng L⁻¹), diuron (11 ng L⁻¹), and atrazine-desethyl (11 ng L⁻¹), the pharmaceuticals carbamazepine (9 ng L⁻¹), sulfamethoxazole (10 ng L⁻¹), gemfibrozil (1.7 ng L⁻¹), and benzafibrate (1.2 ng L⁻¹), the surfactant metabolite nonylphenol (15 ng L⁻¹), its carboxylates (NPE₁C 120 ng L⁻¹, NPE₂C 7 ng L⁻¹, NPE₃C 15 ng L⁻¹) and ethoxylates (NPE _n Os, n = 3-17; 300 ng L⁻¹), perfluorinated surfactants (PFOS 9 ng L⁻¹, PFOA 3 ng L⁻¹), and estrone (0.4 ng L⁻¹). Levels of these compounds in drinking water produced from Lake Maggiore were almost identical with those found in the lake itself, revealing the poor performance of sand filtration and chlorination applied by the local waterworks.     

The nature of ion exchange selectivity of phenol-formaldehyde sorbents with respect to cesium and rubidium ions

The structure of aqua complexes of alkali metal ions Me⁺(H₂O) _n , n = 1−6, where Me is Li, Na, K, Rb, and Cs, and complexes of 2,6-dimethylphenolate anion (CH₃)₂PhO⁻ selected as a model of the elementary unit of phenol-formaldehyde ion exchanger with hydrated alkali metal cations Me⁺(H₂O) _n , n = 0−5, was studied by the density functional method. The energies of successive hydration of the cations and the energies of binding of alkali metal hydrated cations with (CH₃)₂PhO⁻ depending on the number of water molecules n were calculated. It was shown that the dimethylphenolate ion did not have specific selectivity with respect to cesium and rubidium ions. The energies of hydration and the energies of binding of alkali metal cations with (CH₃)₂PhO⁻ decreased in the series Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺ as n increased. The conclusion was drawn that the reason for selectivity of phenol-formaldehyde and other phenol compounds with respect to cesium and rubidium ions was the predomination of the ion dehydration stage in the transfer from an aqueous solution to the phenol phase compared with the stage of binding with ion exchange groups.