Селективность разделения в газовой хроматографии определяется природой неподвижной фазы. В рамках предложенной авторами ранее модели межмолекулярных взаимодействий и разработанного на ее основе теоретического метода трехпараметрической характеристики хроматографических неподвижных жидких фаз делается количественная оценка способности молекул к участию в дисперсионных, диполь-дипольных взаимодействиях и в водородных связях. Метод показал свою эффективность при описании свойств неподвижных фаз на основе углеводородов, полиэтиленгликоля, полисилоксанов и ионных жидкостей. Свойства неподвижных фаз и молекул аналитов описываются двумя характеристиками селективности: полярностью и гидрофильностью, которые могут быть рассчитаны по прямой задаче по структурной формуле вещества и по обратной задаче по экспериментальным данным в виде индексов удерживания Ковача или констант Роршнайдера-МакРейнольдса; противоречия между результатами расчета характеристик двумя способами обнаружено не было. С помощью предложенного метода была выявлена связь между молекулярной массой полимерной молекулы и величинами характеристик селективности. Предложена карта селективности как удобный наглядный способ классификации неподвижных фаз, которая может быть применена в сочетании с принципом подобия свойств для выбора наиболее селективной к заданным аналитам неподвижной фазы; этот выбор может быть сделан без проведения экспериментов. Предлагаемая работа посвящена определению обобщенного заряда как первого и ключевого параметра метода трехпараметрической характеристики. Основным инструментом послужила разработанная ранее в лаборатории сорбционных методов ГЕОХИ РАН теория обобщенных зарядов. Эта теория, выведенная из фундаментальных принципов, описывает ван-дер-ваальсовы взаимодействия в виде потенциала Леннард-Джонса с помощью характеристик молекул, определяемых из молекулярной структуры. Ранее с ее помощью были успешно описаны неполярные хроматографические системы. В работе даны определения обобщенных зарядов, показана их связь с физическими и экспериментальными величинами, приведены расчетные формулы для изолированных молекул и для жидких фаз. Представлены результаты детального расчета обобщенных зарядов веществ разных классов, включающих в себя газохроматографические неподвижные фазы.

Abstract A model of the ion hydration shell based on its topological, electrostatic, and hydrophilic properties at an atomic level has been developed. The energy of hydration layer is described taking into account the local dielectric permittivity, layer geometry in the cases of creation and destruction of hydrogen bonds, and the formation of a multilayer hydration shell. An expression for the ion hydration number is derived, which accounts for the ionic radius, charge, and the hydrogen bonding ability of the ion.

The development of nanomaterials designed for enhanced and controlled delivery of metallodrugs is a challenging task and requires using reliable analytical tools. In this bioanalytical study, we employed high-resolution inductively coupled plasma-mass spectrometry to assess a novel type of nanocarrier based on cation-exchanger nanoparticles (CENs). By recording the signals of Pt and S isotopes, it was shown that direct interaction between CENs and activated cisplatin drug results in a fast and high drug loading (up to 0.12 g Pt per gram) and in human serum environment the loaded CENs are rapidly converted into the protein-bound form but do not discharge the payload. To gain an insight into the composition of the protein corona, the relative abundances of proteins attached to the surfaces of parent and cisplatin-loaded CENs were determined using LC-MS/MS. The potential of CENs as a nanocarrier for smart drug delivery has been further confirmed by a sizeable release of cisplatin under conditions relevant to cancer cytosol (but negligible in normal cytosol setting). It is believed that binding to the CENs would provide the cisplatin treatment more targeted action, higher (when necessary) dosages, and possibly reduced side effects.

An approach is developed in which the interaction between the functional group of an ion exchanger and a counterion is presented in the form of the main Coulomb term—the so-called potential of the ion exchanger related to the functional group—and small contributions from the electrostatic and other forces associated with the parameters of the counterion to describe the equilibrium of ion exchange. It is shown that along with the sizes of counterions (which follows from the electrostatic pattern), the coefficients of selectivity are affected by the ability of ions to hydrate. This is expressed in the so-called hydrate defect, i.e., the specific number of water molecules lost by an ion upon transitioning to the ion-exchanger phase. The inversion of the selectivity of ion exchangers as a result of a combination of the effects of Coulomb interaction and hydration is discussed. An non-observational model of the hydration shell of an ion is proposed that considers the ability of the ion to preserve or destroy the local structure of the medium. Quantitative relations are derived for the coefficients of selectivity of ion exchange, the parameters of which are the potentials and swelling of ion exchangers, and the size, charge, and nature of counterions. The correspondence between the calculated and experimental values for alkali metal and ammonium cations is shown using the example of a strongly acid cation exchanger.

We propose a graphical method for classifying phases in gas chromatography using a selectivity map, which is a two-dimensional diagram on the polarity–hydrophilicity coordinates, based on the theoretical description of the selectivity of liquid phases by three-parameter characteristics. The three-parameter characteristic method uses an expression of the intermolecular interaction energy in terms of the contributions of nonpolar, polar, and hydrogen bonds in an asymptotic approximation obtained using the theory of generalized charges and a new quantum-mechanical concept of the energy and probability of hydrogen bond formation. An advantage of the method is that the parameters used in the mathematical expressions have physical meaning, are portable, and can be found without experimentation. Relationships between the characteristics of stationary phases and their structure are revealed. The selectivity map as a classification method enables gas chromatographic liquid stationary phases to be considered in the range from low polarity/low hydrophilic to high polarity/high hydrophilic phases. On the other hand, applying the principle of the similarity of properties in combination with the selectivity map ensures the selection of the most selective phase for the given analytes. This selection can be made a priori, without experimentation. An example is given of choosing a selective stationary phase for separating substances with similar properties using a selectivity map.

A non-empirical model of the electrostatic field in a polar liquid is proposed, which takes into account the effect of dielectric saturation that creates a volumetric distribution of the point charge density. To this effect, the concept of a charge transfer region is introduced into the model, which has a boundary separating the molecules oriented along field force lines from the molecules with randomly oriented dipoles. The model is applied to describe the local static dielectric constant for polar liquids. The theoretical deduction is based on the Poisson equation and energy balance in the process of charge distribution. The universal dependence obtained has been verified with experimental data for aqueous solutions.

The theory of generalized charges is an asymptotic approximation of quantum mechanics for interatomic forces. It is based on the model of multicomponent electron gas, which extends the Thomas–Fermi model of inhomogeneous electron gas to pair electronic states. The present research takes in consideration the participation of the field of generalized charges in interatomic bonds. Herein, the definition of generalized charges (GC) by means of the overlap integral of the wave functions of valence electrons is given, and properties of GC are found out. Equations are derived for the potential and length of a homopolar bond, and dependence of these parameters on the generalized charges is shown. The dissociation energy of a diatomic molecule is expressed in terms of the nuclear charges, the function and multiplicity of the covalent bond, the angular momentum, and the vibrational energy of the binding electrons. The parametrization rules are substantiated and an a priori calculation of the dissociation energy of diatomic homonuclear molecules is carried out against the electronic configuration of the bond electrons and the nuclear charge. The calculation results for homonuclear compounds of the elements of the first four rows of the periodic table are shown to be of satisfactory accuracy.

A study is performed of the effect of forces of different natures have on ion exchange in classical systems that are polymeric ion exchangers in aqueous solutions. A canonical form of the interaction energy is introduced in which the main contribution is made by electrostatic energy. A theoretical analysis is made of experimental data on the electrical conductivity of ion-exchange membranes, allowing for the nature of internal diffusion. A description is given of the dependence of local permittivity on the interionic distance, which is considered when establishing the configuration of ions and water in the region of interaction. The electrostatic potentials of some strong ion exchangers are determined.

A theoretical approach used in the work—the theory of generalized charges—is an asymptotic approximation of quantum mechanics for interatomic forces. To some extent it is similar to the Thomas–Fermi model of inhomogeneous electron gas. The well-known consequence of Teller's theorem about the impossibility of applying the Thomas–Fermi model to interatomic forces is circumvented by replacing the electric field with the field of generalized charges. To clarify the origin of generalized charges, the concept of covalent bond function is introduced through the overlap integral of the electronic wave functions of interacting atoms. The proposed approach is convenient to explain two types of interatomic interactions (covalent and van der Waals) and to derive the expressions for their energies. It is shown that the covalent bond function is involved in the electronic balance and associated with generalized charges and wave vectors of electrons. New analytical relationships, restrictions and regularities for the length and potential of a homopolar covalent bond are deduced. In particular, expressions are obtained for the covalent radii and bond distances of homonuclear molecules in the ground state. The theory of generalized charges also has excellent prospects for describing the binding energy, which will be shown independently.

Based on an analysis of the results of original research performed in the Laboratory of Sorption Methods of the Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences within the project “Mathematical Chromatograph,” the review covers the aim and strategy of the imitation modeling of high-performance chromatography; associated problems of the theory of intermolecular interactions; classifications of polar stationary phases by their selectivity; descriptions of the kinetics and dynamics of sorption processes, choice of the composition of multicomponent mobile phases in HPLC and ion chromatography using the method of the dynamic map of a chromatographic system; and the development of alternating gradient modes using a mathematical experiment.

We proposed a method of cyclic alternating-current voltammetry with track membranes (TM) filled with ion exchangers with asymmetric pores for the determination of acetylcholine chloride (ACC). We studied the electrochemical and performance characteristics of the determination of ACC using track membranes with pores filled with nanoparticles of crushed cation and anion exchangers. Acetylcholine chloride can be determined in concentrations down to 10–6 M.

We propose a new approach to assessing the contamination of tea, coffee, cocoa, and vegetable oils with F-, Cl-, Br- and S-containing organic pesticides and other hazardous anthropogenic and natural compounds at a trace level. The approach ensures the rapid screening of test samples for the total concentration of all halogen and sulfur organic compounds present in the samples. Sample preparation is excluded. The procedure is based on the direct high-temperature oxidative conversion of a test sample under oxygen; the absorption of inorganic salts present in the sample in a reactor; the absorption of the conversion products of organic compounds of the sample, including the analyzed ones, by deionized water with the formation of F–, Cl–, Br– and SO $$_{4}^{{2 - }}$$ anions; and their determination in the absorbate by ion chromatography. This approach ensures the simultaneously reliable determination of all volatile, medium-volatile, and nonvolatile organohalogen and organosulfur compounds present in one sample and, thereby, improves the reliability of detection by eliminating their losses during the analysis.

A methodology is proposed for the highly selective, sensitive, and reliable determination of the total concentration of halogen and sulfur organic compounds in vegetable oils in the presence of inorganic salts, based on the direct high-temperature conversion of an oil sample in a stream of pure oxygen, absorption of inorganic salts in a reactor, absorption of the products of analyte conversion with deionized water to form F–, Cl–, Br–, and S$${\text{O}}_{4}^{{2 - }}$$ anions, and their determination in the absorbate by ion chromatography. An increase in the reliability of the determination of F–, Cl–, and Br– anions is provided by combining the registration of retention times in the direct determination of anions with an analysis of the flow of the same absorbate after the selective removal of F–, Cl–, and Br– anions (together) using corresponding adsorption columns packed with cation exchangers R–Al3+ (for F–) and R–Ag+ (for Cl– and Br–) (possibility of distortion of the determination result of these anions due to potentially coeluted components is excluded). Using the proposed methodology, the total concentration of halogen and sulfur organic compounds is determined in samples of vegetable oils of varying degrees of purity. It ranged from 2 × 10–6 to 6.0 × 10–2% (in terms of element), depending on the sample and element, at a sample volume of 1 μL. A possibility of increasing sample volume by up to 15 times and lowering the limits of detection to 10–7% (in terms of element) is shown.

Рассмотрена модель взаимодействия нейтральных молекул в аморфной изотропной среде, в которой энергия межмолекулярного взаимодействия содержит три независимые группы величин, описывающих неполярные, полярные силы и водородные связи. Каждая из сил представлена своим молекулярным дескриптором — соответственно обобщенным зарядом, дипольным моментом и двумя числами, отражающими способность молекулы быть донором или акцептором водородной связи. Описан вклад водородной связи в общую энергию межмолекулярного взаимодействия как произведение пороговой величины, имеющей квантово-механическую природу, и вероятности правильного расположения взаимодействующих молекул. Развитая модель применена для оценки энергии димеров воды, спиртов и карбоновых кислот, что позволило подтвердить ее корректность. В полной мере правильность и удобство модели проявились в априорном расчете теплоты парообразования воды, спиртов и кислот.