Model Mixture Research Articles

Spectrometric Determination of the Total Concentration of Single-Type Analytes Using Conventional Multidimensional Calibrations

Multidimensional calibrations can be used for the spectrometric determination of the total concentration (cΣ) of similar substances; these calibrations relate the generalized signals (AΣ)j measured at different wavelengths (λj) with the concentrations of these analytes (ci) and their absorption coefficients (kij). Such calibrations are conventionally used for the separate determination of analytes, while the ci values are calculated using chemometric algorithms. To find cΣ, one should only take a sum of the found ci values. Despite the simplicity of this type of group analysis, it is rarely used, and its capabilities have not been studied. It is unclear how the accuracy of the cΣ estimate depends on the number of analytical wavelengths (AWLs), the number of standards, and other factors. The purpose of this study was to obtain relevant information using an example of model mixtures of arenes. The absorption spectra of arene mixtures were recorded in the region 230–280 nm, where these spectra are additive. We analyzed 55 hexane solutions containing three to six arenes with a total concentration of 0.1–0.5 mg/mL. The qualitative composition of the model mixtures was considered to compose the matrix of absorption coefficients of individual arenes. The ci values were found by multiple linear regression (MLR, direct calibration). With a sufficiently large number of AWLs, the found ci values were close to zero for arenes absent in the sample and close to the actual ci values for the present arenes. The summation of the found ci gave approximately correct estimates of cΣ (±5%). The single errors of the group analysis were, as a rule, smaller than the errors of the determination of the mixture components. The complication of the model (the introduction of “extra” standards and an increase in the number of AWLs) did not affect the accuracy of the results of group analysis, and the simplification of the model increased errors. If only the most typical standards were used to form the model, the values of kij of which covered the entire range of possible values of kij, the presence of components in the sample that were not taken into account by the simplified model did not lead to a noticeable increase in errors.

Advanced separation strategies for up-gradation of bio-oil into value-added chemicals: A comprehensive review

This work gives an outline of current research patterns in bio-oil separation techniques and their applications. Due to unpredictable nature of bio-oil, various challenges have been reported in downstream operations. Several methods have been presented to redesign the bio-oil by separating the combination of bio-oil compounds into a group of chemical substances and portions advanced in definite groups of chemical mixtures. In this review, different separation strategies for bio-oil such as fractionation, water extraction, organic solvent extraction, supercritical fluid extraction, and membrane separation, with the qualities of bio-oil extracts and their applications have been discussed. It was found that the most favorable techniques are fractionation and organic solvent extraction. The present review focuses on recent developments made from model mixtures present in bio-oil as well as pyrolysis bio-oil; techno-economical analysis has been presented for researchers who are expected to bridge knowledge gap and for industrial practitioners.

Investigation of the relative reactivity of aromatic compounds in air under the action of pulsed discharge plasma

Based on the method of competing reactions, a method for determining the relative reactivity of aromatic vapors in relation to the plasma components of a pulsed corona discharge is developed. The parameters of the relative reactivity of aromatic compounds in the air and nitrogen stream were obtained using model mixtures based on benzene, toluene, and xylene with a content of 250-500 ppm. The effect of water vapor on the process is shown. The obtained data will be useful for optimizing the processes of plasma-chemical air purification from the vapors of toxic aromatic compounds. Keywords: Corona discharge, aromatic compounds, non-equilibrium atmospheric pressure plasma, air purification, volatile organic compounds, BTEX.

Elaboration and characterization of polymers used in flexible multilayer food packaging

Mechanical recycling is a major alternative for reducing the amount of fossil and natural resources needed to produce plastic materials. The process is essential when it comes to recycling multilayer plastic parts such as flexible food packaging. However, this recycling method generates a multiphase material whose interfaces must be stabilized so that it can be recovered. The nature of polymeric materials as well as their composition in flexible food packaging allows to achieve this, only if a chemical reaction is developed during the mixing stage (in-situ reaction). This work was the opportunity to demonstrate the potential of this strategy from model mixtures consisting of Linear Low Density Polyethylene (LLDPE)/ Ethylene Vinyl Alcohol copolymer (EVOH) and a commercial tie polymer called OREVAC. The latter is a linear low-density polyethylene-graft-maleic anhydride. In this work, two types of OREVAC were used (OR-PE 1 and OR-PE 2) as compatibilizers. The rheological and morphological results show the effect of the added compatibilizer, and the limited efficiency obtained due to the low quantity which has been used in the blends.

Immobilization of phosphonium-based ionic liquid stationary phases extends their operative range to routine applications in the flavor, fragrance and natural product fields

Phosphonium-based ionic liquids (ILs) have proven to be successful stationary phases (SPs) for gas chromatography (GC) in several fields of application because of their unique selectivity and good chromatographic properties. This study focuses on the use of two ILs as GC SPs that are based on the phosphonium derivatives trihexyl(tetradecyl)phosphonium chloride ([P66614+] [Cl−]), and trihexyl(tetradecyl)phosphonium bis[(trifluoromethyl)sulfonyl]imide ([P66614+][NTf2−]), which have previously been shown to be complementary in terms of chromatographic selectivity and retention. Their application in routine analysis has been limited by their lower maximum allowable operating temperatures (MAOT) (200 °C for the [P66614+][Cl−] IL and 180 °C for [P66614+][NTf2−]), which restricts their use to samples that consist of analytes with relatively high volatility. A previous study carried out in the Authors’ laboratory focused on extending the use of the [P66614+][Cl−] IL SP to the analysis of samples with analytes of medium-to-low volatility by optimizing column characteristics and operative conditions. This study addresses the immobilization of both the [P66614+][Cl−] and [P66614+][NTf2−] ILs to the inner wall of fused silica columns to increase their MAOT under soft and hard reaction conditions. The resulting MAOT depended on more or less drastic immobilization conditions, and reached 220 °C for soft immobilization (So-Im) and 240 °C for hard immobilization (Ha-Im) in the [P66614+][Cl−] IL columns, and 200 °C for So-Im and 220° for Ha-Im in columns coated with the [P66614+] [NTf2−] IL. The influence of immobilization on the separation power and performance of all the columns has been evaluated using i) the Grob test, ii) a model mixture of 41 compounds of different polarity, structure, and with different organic functional groups representative of the flavor and fragrance field, iii) a standard mixture of 37 fatty acid methyl esters, iv) the peppermint essential oil, v) two mixtures of sesquiterpenic alcohols (farnesols and santalols), and vi) a standard mixture of 16 pesticides. These test samples were also used to demonstrate the complementarity of the two phosphonium-based IL SPs in terms of selectivity and retention.

Comparison of the efficiency of square cascades with an additional product flow and double cascades to concentrate intermediate isotopes

Original techniques were proposed for calculating and optimizing double cascades (DC) built of square cascades and a square cascade with an additional product flow (SCAP). Both cascade schemes (DC and SCAP) were tested in solving a task of simultaneous enrichment of three components of a model mixture to a pre-defined level. A comparison of the DC and SCAP efficiency was made according to the minimum of total cascade flow. The results have shown that the double cascade is more efficient in terms of the chosen criterion.

Влияние концентрата пищевых волокон из яблок на хлебопекарные свойства мучных смесей

Enriched bakery projection requires an integrated approach to satisfy consumers, both in the sensory characteristics of the product and in its composition. When implementing this approach, it is advisable to research the influence of enriching ingredients on the baking properties of flour mixtures, in which these ingredients are introduced. As an enriching ingredient was selected dried and milled husks from apple juice of direct spinning, which relates to semi-concentrated alimentary fiber. The results of studying the behavior of model mixtures of wheat flour and concentrated apple alimentary fiber, carried out on Brabender devices – amylograph and farinograph – showed a significant change in baking properties. With an increase in the dosage of the semi-concentrated alimentary fiber in the mixture till 15 %, the dough formation time and its viscosity increase, the stability and complex quality characteristics according to the farinogram decrease, thinning grows. The established patterns can be due to the moisture redistribution in dough because of high water-absorbing and water-retaining ability of alimentary fiber. Established patterns should be taken into account when choosing the type of enriched product, the dosage of the enriched ingredient and technology parameters of enriched bakery.

The Process of Separating Buckwheat and Wheat Grain in a Pneumatic Cone Separator in the Context of Sustainable Agriculture

In machines and devices used for separating and cleaning seed mixtures, the components of such mixtures can be separated in a stream of air. The efficiency of separation of a two-component (model) mixture containing wheat kernels and buckwheat nutlets was investigated. The main crop seeds and other crop seeds imitating impurities accounted for 80% and 20% (w/w), respectively. The experiment involved a pneumatic cleaning device with an immobile conical surface, designed by the authors, where mixture components are separated in a stream of air. The seed mixture was separated in a separator with the shape of an inverted cone, where the seeds were set into motion by a stream of air. The separation efficiency of the analyzed two-component mixture in the designed separator exceeded 78%. Regression equations describing the separation efficiency index of the entire seed mixture (ε) and the separation efficiency of the main crop seeds (ηp) and seeds imitating impurities (ηz) were derived. The coefficient of determination (R2) for the above regression equations describing the separation efficiency of the mixture components (main crop seeds and seeds imitating impurities) and the separation efficiency index of the entire seed mixture ranged from 0.81 to 0.94. This result indicates that the developed equations were characterized by satisfactory and highly satisfactory fit to empirical data, and that they can be applied to accurately predict the quality of the seed separation process in the cleaning device designed by the authors. The developed equations can be effectively used to model and automatically control separation processes in the proposed separator.

Novel Mixed Matrix Membranes Based on Polymer of Intrinsic Microporosity PIM-1 Modified with Metal-Organic Frameworks for Removal of Heavy Metal Ions and Food Dyes by Nanofiltration

Nowadays, nanofiltration is widely used for water treatment due to its advantages, such as energy-saving, sustainability, high efficiency, and compact equipment. In the present work, novel nanofiltration membranes based on the polymer of intrinsic microporosity PIM-1 modified by metal-organic frameworks (MOFs)—MIL-140A and MIL-125—were developed to increase nanofiltration efficiency for the removal of heavy metal ions and dyes. The structural and physicochemical properties of the developed PIM-1 and PIM-1/MOFs membranes were studied by the spectroscopic technique (FTIR), microscopic methods (SEM and AFM), and contact angle measurement. Transport properties of the developed PIM-1 and PIM-1/MOFs membranes were evaluated in the nanofiltration of the model and real mixtures containing food dyes and heavy metal ions. It was found that the introduction of MOFs (MIL-140A and MIL-125) led to an increase in membrane permeability. It was demonstrated that the membranes could be used to remove and concentrate the food dyes and heavy metal ions from model and real mixtures.

Kinetic aspects of bromination of a phthalate-type plasticizer

The main characteristics of a complex system of unsaturated plasticizer-bromine using the main "working components" - isomers of 2-ethylhexyl-2-ethylhexene phthalate are considered. It is taken into account that the phthalate-type ester plasticizer is a polar compound with a dipole moment at the level of dioctyl phthalate included in its composition. It has been shown that in the process of bromination, molecular bromine enters into physical interaction with all components of the plasticizer. Dosed introduction of bromine into the system at high stirring speeds leads to the formation of a homogeneous thermodynamically stable system, since the solubility parameters of the components are practically the same. Using a model mixture of bromine-dioctyl phthalate-dibutyl phthalate, it was shown that mixing bromine with plasticizers in any investigated ratios does not lead to the appearance of the boundary “bromine in a plasticizer” or “plasticizer in bromine”. This established the unlimited solubility of bromine in the plasticizer under the conditions of its bromination. Using the method of UV spectroscopy on model mixtures of acetic acid-bromine-water; acetic acid-bromine-hexane, it was proved that in a real system, unsaturated plasticizer-bromine, bromination is most likely carried out only with molecular bromine without the formation of bromine dimers. The mechanism of bromination of unsaturated phthalates included in the plasticizer is shown. A system of kinetic equations in dimensionless variables is proposed. It was found that the nature of the theoretical curves significantly depends on the rate of introduction of bromine with a constant reaction mechanism. A change in the limiting stages of the bromination process was noted depending on the rate of bromine introduction into the system.

Validation of the infrared spectroscopy method for analysis of the composition of urine concretes.

The aim of this study was to validate the method for analyzing the composition of calculus using infrared (IR) spectroscopy by studying model mixtures of salts. Study was made with an ALPHA-P IR Fourier spectrometer with OPUS software (Bruker, Germany). The samples of pure chemical salts manufactured by Sigma-Aldrich USA were used to validate the method. Salt mixtures were prepared in ratios of 10/90, 50/50 and 90/10. To assess the effect of the fraction size on the calculus component results, were used calculi of patients with urolithiasis. For each mixture were used 10 repeated measurements. Analysis of the composition of model salts showed that in the study of pure cystine salt CV(%) was 0,79%, calcium carbonate - 0,92%, sodium urate - 0,97%, calcium oxalate monohydrate - 4,94%, magnesium ammonium phosphate - 5,59%. And the most common components were analyzed in the composition of complex mixtures, including 90%, 50% and 10% of the investigated component. Calcium oxalate monohydrate has CV(%) 5.70% in mixture 9 part of it to one part of impurities, in mixture 50/50 - 21.57% and in 10/90 - 5.70%. For uric acid in 90/10 - 2.20%, in 50/50 - 10.09%, in 10/90 - 31.94%. For calcium carbonate in 90/10 - 9.02%, in 50/50 - 11.98%, in 10/90 - 24.70%. The dispersion analysis showed that the weighed portions of salts with a particle diameter of more than 0.8 mm provide reproducibility with a CV - 11.48%, with a diameter of 0.2-0.8 mm - 5.35%, and finally less than 0.1 mm - 2.28%. The accuracy of the method is high, but the reproducibility of the IR-spectroscopy method is relatively low in the analysis of stones of mixed composition, due to the greater error in the determination of impurities. Laboratories should pay special attention to optimizing sample preparation to ensure particle fineness less than 0.1 mm.

Combining an Integrated Sensor Array with Machine Learning for the Simultaneous Quantification of Multiple Cations in Aqueous Mixtures.

The direct quantification of multiple ions in aqueous mixtures is achieved by combining an automated machine learning pipeline with transient potentiometric data obtained from a single miniaturized array of polymeric sensors electrodeposited on a conventional printed circuit board (PCB) substrate. A proof-of-concept system was demonstrated by employing 16 polymeric sensors in combination with features extracted from the transient differential voltages produced by these sensors when transitioning from a reference solution to a test solution, thereby obviating the need for a conventional reference electrode. A tree-based regression model enabled concentrations of various metal cations in pure solutions to be determined in less than 2 min. In a model mixture comprising Al3+, Cu2+, Na+, and Fe3+, the mean relative error was found to depend on the type of ion and varied between 1% for Fe3+ and 44% for Na+ in the concentration range 1-10 mg/L. Overall, a mean relative error of 16% was obtained for quantification of these four ions across a total of 124 tests in different solutions spanning concentrations between 2 and 360 mg/L. These results demonstrate how the analytical capability of a multiselective sensor array can leverage data-driven approaches through training by examples for accelerated testing and can be proposed to complement traditional analytical tools to meet industrial demands, including traceability of chemicals.

Development and validation of TaqMan real-time PCR assays for quantification of chicken adulteration in hamburgers

Four quantification methods based on absolute (model Ⅰ), relative (model Ⅱ) and normalized approaches (models Ⅲ and Ⅳ) were developed to estimate the percentage of chicken substitution in beef burgers using TaqMan real-time PCR. The cytochrome b (cytb) and 18S ribosomal RNA (18S rRNA) regions were used for the chicken identification and normalization of assay results, respectively. The plotted curves of four models using the reference chicken-beef mixtures represented the linear correlation (0.9962−0.9995), and the acceptable amplification efficiencies (98.60 %–110.12 %) within the range of recommended values. The results of validation plan using the model samples (mixtures and burgers prepared with chicken meat or chicken paste in beef meat) showed the better trueness parameters for model mixtures in models Ⅲ and Ⅳ (−0.12 % to −18.03 %) in comparison with models Ⅰ and Ⅱ (−5.11 % to −43.95 %). Also, an over-estimation of chicken adulteration in model burgers was quantified by models Ⅰ and Ⅱ (with trueness 99.18 %–170.19 %), while the normalized models gave a more accurate estimation of chicken percentage (with trueness −0.26 % to −1.29 %). The developed TaqMan-qPCR assay could reliably quantify 0.01 % of chicken meat in chicken-beef mixtures without any cross-reactivity. Finally, the normalized approaches as validated models recognized the mislabeling in some commercial hamburger brands.

Molecularly imprinted polymer as a synthetic antibody for the biorecognition of hazelnut Cor a 14-allergen

Artificial receptors that mimic their natural biological counterparts have several advantages, such as lower production costs and increased shelf-life stability/versatility, while overcoming the ethical issues related to raising antibodies in animals. In this work, the proposed tailor-made molecularly imprinted polymer (MIP)-allergen receptors aimed at substituting or even transcending the performance of biological antibodies. For this purpose, a MIP was proposed as an artificial antibody for the recognition of hazelnut Cor a 14-allergen. The target protein was grafted onto the conducting polypyrrole receptor film using gold screen-printed electrodes (Au-SPE). The electrochemical assessment presented a linear response for the dynamic range of 100 fg mL−1-1 μg mL−1 and a LOD of 24.5 fg mL−1, as determined by square wave voltammetry from the calibration curves prepared with standards diluted in phosphate buffer. Surface plasmon resonance (SPR) was used as a secondary transducer to evaluate the performance of the Cor a 14-MIP sensor, enabling a linear dynamic range of 100 fg mL−1- 0.1 μg mL−1 and a LOD of 18.1 fg mL−1. The selectivity of the tailored-made Cor a 14-MIP was tested against potentially cross-reactive plant/animal species based on the rebinding affinity (Freundlich isotherm-KF) of homologues/similar proteins, being further compared with custom-made polyclonal anti-Cor a 14 IgG immunosensor. Results evidenced that the MIP mimics the biorecognition of biological antibodies, presenting higher selectivity (only minor cross-reactivity towards walnut and Brazil nut 2S albumins) than the Cor a 14/anti-Cor a 14 IgG immunosensor. The application of electrochemical Cor a 14-MIP sensor to model mixtures of hazelnut in pasta enabled quantifying hazelnut down to 1 mg kg−1 (corresponding to 0.16 mg kg−1 of hazelnut protein in the matrix). To the best of our knowledge, Cor a 14-MIP is the first sensor based on an artificial/synthetic biorecognition platform for the specific detection of hazelnut allergens, while presenting high-performance parameters with demonstrated application in food safety management.

Life satisfaction among individuals with opioid use disorder receiving extended-release naltrexone: A 12-week randomized controlled trial and a 36-week follow-up

IntroductionLife satisfaction (LS) in opioid-dependent individuals is lower than in the general population. This study aimed to explore changes in LS during short- and long-term treatment with extended-release naltrexone (XR-NTX). MethodsThis open-label 12-week clinical trial randomized 159 participants to either monthly XR-NTX or daily buprenorphine-naloxone (BP-NLX). In a subsequent 36-week follow-up study on XR-NTX, participants either continued or switched to XR-NTX. The study collected data on the Temporary Satisfaction with Life (TSWL) and illicit opioid use every fourth week. The research team assessed changes in TSWL by a linear mixed model and growth mixture model. The study assessed relationship between opioid use and TSWL by a linear mixed model. ResultsChange in LS differed significantly between the groups in both study periods. TSWL scores were significantly higher in the XR-NTX group at week 4 (p = 0.013) and week 8 (p = 0.002). In the follow-up period, the groups were significantly different only at week 16 (p = 0.031) and week 48 (p = 0.025), with the higher TSWL scores in the XR-NTX continued group. Increase in opioid use by one day was associated with a 0.12 point lower mean TSWL score. Both study periods identified groups with low and high LS levels. In the trial period, the TSWL scores exhibited a significant increase from baseline to week 12 in both groups, p < 0.001 and p = 0.011 in the low and high LS group, respectively. In the follow-up period, the TSWL scores exhibited a significant increase from week 16 to week 48 (p = 0.003) in the high LS group, while the low LS group showed persistently lower values throughout that period. ConclusionsXR-NTX treatment given once monthly is associated with higher LS, as measured by TSWL, compared to daily use of BP-NLX. The majority of the participants had relatively low TSWL scores and did not report any change in TSWL during longer-term treatment. The study found a significant association between more frequent illicit opioid use and a low or decreased LS during follow-up.

Effect of protective bed composition on deactivation of a hydrotreating catalyst

AbstractBACKGROUNDThe relationship between the chemical composition, texture, and the shape of the granules of the protective bed upstream hydrotreating, that influences the degree of metal removal from the residual vacuum gas oil, is a critical issue in oil refining.RESULTSThe character of the metal and sulphur distribution on the surface and in the volume of granules of the protective beds was studied for the model mixtures enriched with typical compounds deactivating hydrodesulphurization catalysts. The protective bed was operated along with the demetallization catalyst synthesized using local mineral raw materials (e.g., Angren high‐quality enriched kaolin) and production wastes (spent alumina sorbent from Shurtan gas chemical complex).CONCLUSIONIt is shown, the use of a two‐bed protective system most effectively extended the life‐time of the main hydrotreating catalyst. The spent and deactivated Al‐Co‐Mo catalyst can be efficiently used in the synthesis of the catalyst used for the pre‐cleaning upstream hydrotreating. © 2021 Society of Chemical Industry (SCI).

Effect of Individual Sulfide on the Stability against Oxidation of Transformer Oil and Its Electrical Parameters

This study is devoted to the improvement of the transformer oil quality, using a new inhibiting additive, since the extensively used inhibitory additive ionol is sensitive to organosulfur compounds of sulfur oils. From the earlier works, the organosulfur compounds are known to affect ambiguously the transformer oils characteristics. Therefore, it was of interest to study the individual sulfides as the inhibitory additives. The goal was achieved by the researches with the use of the model mixtures consisting of the selectively purified transformer oil (free from ionol) along with the individual sulfides, decylcyclohexylsulfide and decylfenylsulfide, at concentration of 0.5 %, Their effect on stability against oxidation of the selectively purified oil, on its electric strength and tangent of the dielectric losses’ angle was studied. The primary results obtained were, firstly, the rate slowing down of water formation in oil and of water-soluble acids formation in oil upon its oxidation in the presence of the individual sulfides, and, secondly, an increase in the electric strength and decrease in the dielectric losses compared to the transformer oil, containing ionol. It was established that decylcyclohexylsulfide inhibitory properties are stronger compared to those of decylfenylsulfide, which was testified by less quantities (by 1.8 times) of the water formed and of water-soluble acids (by 2.22 times). The introduction to oil of 0.5 % decylcyclohexylsulfide and decylfenylsulfide increased the oil electric strength, correspondingly, by 2.6 and by 5.5 times, upon water concentration in oil equal to 15·10-2 g/kg. The significance of the results obtained is in improving the transformer oil quality produced from the sulfur oils with the use of a novel additive.

Chemo-sensory characterization of aroma active compounds of native oak wood in relation to their geographical origins

Oak wood contains aroma-active compounds that contribute significantly to the chemical structure, olfactory and gustatory qualities of alcoholic beverages and vinegars as by-products that have been either fermented and/or aged in oak barrels. The chemical composition of cooperage oak is highly variable, depending on the degree of toasting and natural seasoning. However, it is unclear whether the odor of oak varies according to different geographical regions and pedoclimatic conditions. Especially in view of the actual challenges in forestry in relation to climate change, the present study aimed at elucidating the odorous constituents of nine natural oak samples from Germany, Austria and Hungary with respect to these influencing parameters. The odor profiles of the oaks were compared, the potent odorants were determined, and selected odorants were quantified using stable isotope dilution assays (SIDA). The majority of the identified odorants in all samples were fatty acid degradation products, followed by a series of odorants with terpenoic structure and others resulting from the degradation of lignin. Several different odorants including 2-propenoic acid and cinnamaldehyde are reported here for the first time in oaks from different growth regions. Odor activity values (OAVs), calculated based on odor thresholds (OTs) in water, revealed hexanal, (E)-2-nonenal, (Z)-3-hexenal, eugenol, vanillin, and whiskey lactone as potent odorants for the oak odor. Principal component analysis of the data obtained from sensory evaluation, comparative aroma extract dilution analysis (cAEDA) and their corresponding quantified odorants showed that the highest separation rate was obtained for Hungarian oak, whereas Austrian and Bavarian oak samples were more similar. Recombination experiments by mixing the dominant odorants in their naturally occurring concentrations revealed a good agreement of the smell properties of the model mixture with the smell of the respective original sample. These findings aimat evaluating and establishing a better understanding of the distinctive smell of oak wood and demonstrated the prospects of new oak sources.

An Automated Hydrodynamically Mediated Technique for Preparation of Calibration Solutions via Capillary Electrophoresis System as a Promising Alternative to Manual Pipetting.

In this paper, a novel procedure for preparing calibration solutions for capillary electrophoresis (CE)-based quantitative analysis is proposed. Our approach, named the automated hydrodynamically mediated technique (AHMT), uses a capillary and a pressure system to deliver the expected amount of working solution and diluent directly to a sample vial. As a result, calibration solutions are prepared automatically inside the CE instrument, without any or with minimal manual operation. Two different modes were tested: forward and reverse, differing in the direction of hydrodynamic flow. The calibration curves obtained for a model mixture of analytes using AHMT were thorough compared to the standard procedure based on manual pipetting. The results were consistent, though the volume of obtained calibration solutions and the potential risk of random errors were significantly minimized by AHMT. Its effectiveness was further enhanced by the application of SCIEX® nanoVials, reducing the actual volume of calibration solutions down to 10 μL.

STUDY OF DIAZINONE IN MODEL PREPARATIONS BASED ON METHANOL AND ISOPROPANOL BY HIGHLY EFFICIENCY LIQUID CHROMATOGRAPHY (HPLC)

The aim of the study was to investigate the stability of diazinon in two model mixtures in which the active substance content is 10%. Methyl and isopropyl alcohols were used as a basis for the production of model solutions with diazinon. According to the recipe of model drugs, methyl or isopropyl alcohols make up about half of the content of drug components.&#x0D; The diazinon content was determined by reversed-phase high performance liquid chromatography (HPLC) on 3, 14 and 21 days for the model mixture with methyl alcohol and on 14 and 50 days for the mixture with isopropyl alcohol.&#x0D; A significant number of publications have been devoted to the study of the degradation of diazinon and other nonspecific organophosphorus pesticides under the influence of various factors. However, it remains relevant to study this process in mixtures of a certain composition, in particular in new veterinary drugs under development. This article presents a comparison of the results of determination the content of diazinon in model mixtures based on methyl and isopropyl alcohols.&#x0D; The analyzes were performed on a Knauer liquid chromatograph with a spectrophotometric detector equipped with a Luna® Omega Polar C 18 150 × 4.6 mm column filled with a 5 μm sorbent of Phenomenex particle size with a 4 × 3.0 mm universal C 18 protective column. Mobile phase: degassed mixture of acetonitrile: water in the ratio 65:35, flow rate 1.1 ml / min at a column temperature of 20 °C, detection at a wavelength of 245 nm, injection volume - 0.050 ml, time of one separation - 20 minutes.&#x0D; It was found that the content of diazinon on the 21st day of storage of the model mixture based on methyl alcohol is about 30 % of the applied, while on the 50th day of storage of the model mixture based on isopropyl alcohol – 97 %.&#x0D; As we found in previous studies, the use of methyl alcohol is a probable factor in the breakdown of diazinon in the drug. The appearance of the peak of one of the products of diazinon for 3 min of the chromatogram of solutions of the production experimental preparation and the model mixture made in the HPLC laboratory with the solvent methanol was noted. When replacing methanol with isopropanol, the chromatogram of the drug solution did not show the appearance of an additional peak, except for the peak identified as diazinon. The use of isopropyl alcohol does not reduce the concentration of diazinon in the model mixture, as in the case of methanol. The composition with isopropyl alcohol provides relative stability of the model mixture.