Liquid Adsorption Chromatography Research Articles

Polyaromatic hydrocarbons of small reservoirs of the Tomsk region

Relevance. The assessment of the state of natural waters includes the determination of a number of physico-chemical indicators, on the basis of which various indices and classifications are developed. However, they do not take into account a number of pollutants that have a significant impact on the state of the reservoir, for example, polyaromatic hydrocarbons. The article considers some aspects of determining priority pollutants, which include polyaromatic hydrocarbons, according to environmental hazard criteria: toxicity, carcinogenicity, prevalence, frequency of occurrence, source of origin (anthropogenic or natural). Hydrochemical parameters such as pH, dissolved oxygen content, biological oxygen consumption (BPK5), and ion content are taken into account to determine water quality. An attempt was made to assess the impact of polyaromatic hydrocarbons on the ecological state of water bodies and to take into account their contribution to changes in the values of the water pollution index. All these data prove the relevance of the study. Aim. To establish the composition of polyaromatic hydrocarbons in the surface waters of small reservoirs of the Tomsk region to assess anthropogenic load and to show the relationship with the indices of natural water quality. Methods. Extraction, liquid adsorption chromatography, high-performance liquid chromatography, capillary electrophoresis, amperometry, titrimetry. Results. Small lakes of the Tomsk region were studied for the content of 13 polyaromatic hydrocarbons. The authors have carried out the identification by high-performance liquid chromatography with fluorimetric detection. The total content of polyaromatic compounds in the studied surface water samples varies from 0.37 to 0.54 mcg/l. In the polyaromatic hydrocarbons mixture in aqueous samples, there is an increased content of light 2–3 nuclear polyarenes with better solubility (naphthalene, fluorene and phenanthrene), as well as benz[a]anthracene. The content of inorganic components represented by cations and anions does not exceed the maximum permissible concentrations. The water pollution index was calculated; all lakes are moderately polluted, closer to polluted. The paper demonstrates the dependence of the water pollution index coefficient on the content of high-molecular polyaromatic hydrocarbons and the ratio of high-molecular to low-molecular polyaromatic hydrocarbons. It is shown that the higher the value of the water pollution index coefficient, the higher the proportion of difficult-to-oxidize components in surface waters.

Foreign experience in determining the group hydrocarbon composition of petroleum feedstock and petroleum products

Determination of the group hydrocarbon composition (saturated and aromatic hydrocarbons, resins, asphaltenes) of petroleum dispersed systems is predominantly carried out using chromatographic analysis methods: liquid adsorption chromatography, high-performance liquid chromatography, thin-layer chromatography with flame ionization detection. The specificity of standard methods developed for the analysis of petroleum feedstock and petroleum products using a particular method often results in the incompatibility of results both in terms of the nomenclature of the identified hydrocarbon groups and the determined concentration values. This review provides a comparative assessment of chromatographic methods for analyzing the group hydrocarbon composition of petroleum feedstock and petroleum products, their features, advantages, and disadvantages. The main options for modifying standard methods aimed at achieving correlation between the results obtained by different analysis methods are described.

Thermolytic Synthesis of Asphaltene-like Nitrogenous Bases and Study of Their Aggregative Stability

The work is devoted to the study of the influence of nitrogenous bases on the composition of oil and the structure of asphaltenes on their colloidal stability in solution. Model petroleum systems with a basic nitrogen content of 1, 2, and 3% wt. were used as objects of study. Asphaltene-like nitrogenous bases were obtained by thermolysis of model petroleum systems with different nitrogen contents. The results were obtained using elemental analysis, non-aqueous potentiometric titration, spectrophotometry, 1H NMR spectroscopy, and liquid adsorption chromatography. It was established that the content of Nbas in asphaltenes increases by 0.3–1.3% wt. with the increase in quinoline content in petroleum components. Quinoline is incorporated into the supramolecular structure of asphaltenes and increases their average molecular weight by 650 amu. and aromaticity by 2%. The aggregative stability of asphaltenes decreases by 1.5–6 times with an increase in their average molecular weight and an increase in Nbas in their composition as a component of a dispersion medium. The colloidal stability of synthetic asphaltene-like substances, on the contrary, is due to the appearance of their molecular sequence of fragments containing Nbas in aromatic rings.

Online coupling of liquid chromatography and two-dimensional diffusion ordered spectroscopy for the analysis of oligostyrenes

The aim of this study was to introduce a powerful coupling of Liquid Adsorption Chromatography (LAC) and Diffusion-Ordered Spectroscopy (DOSY) for comprehensive structure analysis. This new hyphenation approach facilitated the simultaneous separation of a polymer mixture and the determination of molar masses within a single 3D experiment. The online coupling of High-Performance Liquid Chromatography (HPLC) and two-dimensional DOSY-NMR will be called 3D-LAC-NMR-DOSY experiment. Our methodology enabled the chromatographic separation of analytes based on their chemical heterogeneity, and provided accurate molar masses of the analytes through 2D-DOSY. This new method was demonstrated on a polystyrene oligomer mixture. In this case, the oligostyrenes could be separated with LAC according to their tacticity and chain length in protonated acetonitrile as eluent and DOSY measurements provided the molar masses of each oligomer. In order to show the power of the 3D-LAC-NMR-DOSY method, the comparison to 2D-DOSY, 3D-DOSY and LAC-NMR was separately evaluated. Furthermore, the recently published solvent-independent molar mass calibration of diffusion coefficients was also successfully applied in our LAC-DOSY studies for molar mass predictions of the oligomers in acetonitrile. The predicted molar masses were in good agreement with the LAC-DOSY measurements and were verified by calibrations of diffusion coefficients and mass spectrometry. Finally, this pioneering 3D technique offers a powerful new tool for advancing structure analysis and enhancing our understanding of complex systems such as oligostyrenes.

Changes in composition and structure of nitrogenous bases of resin components of heavy oil from the Nurlatskoe oilfield in the course of thermal decomposition

The relevance. The need to obtain information on heat treatment effect on composition and structure of nitrogenous bases of resin components of heavy oil from the Nurlatskoe field (Republic of Tatarstan) to solve the problems associated with their negative impact on oil refining. The aim. To characterize the composition of nitrogenous organic bases, isolated from the resins of bituminous oil of the Nurlatskoe field, and the products of their thermal cracking. Methods. Complex formation, extraction, liquid adsorption chromatography, potentiometric titration, 1H NMR spectroscopy, structural group analysis, combined gas chromatography-mass spectrometry. Results. Based on a comparative study of the composition and structure of nitrogenous bases of the initial and thermally treated resins of the bituminous oil from the Nurlatskoe field, the authors found out that they both contain high- and low-molecular nitrogenous bases with predominance of high-molecular compounds precipitated by hydrogen chloride. As a result of thermal exposure, the number of such bases increases due to an increase in the proportion of compounds with shorter alkyl substituents in their composition. The method of structural group analysis was used to show that the main directions of thermal transformations of high- and low-molecular bases of resins in Nurlatskoe oil are destruction of alkyl substituents and cyclization of shortened alkyl chains with formation of naphthenic rings. Among the lowest molecular weight bases of the initial resins and thermolysate the authors have identified alkyl-substituted quinolines, benzoquinolines, azapyrenes, thiophenoquinolines, and benzothiophenoquinolines with similar molecular weight distributions. During the thermolysis of resins, the relative content of low molecular weight homologues in the identified nitrogenous bases increases. The share of structures with reduced chromatographic mobility caused by a decrease in the degree of spatial screening of a nitrogen atom increases among similar homologues.

Characterization of chemical composition distribution of ethylene-propylene-diene terpolymers by room temperature liquid adsorption chromatography and comparison to statistical approach

The chromatographic analysis of ethylene-propylene-diene (EPDM) terpolymers has hitherto been carried out only at high temperature, 120–160 °C. However, EPDM terpolymers are amorphous which could potentially allow to study their chromatographic behavior at room temperature (RT). To verify this hypothesis, cloud point measurements were realized to determine prospective solvent candidates. The identified solvents enabled injecting EPDM and model ethylene propylene norbornene terpolymers at RT.The retention of EPDM terpolymers on porous graphitic carbon (PGC) is a function at least two adsorbing comonomer components, ethylene and diene, in all tested chromatographic systems. This makes it difficult to characterize the chemical composition distribution (CCD) of terpolymers, which is of immense technical interest. Therefore, a modified form of LAC (LACm) was employed for determining the CCD of EPDM terpolymers using the identified solvents. Finally, the CCD obtained using different experimental methods was compared to the CCD determined using Monte Carlo simulations.

Determination of End-Group Functionality of Propylene Oxide-Based Polyether Polyols Recovered from Polyurethane Foams by Chemical Recycling.

Chemical recycling of polyurethane foams (PUFs) leads to partially aromatic, amino-functionalized polyol chains when the urethane groups in the PUF structure are incompletely degraded. Since the reactivity of amino and hydroxyl groups with isocyanate groups is significantly different, information on the type of the end-group functionality of recycled polyols is important to adjust the catalyst system accordingly to produce PUFs from recycled polyols of suitable quality. Therefore, we present here a liquid adsorption chromatography (LAC) method using a SHARC 1 column that separates polyol chains according to their end-group functionality based on their ability to form hydrogen bonds with the stationary phase. To correlate end-group functionality of recycled polyol with chain size, LAC was coupled with size-exclusion chromatography (SEC) to form a two-dimensional liquid chromatography system. For accurate identification of peaks in LAC chromatograms, the results were correlated with those obtained by characterization of recycled polyols using nuclear magnetic resonance, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and SEC coupled with a multi-detection system. The developed method allows the quantification of fully hydroxyl-functionalized chains in recycled polyols using an evaporative light scattering detector and appropriate calibration curve.

The occurrence of the cis/trans geometric isomerism of myxoxanthophyll and 4-ketomyxoxanthophyll in the cyanobacterium Anabaena sp. PCC7120.

The cyanobacteria of the genus Anabaena have recently been recognized as a potential source of secondary metabolites of pharmacological and biotechnological importance. In particular, myxoxanthophylls - specific carotenoid glycosides that accumulate in cyanobacterial cells, are attracting increasing interest. Anabaena (Nostoc) sp. PCC7120, a filamentous, mesophilic, nitrogen-fixing cyanobacterium, is a model organism used in biochemical and genetic studies. The carotenoid pool of Anabaena sp. PCC7120 consists of five main species of pigments, namely β-carotene, echinenone, canthaxanthin and two derivatives of myxoxanthophyll: myxoxanthophyll ((3R,2'S)-myxol 2'-fucoside) and 4-ketomyxoxanthophyll ((3S,2'S)-4-ketomyxol 2'-fucoside). Recent findings show that the carotenoid biosynthesis pathway functions in Anabaena sp. PCC7120 cells are affected by environmental factors. Specifically, the balance between β-carotene and ketocarotenoids alters according to the temperature conditions. In this study, a new method, based on single-step liquid adsorption chromatography was developed and applied to separate a fraction containing myxoxanthophyll and 4-ketomyxoxanthophyll from Anabaena sp. PCC7120 cells. It was found that this method allowed a high purity fraction of carotenoid glycosides to be obtained from pigment pools as extracted from cyanobacterial cells. The subsequent analysis using the methods HPLC and LC/MS demonstrated that this fraction consists of a mixture of compounds with different retention times. On the basis of their fragmentation spectra and optical properties, these compounds were identified as geometrical isomers of myxoxanthophyll and 4-ketomyxoxanthophyll, including the dominant all-trans forms and less abundant cis forms. Proposals regarding the structures of myxoxanthophyll isomers are made.

Evaluation of hybrid surface technology for the analysis of the B-group vitamins by LC-ESI-MS/MS

Recently, a novel hybrid surface technology (HST) has been developed to mitigate metal analyte adsorption in liquid chromatography. The HST provides a hybrid organic–inorganic surface on the metal fluidic path, from injection to detector and including the column frits and wall, to mitigate the interaction between analytes and metals. Here the impact of the HST on the analysis of B group vitamins using liquid chromatography coupled with electrospray tandem mass spectrometry (LC-ESI-MS/MS) has been evaluated. Significant improvements in analyte intensity, limit of quantification (LOQ), carry-over, and peak shape were observed using an LC-ESI-MS/MS system and column that incorporated the HST. The key observed improvements include a 3–10 times increase in sensitivity (providing a lower LOQ) for riboflavin, thiamine, nicotinamide, FMN, PLP, and 5MTHF, no carry-over, and a more symmetrical peak for thiamine. When applied to the analysis of B group vitamins in energy drinks and B vitamin dietary supplement samples, the HST system demonstrated excellent accuracy and repeatability.

Influence of Microstructure on the Elution Behavior of Gradient Copolymers in Different Modes of Liquid Interaction Chromatography.

We studied the influence of microstructure on the chromatographic behavior of gradient copolymers with different gradient strengths and block copolymer with completely segregated blocks by using gradient liquid adsorption chromatography (gLAC) and liquid chromatography at critical conditions (LCCC) for one of the copolymer constituents. The copolymers consist of repeating units of poly(propylene oxide) and poly(propylene phthalate) and have comparable average chemical composition and molar mass, and a narrow molar mass distribution to avoid as much as possible the influence of these parameters on the elution behavior of the copolymers. On both reversed stationary phases, the elution volume of gradient copolymers increases with the increasing strength of the gradient. The results indicate that for both modes of liquid interaction chromatography, it is important to consider the effect of microstructure on the elution behavior of the gradient copolymers in addition to the copolymer chemical composition and molar mass in the case of gLAC and the length of the chromatographically visible copolymer constituent in the case of LCCC.

Solvent Selection for Liquid Adsorption Chromatography of Ethylene–Propylene–Diene Terpolymers by Combining Structure–Retention Relationships and Hansen Solubility Parameters

Solvent Selection for Liquid Adsorption Chromatography of Ethylene–Propylene–Diene Terpolymers by Combining Structure–Retention Relationships and Hansen Solubility Parameters

The degradation of poloxamer 188 in buffered formulation conditions

Poloxamer 188 (P188) as a non-ionic surfactant is used in proteinaceous formulations to prevent protein adsorption to hydrophobic surfaces and unfolding at interfaces, preventing the formation of aggregates and particles. Its chemical intactness is crucial to the stability of drug products due to its protecting effects at interfaces. In order to identify and mitigate potential risks that might cause the degradation of P188 during the manufacturing process and storage, in the current work, the stability of P188 was investigated by forced degradation in buffered formulation conditions via oxidation and thermal stress conditions. The process of degradation was monitored through the dedicated liquid adsorption chromatography (LAC) with high sensitivity, and the degradants were characterized by high-resolution mass spectrometry. Results suggest that the vulnerability of P188 is largely related to the buffer conditions. Histidine promotes degradation in the presence of hydroxyl radicals but inhibits the degradation in the presence of H2O2 and alkyl radicals. In thermal stress conditions, histidine protects P188 from degradation at 40 °C, and activates its decay only at higher temperature, like 60 °C.

Исследование влияния состава и структуры сложных оксидов никеля и хрома на облагораживание тяжелой нефти в сверхкритическом водном флюиде

The studies of synthesized oxides Ni–Cr of mixed phase composition were carried out. The relationship between the composition and structural properties of Ni–Cr double oxides on the ratio of Ni2+/Cr3+ cations in the synthesis of their precursors (hydroxides) has been determined. The products of conversion of heavy oil in the presence of Ni–Cr double oxides at a temperature of 380°C and a pressure of 22 MPa in an excess of hydrothermal fluid have been investigated. The influence of oxides on the change in the content of saturated, aromatic hydrocarbons, resins and asphaltenes was shown by the method of adsorption liquid chromatography.

АДСОРБЦИОННАЯ ЖИДКОСТНАЯ ХРОМАТОГРАФИЯ ЭТАНОЛЬНОГО ЭЛЮАТА ЭТАНОЛЬНОГО ЭКСТРАКТА ЗЕЛЁНЫХ ГРЕЦКИХ ОРЕХОВ+ЛИСТЬЯ (LUGLANS REGIA L., СЕМЕЙСТВО ОРЕХОВЫЕ – LUGLANDACEAC) (Сообщение VI)

The aim of the study was to perform column adsorption liquid chromatography in order to obtain ethanol eluate, after preliminary sequential elution of ethanol extract with solvents in the order of their polarity: n–hexane, toluene, chloroform, acetone; to study in detail the chemical composition of this eluate by chromatography-mass spectrometry and X-ray fluorescence spectroscopy, with the intensification of compounds determining the composition of eluate, obtaining their masses -spectra, structural formulas, determination of the nature of trace elements. Materials and methods of research. A detailed study of the chemical composition of acetone eluate of ethanol extract of walnuts+ leaves was carried out using column adsorption liquid chromatography, chromato-mass spectrometry and X-ray fluorescence analysis. The results and their discussion. The features of the chemical composition of ethanol eluate of the product of column adsorption liquid chromatography of ethanol extract were studied, the qualitative composition and quantitative content of compounds identified in the first one were established by chromatography-mass spectrometry. Mass spectra and structural formulas were obtained for 31 individual eluate compounds. Ethanol eluate is characterized by the following indicators of structural and group composition (mass. % of eluate): esters of phthalic acid - 52.14, silicon and sulfur-containing compounds, respectively - 20.19 and 6.43, hydrocarbons - 15.38, glycosides - 2.21, alcohols - 1.92, carboxylic acids - 1.07, sterols - 0.89. It is assumed that the pharmacological effect of ethanol eluate is mainly determined by a set of free carboxylic acids, as well as phthalic acid, formed as a result of biochemical and hydrological transesterification of its esters containing compounds, alcohols, glycosides and sterols. Organosilicon compounds during hydrolysis give silica in the size of nanoparticles, which play the role of carriers of the above compounds to various organs of a living organism, as well as drainage of blood vessels from the products of cell metabolism, for example, cholesterol, various fats, etc. A comparative characteristic of the chemical composition of all ethanol extract eluates was carried out, the effectiveness of column adsorption liquid chromatography was shown.

The development and qualification of liquid adsorption chromatography for poloxamer 188 characterization

Poloxamer 188 (P188) is formulated in proteinaceous therapeutics as an alternative surfactant to polysorbate because of its good chemical stability and surfactant properties, which enable interfacial protection, preventing visible and sub-visible particle formation. However, due to the nature of polymer heterogeneity and limited analytical approaches to resolve the superimposed components of P188, the impact of its quality variance on protein stability is still not well understood. In this study, we developed an analytical method to evaluate the components of P188 as a function of the length of polypropylene oxide (PPO), by maintaining polyethylene oxide (PEO) at the critical point of adsorption (CPA) to eliminate its chromatographic interference. The effectiveness of the separation was confirmed by nuclear magnetic resonance (NMR) spectroscopy and mass spectroscopy (MS) of the individual fractions corresponding to each peak. Additionally, a design of experiments (DoE) and method qualification were carried out to identify and optimize the key operation parameters, including column temperature and evaporative light scattering detector (ELSD) settings that need to be strictly controlled for reliable analytical results. In conclusion, this method is sensitive and reliable to compare the quality variance of commercial P188 and is suitable for routine quality control purposes. The application of this method could help in further understanding the Critical Material Attributes (CMA) that may affect the quality attributes of proteins in formulations.

Transformation of Resinous Components of the Ashalcha Field Oil during Catalytic Aquathermolysis in the Presence of a Cobalt-Containing Catalyst Precursor

The aim of this work was to study the fractional composition of super-viscous oil resins from the Ashalcha field, as well as the catalytic aquathermolysis product in the presence of a cobalt-containing catalyst precursor and a hydrogen donor. The study was conducted at various durations of thermal steam exposure. In this regard, the work enabled the identification of the distribution of resin fractions. These fractions, obtained by liquid adsorption chromatography, were extracted with individual solvents and their binary mixtures in various ratios. The results of MALDI spectroscopy revealed a decrease in the molecular mass of all resin fractions after catalytic treatment, mainly with a hydrogen donor. However, the elemental analysis data indicated a decrease in the H/C ratio for resin fractions as a result of removing alkyl substituents in resins and asphaltenes. Moreover, the data of 1H NMR spectroscopy of resin fractions indicated an increase in the aliphatic hydrogen index during catalytic aquathermolysis at the high molecular parts of the resins R3 and R4. Finally, a structural group analysis was carried out in this study, and hypothetical structures of the initial oil resin molecules and aquathermolysis products were constructed as well.

Perspective on the Future Approaches to Predict Retention in Liquid Chromatography.

The demand for rapid column screening, computer-assisted method development and method transfer, and unambiguous compound identification by LC/MS analyses has pushed analysts to adopt experimental protocols and software for the accurate prediction of the retention time in liquid chromatography (LC). This Perspective discusses the classical approaches used to predict retention times in LC over the last three decades and proposes future requirements to increase their accuracy. First, inverse methods for retention prediction are essentially applied during screening and gradient method optimization: a minimum number of experiments or design of experiments (DoE) is run to train and calibrate a model (either purely statistical or based on the principles and fundamentals of liquid chromatography) by a mere fitting process. They do not require the accurate knowledge of the true column hold-up volume V0, system dwell volume Vdwell (in gradient elution), and the retention behavior (k versus the content of strong solvent φ, temperature T, pH, and ionic strength I) of the analytes. Their relative accuracy is often excellent below a few percent. Statistical methods are expected to be the most attractive to handle very complex retention behavior such as in mixed-mode chromatography (MMC). Fundamentally correct retention models accounting for the simultaneous impact of φ, I, pH, and T in MMC are needed for method development based on chromatography principles. Second, direct methods for retention prediction are ideally suited for accurate method transfer from one column/system configuration to another: these quality by design (QbD) methods are based on the fundamentals and principles of solid-liquid adsorption and gradient chromatography. No model calibration is necessary; however, they require universal conventions for the accurate determination of true retention factors (for 1 < k < 30) as a function of the experimental variables (φ, T, pH, and I) and of the true column/system parameters (V0, Vdwell, dispersion volume, σ, and relaxation volume, τ, of the programmed gradient profile at the column inlet and gradient distortion at the column outlet). Finally, when the molecular structure of the analytes is either known or assumed, retention prediction has essentially been made on the basis of statistical approaches such as the linear solvation energy relationships (LSERs) and the quantitative structure retention relationships (QSRRs): their ability to accurately predict the retention remains limited within 10-30%. They have been combined with molecular similarity approaches (where the retention model is calibrated with compounds having structures similar to that of the targeted analytes) and artificial intelligence algorithms to further improve their accuracy below 10%. In this Perspective, it is proposed to adopt a more rigorous and fundamental approach by considering the very details of the solid-liquid adsorption process: Monte Carlo (MC) or molecular dynamics (MD) simulations are promising tools to explain and interpret retention data that are too complex to be described by either empirical or statistical retention models.

Characterization of copolymers of polycarbonate and polydimethylsiloxane by 2D chromatographic separation, MALDI-TOF mass spectrometry, and FTIR spectroscopy

The structure and composition of polycarbonate polydimethylsiloxane copolymer (PC-co-PDMS) was investigated by applying various analytical approaches including chromatographic separation methods, spectrometric, and spectroscopic detection techniques. In particular, size exclusion chromatography (SEC) and liquid adsorption chromatography operating at different conditions (e.g. using gradient solvent systems) were used to achieve separations according to molar mass and functionality distribution. The coupling of both techniques resulted in fingerprint two-dimensional plots, which could be used to easily compare different copolymer batches. Matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry was applied for structural investigations. The different ionization behavior of both comonomers, however, strongly limited the applicability of this technique. In contrast to that, Fourier-transform Infrared (FTIR) spectroscopy could be used to quantify the amount of PDMS in the copolymer at different points in the chromatogram. The resulting methodology was capable of distinguishing PC-co-PDMS copolymer from PC homopolymer chains present in the material.

Charge-based separation of synthetic macromolecules by non-aqueous ion exchange chromatography

Traditional polymer-separation methods, such as size-exclusion chromatography and (gradient) liquid adsorption chromatography, cannot provide separations exclusively based on the number of deprotonated carboxylic-acid groups along the backbone chain of polymers. A novel separation method, based on non-aqueous ion-exchange chromatography (NAIEX), was developed, which allows such a separation of acid-functional polymers that are soluble in organic solvents. The polar, aprotic N-methyl-2-pyrrolidone was found to be a suitable solvent. It features a high relative permittivity (favouring dissociation of ion pairs into free ions) and it is a good solvent for polymers and organic salts, such as triethyl-ammonium formate. A negative charge is established on these polymers by deprotonation of the carboxylic-acid groups in the presence of an organic superbase (tetramethyl guanidine). Traditional potent organic bases, such as triethylamine, do not possess the base strength to compensate for the increase in pKa of polymeric carboxylic acid groups in non-aqueous conditions. Triethyl-ammonium formate is proposed as an alternative to traditional salts used for elution in aqueous ion-exchange chromatography. Separation was performed on an industry-standard strong-anion-exchange column and (near-)universal detection of the polymers was performed by high-temperature evaporative-light-scattering detection. The NAIEX method yielded a separation based on the acid-functionality distribution of the polymer. NAIEX was compared with traditional normal- and reversed-phase liquid-chromatography approaches for the separation of acid-functional copolymers.

Fractionation of Aschalcha extra heavy oil resins and studying their structure

In this paper we isolated resins from a sample of extra heavy oil and from the products of catalytic aquathermolysis in the presence of a cobalt based catalyst and studied their structure. In fact, an oil fraction and 4 resin fractions (R1-R4) have been extracted by liquid adsorption chromatography method in the presence of pure solvents and their binary mixtures in various ratios. Adding the catalyst to the system during heat and steam exposure for 6 hours leads to a significant improvement of the structural-group composition. Thus, the aliphaticity index of R3 decreased as a result of the detachment of alkyl substituents in aromatic fragments under the influence of catalyst and passes into lighter fractions of resins, as well as towards saturated and aromatic hydrocarbons. From another hand, the oxidation coefficient also manifests itself in fractions R1 and R2 as a result of oxidative catalytic cracking processes, which also indicates a redistribution of the group composition. MALDI data have showed that the average molecular weight of resins for each of the fractions has decreased whereas IR spectroscopy has highlighted a change in their structural group composition.