Mixture Components Research Articles

Integrating molecular dynamics simulations and experimental data for azeotrope predictions in binary mixtures.

An azeotrope is a constant boiling point mixture, and its behavior is important for fluid separation processes. Predicting azeotropes from atomistic simulations is difficult due to the complexities and convergence problems of Monte Carlo and free-energy perturbation techniques. Here, we present a methodology for predicting the azeotropes of binary mixtures, which computes the compositional dependence of chemical potentials from molecular dynamics simulations using the S0 method and employs experimental boiling point and vaporization enthalpy data. Using this methodology, we reproduce the azeotropes, or lack thereof, in five case studies, including ethanol/water, ethanol/isooctane, methanol/water, hydrazine/water, and acetone/chloroform mixtures. We find that it is crucial to use the experimental boiling point and vaporization enthalpy for reliable azeotrope predictions, as empirical force fields are not accurate enough for these quantities. Finally, we use regular solution models to rationalize the azeotropes and reveal that they tend to form when the mixture components have similar boiling points and strong interactions.

Composite hemangioendothelioma of breast: A case report with review of literature

Composite hemangioendothelioma (CHE) is an intermediate grade neoplastic tumor of vascular origin. It consists of a varied mixture of benign, intermediate and malignantvascular components. Only few cases of CHE occurring in different soft tissue areas of the body and rarely in internal organs have been reported in literature till now. We report a case of CHE presenting as lump in the breast in a 42 year old female. A review of literature is also presented to create awareness of this entity which can be misleading in breast where angiosarcoma is also known to occur.

Associations of serum persistent organic pollutant concentrations with incident diabetes in midlife women: The Study of Women’s Health Across the Nation Multi-Pollutant Study

BackgroundOrganochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs) that can negatively impact metabolic health through pathways including endocrine disruption. Few studies have evaluated diabetes risk associated with PBDEs. Little is known about the joint effect of exposure to POP mixtures on diabetes risk. ObjectivesWe investigated the relationship between POPs, individually and as mixtures, and diabetes development over 18 years (1999–2016) in midlife women. MethodsWe measured lipid-standardized serum concentrations of 34 PCBs, 19 OCPs, and 14 PBDEs in 1040 midlife women aged 45–56 years from the Study of Women’s Health Across the Nation. We tested the association between POPs measured in 1999/2000 and incident diabetes using Cox proportional hazards models. We evaluated diabetes risk associated with the overall POP mixture using Quantile-Based G-Computation (QBGC). ResultsFor most mixture components, single pollutant and mixtures analyses indicated null associations with diabetes risk, however results were inconsistent. After adjustment, hazard ratios (HRs) of developing diabetes (95% CI) associated with upper exposure tertiles (T2/T3) compared with the first tertile (T1), were 1.7 (1.0, 2.8) at T2 and 1.5 (0.84, 2.7) at T3 for hexachlorobenzene and 1.9 (1.1, 3.3) at T2 and 1.6 (0.88, 2.9) at T3 for PCB 123. A doubling of PBDE 47 was associated with 1.11 (1.00, 1.24) times the risk of T2D. QBGC identified no association for the overall joint effect of the POP mixture on diabetes (HR = 1.04 [0.53, 2.07]). ConclusionExposure to a mixture of PCBs, OCPs, and PBDEs was not associated with incident diabetes in midlife U.S. women, although some individual POPs demonstrated significant yet inconsistent associations with diabetes. Non-linear and non-monotonic dose-response dynamics deserve further exploration. More research is needed on the diabetogenic effects of PBDEs.

EThcD as a Unique Tool for the Top-Down De Novo Sequencing of Intact Natural Ranid Amphibian Peptides.

De novo sequencing of any novel peptide/protein is a difficult task. Full sequence coverage, isomeric amino acid residues, inter- and intramolecular S-S bonds, and numerous other post-translational modifications make the investigators employ various chemical modifications, providing a variety of specific fragmentation MSn patterns. The chemical processes are time-consuming, and their yields never reach 100%, while the subsequent purification often leads to the loss of minor components of the initial peptide mixture. Here, we present the advantages of the EThcD method that enables establishing the full sequence of natural intact peptides of ranid frogs in de novo top-down mode without any chemical modifications. The method provides complete sequence coverage, including the cyclic disulfide section, and reliable identification of isomeric leucine/isoleucine residues. The proposed approach demonstrated its efficiency in the analysis of peptidomes of ranid frogs from several populations of Rana arvalis, Rana temporaria, and Pelophylax esculentus complexes.

Comparative evaluation of bioavailability of Botulinum toxin A complexed with Tizol (titanium glycerosolvate aquacomplex) versus pure Botulinum toxin A solution for bladder mucosa: an experimental study

Introduction. For the treatment of overactive bladder syndrome (OAB), injection of botulinum toxin A (BoNT-A) has been shown to be effective. However, there is a need for a less invasive method for administering BoNT-A, which could significantly expand the treatment options for OAB.Objective. To assess the impact of tizol on the absorption of BoNT-A by the bladder mucosa and compare it to the individual absorption of BoNT-A.Materials & Methods. Dialysis through the mucous membrane of the сalf bladder was used as an experimental model to study changes in bioavailability of BoNT-A complexed with tisol (BoNT-A + T) and pure BoNT-A solution during in vitro experiment. After dialysis, the BoNT-A concentration in both samples was determined using a spectrophotometer. Dialysis curves were plotted according to the data obtained. Kruvchinsky equilibrium dialysis method was used to determine botulinum toxin A bioavailability. The UV spectrophotometry method was used to determine the concentration of BoNT-A in the acceptor medium by reaction of BoNT-A with Benedict's reagent.Results. It was established that the maximum concentration of BoNT-A diffused into the acceptor medium from the blend of the test substance with tizol after nine hours. The area under the curve for dialysis of BoNT-A + T exceeds the area under the curve of pure BoNT-A by almost 20%, suggesting an improvement in the drug's bioavailability when blended with tizol.Conclusion. Based on our experiment, it was found out that the BoNT-A + T has greater bioavailability than a solution of pure BoNT-A. However, the diffusion rate of the component mixture is sufficiently low.

Physicochemical properties of binary mixtures of cation-fluorinated ionic liquids with their non-fluorinated analogues

This work reports an investigation of the physicochemical properties (density, viscosity, refractive index and thermal stability) of four binary mixtures having a common acetate ([OAc]¯), trifluoromethanesulfonate ([OTf]¯) or bis(trifluoromethylsulfonyl)imide ([NTf2]¯) anion with either cation-fluorinated and non-fluorinated methylimidazolium (MIm) or pyridinium (Py) cations respectively, at various temperatures. The mixing behaviour of the binary mixtures was analysed by 1H and 19F Nuclear magnetic resonance (NMR) spectrometry, and the excess properties of the mixtures were calculated from the physicochemical data. The binary mixtures of fluorinated ionic liquids (FILs) with their non-fluorinated or alkyl-substituted analogues (AILs) showed an increase in density and viscosity but a decrease in refractive index with an increase in mole fraction of the pure FILs. The thermal stability of the AILs was higher than the FILs, however, an increase in the mole fraction of the pure FILs in the binary mixtures made a negligible impact on the thermal stability of the binary mixtures. These binary mixtures were found to deviate from ideal behaviour for the different physicochemical properties tending to vary between the extremes of the pure components. The large differences in properties of FILs compared with their non-fluorinated analogues were shown to be associated with the size of the fluorine atoms in the fluoro-alkyl chain, the tendency of the fluoro-alkyl chain to form aggregates with fluorinated anions, and the hydrogen bond acceptor strength of the anions. The excess properties were fitted to the Redlich-Kister polynomial equation, and no significant deviation was obtained. This study shows that the physicochemical properties of the fluorinated ionic liquids can conveniently be adjusted for specific applications by simply varying the amount of the cation-fluorinated component in binary mixtures.

The Effect of Rapeseed Oil Biopolyols and Cellulose Biofillers on Selected Properties of Viscoelastic Polyurethane Foams.

This paper presents the results of research on polyurethane viscoelastic foams (PUVFs) modified with biomaterials. This investigation looked at the effect of the biomaterials on the foaming processes, as well as the acoustical and selected physical-mechanical properties of the foams. Various types of rapeseed oil biopolyols and microcellulose were used to modify the materials. The analysis of properties covered a reference biopolyol-free sample and materials containing 10 wt.%, 20 wt.%, and 30 wt.% of different types of biopolyols in the mixture of polyol components. The biopolyols differed in terms of functionality and hydroxyl value (OHv). Next, a selected formulation was modified with various microcellulose biofillers in the amount of 0.5-2 wt.%. The PUVFs, with apparent densities of more than 210 kg/m3 and open-cell structures (more than 85% of open cells), showed a slow recovery to their original shape after deformation when the pressure force was removed. They were also characterized by a tensile strength in the range of 156-264 kPa, elongation at break of 310-510%, hardness of 8.1-23.1 kPa, and a high comfort factor of 3.1-7.1. The introduction of biopolyols into the polyurethane system resulted in changes in sound intensity levels of up to 31.45%, while the addition of fillers resulted in changes in sound intensity levels of up to 13.81%.

Compact 3D-Printed Unit for Separation of Simple Gas Mixtures Combined with Chemiresistive Sensors.

Inexpensive chemiresistive sensors are often insufficiently selective as they are sensitive to multiple components of the gas mixture at the same time. One solution would be to insert a device in front of the sensor that separates the measured gas mixture and possibly isolates the unwanted components. This study focused on the fabrication and characterization of a compact unit, which was fabricated by 3D printing, for the separation and detection of simple gas mixtures. The capillary, the basic part of the compact unit, was 4.689 m long and had a diameter of 0.7 mm. The compact unit also contained a mixing chamber on the inlet side and a measuring chamber with a MiCS-6814 sensor on the outlet side. Mixtures of ethanol and water at different concentrations were chosen for characterization. The measured calibration curve was found to have a reliability of R2 = 0.9941. The study further addressed the elements of environmental friendliness of the materials used and their sustainability.

Deconvoluting Substrates, Support, and Temperature Effects on Leaching and Deactivation of Pd Catalysts: An In Situ Study in Flow.

Leaching behavior of three different Pd heterogeneous catalysts (PdEnCat 30, FibreCat FC1001, and Pd/Al2O3) during the Heck reaction of iodobenzene and methyl acrylate, in the presence of triethylamine, was compared using a tandem flow reactor. While leaching was observed in all three cases, Pd/Al2O3 appeared to be the most robust, showing little/no leaching at ambient temperature. The leached Pd species also appear to display different catalytic activities. With a slight modification of the reactor, the leaching caused by individual components of the reaction mixture can be assessed separately. For the polymer-supported catalysts, triethylamine caused the largest amount of leaching, even at 30 °C. In contrast, the leaching from Pd/Al2O3 was observed only in the presence of iodobenzene at 90 °C. Variations in leaching behavior were ascribed to differences in Pd species and immobilization methods.

The Properties of the Physical Parameters in the Triple Diffusive Fluid Flow Model

The existence of more than one diffusive component in fluid mixtures is observed in these situations: underground water flow, the mechanism of acid rain, the existence of contaminant in some certain mixture, etc. These diffusive components are occurred with the single temperature gradient (since all of the elements are dissolved into the same mixture) and 2 types of concentration gradients (since the dual diffusive components are dissolved in the same mixture). Besides, many industrial and engineering processes are utilizing the concept of convective fluid flow especially over a shrinking sheet. Therefore, a mathematical model for triple-diffusive flow over a nonlinear compressing sheet has been developed in this paper, and subjected to the Soret-Dufour effects. The model comprises of five initial equations namely continuity, momentum, energy, concentration of component 1 and concentration of component 2 equations, together with boundary conditions. These initial equations are expressed as partial differential equations. However, the finalized equations are in the form of ordinary differential equations. Later, the bvp4c programme provided by the Matlab Software is used to solve the ordinary differential equations and the boundary conditions. Three distinct values of each governing parameter are fixed into the bvp4c function, to observe the behaviour of the physical parameters, namely as local Nusselt number and local Sherwood number. The main finding of the dual numerical solutions varies for increasing governing parameters until they intersect at the critical points. In conclusion, the governing parameters affects the heat and mass transfer of the fluid flow model model.

Efficacy and safety of subcutaneous immunotherapy with polymerized allergen mixtures in polyallergic patients – ARES observational study

ABSTRACT Background Administration of allergen mixtures of many components comprises the most common approach for American allergists regarding the management of polyallergic patients. European allergists, however, are more reluctant to this type of treatment due to the potential drawbacks of mixing extracts. Research design and methods To assess the efficacy and safety of subcutaneous immunotherapy (SCIT) with polymerized allergen mixtures without dilutional effect in polyallergic patients. This observational, prospective, multicenter study included patients (between 5 and 60 years) with respiratory allergic diseases that had been prescribed with SCIT with mixtures of two pollen or mite extracts. Changes in Symptoms and Medication Score (SMS) and in rhinitis quality of life questionnaire (RQLQ), subjective clinical improvement, treatment satisfaction and tolerability were assessed after the 1-year treatment. Results A total of 115 patients were included in the assessment. Mean global SMS decreased from 3.5 (SD = 1.1) to 1.6 (SD = 1.2) points, with a mean absolute reduction of 1.6 (SD = 1.3) points in the RQLQ score (p < 0.001, Wilcoxon test). General subjective clinical improvements and a good treatment satisfaction and tolerability were observed. Conclusion SCIT with polymerized allergen mixtures from either pollen or mite extracts proved to be an effective and safe treatment option for polyallergic patients suffering from allergic respiratory diseases.

Chemical Composition of Volatile and Extractive Organic Compounds in the Inflorescence Litter of Five Species of Woody Plants.

The decomposition of plant litter, most of which is found in forests, is an important element of the global carbon cycle, as a result of which carbon enters the atmosphere in the form of not only CO2 but also volatile organic compounds (VOCs). Although the formation of litter is associated with autumn cooling, in the spring, there is a very intense fall of faded inflorescences of woody plants. This study examined the chemical composition of the litter and VOCs emitted from decaying inflorescences of four species of forest-forming trees: silver birch, European hornbeam, black alder and aspen. All litter emissions consisted of 291 VOCs, mainly terpenes actively participating in atmospheric processes. The detection of a number of typical mushroom metabolites, such as 1-octen-3-ol, known as "mushroom alcohol", and alkyl sulphides, suggests that inflorescence-derived VOCs are a mixture of components of plant and microbial origin. In methanol extracts of the fallen inflorescences of all types, 263 organic compounds were identified, the majority of which were related to carbohydrates. Their share in the extracts was 72-76%. In general, the composition of the extractive compounds indicates the easy availability of this material for assimilation by various types of destructors.

Leveraging independence in high-dimensional mixed linear regression.

We address the challenge of estimating regression coefficients and selecting relevant predictors in the context of mixed linear regression in high dimensions, where the number of predictors greatly exceeds the sample size. Recent advancements in this field have centered on incorporating sparsity-inducing penalties into the expectation-maximization (EM) algorithm, which seeks to maximize the conditional likelihood of the response given the predictors. However, existing procedures often treat predictors as fixed or overlook their inherent variability. In this paper, we leverage the independence between the predictor and the latent indicator variable of mixtures to facilitate efficient computation and also achieve synergistic variable selection across all mixture components. We establish the non-asymptotic convergence rate of the proposed fast group-penalized EM estimator to the true regression parameters. The effectiveness of our method is demonstrated through extensive simulations and an application to the Cancer Cell Line Encyclopedia dataset for the prediction of anticancer drug sensitivity.

Mix and manage: Cultivar mixtures can maintain yield under high wheat blast disease pressure

Originating in South America, wheat blast disease has spread to both Asia and Africa and is considered a significant threat to food security. Bangladesh experienced the first outbreak of wheat blast outside of the Americas in 2016. Shortly thereafter, the blast-resistant variety BARI Gom 33 was released. Seeds of this variety are however not as widely available as required, although the disease threat remains. While varietal mixtures have been shown to mitigate some symptoms and yield losses associated with other fungal diseases in wheat, there is a complete research gap on this topic as it pertains to wheat blast. As such, we evaluated the potential of using BARI Gom 33 as a component of a variety mixture under high disease pressure in Bangladesh. During three cropping seasons, blast symptoms and yield were determined in a field experiment for the highly blast-susceptible variety BARI Gom 26, the moderately susceptible BARI Gom 30, the resistant BARI Gom 33, and seven mixture combinations of the three varieties using artificial inoculation to increase disease pressure. In addition to wheat blast, Bipolaris leaf blight (BpLB) symptoms were observed and evaluated. While yields of the susceptible varieties were severely affected by blast even after fungicide application, disease-inflicted yield loss without fungicide was only 15% for sole BARI Gom 33 and did not differ significantly from yield losses in BARI Gom 33 and BARI Gom 30 mixtures. Furthermore, in the mixture containing 67% BARI Gom 33 and 33% BARI Gom 30, blast incidence and severity were reduced by 25% and 16%, respectively, in comparison to weighted values in sole stands. Conversely, mixing varieties tended to increase the symptoms of BpLB. Under high wheat blast pressure, fungicide protection against blast was relatively weak, underscoring the importance of resistant varieties. Although variety mixtures did not increase yield, the yield advantage of BARI Gom 33 was maintained when its seeds were mixed with the less resistant BARI Gom 30. This study confirms recommendations that farmers should use BARI Gom 33 as a first line of defense against wheat blast in Bangladesh. Yet where farmers cannot access sufficient BARI Gom 33 seed for planting, our data suggest that agricultural extension services can recommend this variety with non-resistant cultivars as interim strategy without significant risk of yield loss.

Modification of pea starch using ternary mixtures of natural crosslinking agents: Vanillin-chitosan-betaine and vanillin-gelatin-betaine

Different methods of starch modification have been proposed to broaden its application. In this study, the effects of ternary mixtures of natural crosslinking agents: chitosan-betaine-vanillin and gelatin-betaine-vanillin on the properties of pea starch were explored. These combinations of substances were selected because they have complementary crosslinking mechanisms. The effects of the ternary crosslinker mixtures on the gelatinization, mechanical properties, thermal stability, and microstructure of pea starch were compared. Both combinations of crosslinkers enhanced the gelatinization viscosity, viscoelasticity, gel hardness, and thermal stability of the pea starch, by an amount that depended on the ratio of the different components in the ternary mixtures. In all cases, the crystal structure of the starch granules disappeared after gelatinization. The modified starch had a more compact and uniform microstructure than the non-modified version, especially when it was crosslinked by vanillin, gelatin, and betaine. The improvement in the gelation properties of the starch were primarily attributed to hydrogen bonding, electrostatic attraction, and Schiff base crosslinking of the various components present. Gelatin enhanced the gel strength more than chitosan, which was probably because of greater hydrogen bonding. Our findings suggest that the properties of starch can be enhanced by adding ternary mixtures of natural crosslinkers.

Mobility-induced kinetic effects in multicomponent mixtures

We give an overview exploring the role of kinetics in multicomponent mixtures. Compared to the most commonly studied binary (single species plus solvent) case, multicomponent fluids show a rich interplay between kinetics and thermodynamics due to the possibility of fractionation, interdiffusion of mixture components and collective motion. This leads to a competition between multiple timescales that change depending on the underlying kinetics. At high densities, crowding effects are relevant and non-equilibrium structures can become long-lived. We present the main approaches for the study of kinetic effects in multicomponents mixtures, including the role of crowding, and explore their consequences for equilibrium and non-equilibrium scenarios. We conclude by identifying the main challenges in the field.

Goodness-of-fit, identifiability and extrapolation: Can the Two-Component Extreme Value distribution be used in at-site flood frequency analysis?

When fitting three-parameter flood frequency models to annual maximum (AM) flood series, the lack-of-fit can be mitigated by censoring potentially influential low flows (PILFs). An alternative and less-studied approach is to apply mixture probability models with four or more parameters, which trade off greater flexibility to fit AM series against the need to deal with degeneracy which arises when there is insufficient information to identify mixture components. However, the issue of degeneracy and the lack of a robust inference framework present a significant barrier to adoption. This study investigated the potential of the most parsimonious mixture model, the four-parameter Two-Component Extreme Value (TCEV) model. A Bayesian framework using Markov chain Monte Carlo sampling was developed to robustly characterize parameter uncertainty even in the presence of degeneracy. Two new posterior diagnostics based on the strength of the TCEV components were developed to aid identification of degeneracy. Armed with a robust inference framework, the study evaluated the potential of TCEV using a case study based on 31 catchments in eastern Australia with records exceeding 70 years. The evaluation used short to long records to compare TCEV and Log Pearson III fit and extrapolative uncertainty. The Log Pearson approach (LP3-PILF) censors PILFs following the approach described in Australian Rainfall and Runoff. With respect to goodness-of-fit, we found in most cases that TCEV fitted AM flood peaks well without the need to censor or stratify data, and overall, no clear difference emerged between TCEV and LP3-PILF. However, and contrary to expectation, TCEV produced high flow quantile confidence intervals consistently narrower than LP3-PILF even in the presence of degeneracy. While more case studies in different regions are needed to confirm the potential of TCEV, this study is a reminder that goodness-of-fit is a necessary but not sufficient criterion for selecting the probability model that best represents flood frequency.

DEVELOPMENT OF AN ALGORITHM FOR CALCULATING COMPONENT COMPOSITION TO IMPROVE THE DEVELOPMENT OF OFFSHORE OIL FIELDS IN THE NORTH CASPIAN BASIN

The paper presents an algorithm to reconstruct the component composition of the mixture based on the results of production modeling in the black oil format and a fixed set of tables with the results of phase equilibrium calculations in a given pressure range. The approach is based on analyzing the ratio of flow rates for each phase and the ratio between average reservoir pressure and saturation pressure. The algorithm takes into account the possibility of oil degassing when saturation pressure decreases, as well as gas breakthrough of gas caps to the bottoms of producing wells.Implementation of the method is based on a unified thermodynamic model of multilayer reservoir, built on the principles of a single set of HC mixture components and uniform parameters of the equation of state on a set of fluid samples for all modeling stages: reservoir model, model of the gathering system and site facilities. In addition to steady-state flow calculations performed together with reservoir modeling, the unified model is planned to be used for dynamic flow calculations in the corresponding simulator (well start/stop), which will allow solving production problems in the process of operation of wells with complex completions.The conversion algorithm is automated using modern high-level tools: Python and data automation components from MS Excel, which eliminates the need for manual data input at all stages and makes it possible to obtain the estimated component composition of produced fluid for any set of wells and for any time step within the forecasting horizon.The obtained compositions are used to verify the reproduction of the main controlled parameters (oil density and gas oil ratio) and can be used for subsequent calculations of fluid transportation and treatment systems.The implemented algorithm has been tested for stability at different ratios of gas and oil flow rates by wells and meets the practical requirements of engineering calculations — the error of oil density is not higher than 2 % and gas factor is not higher than 10 %.

Сорго – альтернативная зерновая культура в мясном птицеводстве

Realization of the genetic potential of farm animals and poultry is possible only with the use of complete diets. Along with the traditional plant components of feed, alternative agricultural crops that are capable of high yields in adverse environmental conditions, such as drought and salinity, are of great help in forage production and at the same time have a high nutritional value. The article presents the results of studies on the use of grain sorghum as a component of combined feed for broiler chickens in the conditions of the Saratov region. In experimental feeds, sorghum was replaced by cereals ‒ barley and wheat, which are traditional components for feed mixtures. After a preliminary study of the biochemical composition of the feed components, prototype feed samples were compiled, in which the nutritional value was determined by the main indicators - protein, fat, fiber, ash, BEV, the exchange energy was calculated and the fractional composition of the protein was studied - albumins, globulins, glutelins, prolamins. After analyzing the combination of all indicators of the feed value of the studied compound feeds, sample N 3 was selected, in which grain sorghum was used instead of barley, with optimal characteristics, and recommended for further use. Keywords: SORGHUM, COMPOUND FEED, BROILER CHICKENS, METABOLIC ENERGY, FEED VALUE, PROTEIN, PROTEIN FRACTIONS

OPTIMIZATION OF THE OPERATION OF AN ISOMERIZATION INSTALLATION FOR LIGHT PETROL FRACTIONS

The interest in this process lies in the fact that it has great value since low-octane components are used as raw materials - the n fraction. temperature – 62°С and catalytic reforming raffinates. This raw material contains mainly pentane and hexane fractions. This raw material, as well as fractions С5 and С6 obtained from a gas fractionation unit (GFU), and a central gas fractionation unit (CGFU), are isomerized in a hydrogen environment in the presence of a catalyst. Hydrocarbons with a relatively high octane number are obtained. When isomerizing the pentane fraction, a product with a higher octane number is obtained. Isomerization of n-pentane is of interest not only for the oil refining industry, but also for the petrochemical industry, since isopentane can be converted by dehydrogenation into isoprene, a raw material for rubber. The article conducted a study on the selection of the optimal catalyst for the light gasoline fraction isomerization unit located at the Atyrau Oil Refinery. The catalytic activity of the catalyst samples was assessed in a laboratory flow-type installation. Determination of the mass fraction of С2-С5 hydrocarbons in С5 hydrocarbon fractions (in raw materials and catalyst) was carried out by a method based on the separation of mixture components by gas-liquid chromatography. The components leaving the chromatographic column were detected using a thermal conductivity detector. The calculation of the mass fractions of components was carried out using the normalization method, taking into account correction factors. The minimum concentration of C2-С5 hydrocarbons, determined by the method used, is 0.01-0.05% wt.