Preliminary Separation Research Articles

Multivariable Manipulation of Spectrophotometric Data with Genetic Algorithm Selection for Novel Quantitative Resolution of Five Antiviral Drugs in Their Pharmaceutical Products.

In many real-world situations there are many components in a mixture that produce an enormous amount of information. The main task is to build up balanced models that convert these data into meaningful information to deal with. Hence, different chemometric models were applied for the analysis of data obtained from a mixture containing sofosbuvir, ledipasvir, velpatasvir, daclatasvir, and valacyclovir that were recently used internationally for their antiviral activity. Partial Least Squares, Spectral Residual Augmented Classical Least Squares, and Concentration Residual Augmented Classical Least Squares designs were applied with and without variable selection procedure [Genetic Algorithm (GA)]. The methods were used for the quantitative analysis of the drugs in laboratory prepared mixtures and real market sample through handling the UV spectral data. Robust models were obtained by applying GA. The proposed methods were found to be rapid, simple, and required no preliminary separation steps. These models can be used on a routine basis in quality control laboratories or factories giving competitor results to those obtained by the reported methods. The proposed models offer a powerful analytical alternative for laboratories that consider economic strategies in their requirements.

Synthesis, Isolation and Characterization of three acid and alkaline hydrolytic products of Nimodipine and Development of a valid RP-HPLC method for simultaneous determination of Nimodipine and Citicoline sodium in the presence of Nimodipine degradation products in Bulk and Tablets

Impurity profiling of active pharmaceutical ingredients is a crucial step in assessing their quality. Moreover, the chemical nature of nimodipine makes it susceptible easily to acidic and alkaline hydrolysis. On the other hand, nimodipine is co-formulated with citicoline sodium pharmaceutically as tablets to treat cerebral ischemia. In this study, three degradation products of nimodipine were synthesized, isolated and characterized with aid of FTIR spectroscopy, 1H-NMR as well as LC-MS/MS after exposing to drastic acidic and alkaline conditions. Subsequently, a simple, selective and valid RP-HPLC method was developed for simultaneous estimation of nimodipine and citicoline in the presence of nimodipine acid and alkaline degradation products in bulk and tablets. Chromatographic separation was achieved using an isocratic mobile phase consisting of acetonitrile: 0.02 M KH2PO4 (containing 0.2% v/v, triethylamine and adjusted to pH 3.0 with orthophosphoric acid) (70:30, v/v) at a flow rate 1.0 mL min-1 at ambient temperature (25 ºC) on a Eurospher II C18 (250 mm × 4.6 mm, 5 µm) column with UV detection at 270 nm for citicoline and 235 nm for nimodipine and its acidic and alkaline hydrolytic products. Linearity, accuracy and precision were found to be acceptable over a concentration range of (4.5–120 μg mL-1) for nimodipine and (15–400 μg mL-1) for citicoline. The proposed method could be successfully applied for the routine analysis of the studied drugs in their pharmaceutical preparation in the presence of nimodipine common degradation products without any preliminary separation step.

New HPPOa technology for propylene oxide production: from laboratory reactor to commercial pilot installation

The development of HPPOa technology on production of propylene oxide from propylene and hydrogen peroxide with the use of acetonitrile as a solvent instead of methanol is shortly described. Laboratory studies included the development of a new catalyst and its testing in a flow fixed bed (4-10 cm3) reactor at 40-550C/3.0 MPa. Proposed TIS-1 catalyst was synthesized using dispersed Newsil 115 silica instead of traditional TEOS for TS-1 zeolite obtaining. Silica Ludox 40 and starch were used in the synthesis of TIS-1 catalyst also. On the basis of determined molar composition of reaction 60% H2O2 - propylene- 85% acetonitrile mixture and a load on catalyst the HPPOa (hydrogen peroxide to propylene oxide in acetonitrile) technology for a pilot installation with capacity of 2000 t/y has been developed. The main equipment – 3 reactors, 6 distillation columns, absorber, heat exchangers were made in Ukraine by Techinservice Manufacturing Group Ltd. At the beginning 2019, the construction of HPPOa installation at the olefin plant of Karpatnaftochim Ltd in Kalush began. The first start of this installation took place in June 2020. That is, in a very short time, 3 years after the start of laboratory tests. Technological HPPOa scheme includes epoxidation of propylene, preliminary separation of the product mixture, purification of propylene oxide, propylene compression, purification of propylene from propane, absorption of propylene with acetonitrile, regeneration of acetonitrile. The installation is a rather complex engineering system, some elements of which operate under both high (30 atm) and low (0.1 atm) pressure at temperatures from -30 to 1500C. Now the installation is brought to design capacity with the production of commercial propylene oxide with a polymer purity of 99.95% without the use of traditional ammonia and hydrazine. Fully automated installation is serviced by 4 operators working in two shifts. Consumption of 100% H2O2 and propylene per 1 ton of propylene oxide consists 0.68 and 0.75 tons, respectively. Ltd ”Karpatnaftochim” intends to build a facility for production of propylene oxide with a capacity of 130,000 tons per year using HPPOa technology.

Construction of PA6-rGO nanofiber membrane via electrospraying combining electrospinning processes for emulsified oily sewage purification

• PA6-rGO composites were synthesized through in situ ring-opening polymerization • PA6-rGO membrane was constructed by combining electrospinning and electrospraying • Super hydrophilicity and underwater super oleophobicity were effectively integrated • Stable membranes with good oil droplet rejection were obtained The construction of highly efficient membranes toward oil/water separation is crucial in severe oily sewage treatment while graphene materials are considered stable blocks for oil/water separating membranes. Herein, first, with the presence of graphene oxide, in-situ polymerization of caprolactam was carried out and polyamide-6-reduced graphene oxide composites (PA6-rGO) were successfully synthesized. Then the PA6-rGO nanofiber membranes were prepared by electrospinning combining electrospraying process. Nanofiber skin with microshphere/bead fiber structure on the surface of ordinary electrospun fiber membrane was prepared in 2 steps. Hence the nanofiber membrane separation performance to emulsions under gravity driving was investigated. The results showed that the flux of surfactant-stabilized emulsions would reach up to 765.4 Lm −2 ·h −1 with the rejection up to 99.6%. It is expected to be practically applied in a low-pressure driven membrane separation system to achieve preliminary separation of severe oily sewage.

Recovery of molybdenum from uranium raffinate solution containing phosphorus

ABSTRACT Ion exchange-predominance precipitation process was brought forward to extract Mo from P and sulfate system. Adsorption property and effect law were studied, and the adsorption mechanism was discussed. Influence relation of predominance precipitation for calcium salt was calculated, and corresponding verification tests were conducted. The results indicated that preliminary separation of P and Mo was realized by employing of D380 resin and the further removal of P from the qualified Mo eluted by strongly alkaline was achieved through predominant precipitation. Mass fraction of P in calcium molybdate product was 1 –2% and the recovery rate of Mo could reach to 98%. Under the technological background of uranium extraction, this study solved the problem of extracting trace Mo from the high P system and realized the separation of Mo from P and a small amount of U.

A comparative study of novel spectrophotometric methods for simultaneous determination of nitroaniline isomers in their binary mixtures with highly severe overlapping spectra

In the present work, four simple and economic spectrophotometric methods, namely constant center (CC), ratio difference (RD), H-point standard addition method (HPSAM), and ratio H-point standard addition method (RHPSAM) were employed for the simultaneous determination of meta and para-nitroaniline with severely overlapping spectra without unitizing the preliminary physical separation techniques. In each method, the parameters affecting the resolution of the spectra were optimized to determine the cited isomers in a binary mixture with a high accuracy. Under the optimized conditions, the results obtained showed that from cited methods used, the CC and RD methods have the least errors in determination of the concentration of highly spectral overlapping species. The mean percentage recovery values for the binary mixture of meta- and para-nitroaniline were found to be 95.98 and 98.78 using the RD method, and 101.85 and 100.23 using the CC method, respectively. For comparison of the powerful multivariate methods including the principal component regression (PCR) and partial least squares (PLS) were also applied. The mean percentage recovery values for the binary mixtures of the cited isomers were found to be 101.62 and 101.47 using the PCR method, and 101.00 and 101.36 using the PLS method, respectively. A statistical comparison of the methods demonstrated that there was no significant difference between the RD, CC, PCR, and PLS methods and the reported HPLC method regarding both accuracy and precision. The proposed methods have an admissible precision and accuracy for determination of the two isomers in their binary mixtures in tap water as a real sample.

Study of the operation of a combine harvester cleaning system with a sieve screw separator in the conditions of operation on slopes

The article presents the results of studies of a cleaning system with a sieve screw separator in operation conditions of a combine harvester on slopes. The grain heap in the proposed cleaning system is moved by screws, which ensures uniform feeding of the grain heap to the upper sieve with longitudinal tilts of the combine. Autonomous operation of the screws reduces the uneven distribution of grain heaps across the width at the beginning of the upper sieve of the cleaning system. Preliminary separation of grain reduces the grain flow to the upper sieve by more than 60%. Laboratory studies have shown a decrease in grain loss with a transverse tilt of the combine of 8 degrees from 1.17% in the compared treatment system to 0.75% in the treatment system with a sieve screw separator. An additional reduction in grain losses was achieved by installing longitudinal partitions with a height of 0.13 m on the upper sieve, preventing the grain heap from shifting sideways on the upper sieve. The theoretical coefficient of variation in the grain heap layer thickness at the end of the upper sieve is 0.18. Grain losses in the proposed cleaning system, calculated by the mathematical model of separation, amounted to 0.14%, which is 8 times lower than the compared cleaning system.

Bioactive Compounds from the Endophytes of Datura Metel L

The present study aims to investigate the preliminary phytochemical screening and various separation techniques to isolate the bioactive compounds from the endophytes of Datura metel. The ethyl acetate extracts of the endophytes are used for the current study. Phytochemical screening of the extracts revealed the presence of tannins, alkaloids, terpenoids and tropane alkaloids. The quantitative amounts of tropane alkaloids are significant in actinomycete (29.4%) than the endophytic fungus (23.2%). Actinomycete seems to contain higher phenolic content of 1. 271 mg/g whereas endophytic fungus accounts only 1.254 mg/g. The IR spectroscopic studies of endophytic fungus and actinomycetes showed peaks at different points and the results are noted. Hence, the isolation and production of bioactive compounds from the endophytes may facilitate the new product discovery process.

Univariate and multivariate assisted spectrophotometric methods for determination of rosuvastatin calcium and fenofibrate in bulk powders and tablets along with their degradation products

Rosuvastatin calcium and fenofibrate are recently co-formulated for treatment of hyperlipidemia. Two selective spectrophotometric approaches were developed, the first is univariate manipulation of spectrophotometric data, where isoabsorptive point and dual wavelength method were applied. The total concentration of rosuvastatin calcium and fenofibrate could be determined at λ = 253.2 nm while rosuvastatin calcium was determined with dual wavelength (λ = 243.5 and 307.9 nm) where linearity was achieved in the range of 2.00–22.00 µg/mL and mean accuracy 100.29 ± 0.568 then, by difference, Fenofibrate was determined in the range of 2.00–22.00 µg/mL and mean accuracy 100.23 ± 0.578. The second approach is a stability indicating multivariate modeling namely principal component regression and partial least squares, where the two drugs were determined in the presence of their degradation products. 17 samples were prepared according to five levels four factors calibration design. The developed models were described by 4 latent variables, and good prediction was evidenced by low root mean square error of prediction. The proposed methods were found to be rapid and simple and required no preliminary separation. Rosuvastatin calcium and fenofibrate were analyzed with mean recoveries 99.54 ± 0.903, 99.88 ± 0.548 and 99.50 ± 0.712, 99.30 ± 0.802, respectively. The two drugs were successfully determined in tablets by the developed methods and the results were compared to HPLC methods, where they were found to be statistically non-significant.

Detection reagents used for on-plate identification of organic pesticides in biological samples with preliminary separation by TLC/HPTLC

Many specific and non-specific chromogenic spray reagents have been used to detect organic pesticides (organophosphorus, organochlorine, carbamates, and pyrethroids) on thin-layer chromatographic (TLC)/high-performance thin-layer chromatographic (HPTLC) plates. To realize high sensitivity and improved selectivity, several chromogenic reagents have been introduced. The physical properties of organic pesticides reported so far are also presented in tabular form. The colors produced on TLC plates due to reactions taking place between pesticides and spray reagents are illustrated in the form of chromatograms, and reaction mechanism is also presented.

Pickering Emulsions of Fluorinated TiO2: A New Route for Intensification of Photocatalytic Degradation of Nitrobenzene.

Fluorination of the TiO2 surface has been often reported as a tool to increase the photocatalytic efficiency due to the beneficial effects in terms of production of oxidizing radicals. Moreover, it is shown that the unique amphiphilic properties of the fluorinated TiO2 (TiO2-F) surface allow one to use this material as a stabilizer for the formulation of Pickering emulsions of poorly soluble pollutants such as nitrobenzene (NB) in water. The emulsions have been characterized in terms of size of the droplets, type of emulsion, possibility of phase inversion, contact angle measurements, and optical microscopy. The emulsified system presents micrometer-sized droplets of pollutant surrounded by the TiO2-F photocatalyst. Consequently, the system can be considered to be composed of microreactors for the degradation of the pollutant, which maximize the contact area between the photocatalyst and substrate. The enhanced photocatalytic activity of TiO2-F was confirmed in the present paper as the apparent rate constants of NB photodegradation were 16 × 10–3 and 12 × 10–3 min–1 for fluorinated and bare TiO2, respectively. At NB concentrations largely exceeding its solubility, the rate constant was 0.04 × 10–3 min–1 in the presence of both TiO2 and TiO2-F. However, unlike TiO2, TiO2-F stabilized NB/water emulsions and, under these conditions, the efficiency of NB photocatalytic degradation in the emulsified system was ca. 18 times higher than in the nonemulsified one. This result is relevant also in terms of practical applications because it opens the route to one-pot treatments of biphasic polluted streams without the need of preliminary physical separation treatments.

Univariate and Chemometrics-Assisted Spectrophotometric Methods for Determination of Flibanserin in a Recently Released Dosage Form

Five simple, selective, and rapid spectrophotometric methods are developed for the determination of flibanserin (FL) in the presence of its oxidative degradation products (ODPs). Stress studies are performed according to the International Conference on Harmonization (ICH) guidelines to assess the behavior of FL against oxidative, thermal, and acidic conditions. FL was stable against thermal and acidic conditions, while it was susceptible to oxidative degradation. Three of the spectrophotometric methods were univariate methods, namely, third derivative (D3), ratio difference of ratio spectra (RD), and first derivative ratio of spectra (D1R), while the other two methods were multivariate methods, namely, partial least square (PLS) and principal components regression (PCR). No preliminary separation steps were required in these methods. The chemical structures of the ODPs were confirmed using mass spectrometry and 1H NMR spectroscopy. The proposed methods were developed and validated according to the ICH guidelines. The linearity, accuracy, and precision were determined, and the selectivity was assessed by analyzing synthetic laboratory mixtures containing different ratios of FL and its ODPs. Statistical comparisons were applied to the five spectrophotometric methods, and no significant differences were found. The validated methods could be applied for routine testing and quality control.

Development of methods for determination of impurity elements in zircon-alumo-ytterbium ceramic materials for medical purpose

Determining the presence of impurities, carcinogenic and harmful elements in the synthesized materials is a necessary step to identify the field of application, especially for medicine. Methods have been developed for the atomic emission with inductively coupled plasma (AES-ICP) for simultaneous quantifying of impurities contents: Al, As, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Si, Ti, Y, Yb, Hf, V, Zn in new zircon-alumo-ytterbium ceramic materials for medical use. Various schemes for dissolving samples were offered for different types of ceramic compounds. Elements were determinate with founded optimal analytical parameters. The influence and methods elimination of matrix elements (Zr, Al, Yb) were studied. It allowed to determine elements with good metrological characteristics in a wide range of concentration from 1·10-3 to n·10% without preliminary separation of the matrix and without using solid standard samples. The relative standard deviation (Sr) does not exceed 0.12.

Biosynthesis of Tacrolimus by the Streptomyces tsukubensis VKM Ac-2618D Strain in the Presence of Polymeric Sorbents and Development of a Method for Its Isolation and Purification

Tacrolimus is known as the most effective immunosuppressive drug which is synthesized by actinobacteria of the genus Streptomyces. Its biosynthesis is accompanied by the formation of the structural analogs. A new method for the production of tacrolimus by Streptomyces tsukubensis BKM Ac-2618D with the use of brominated styrene-divinylbenzene sorbent SP-207 was developed. This approach enabled to increase the yield, prevent undesirable destruction, and simplify the tacrolimus isolation procedure from the cultivation media. The preliminary separation step was optimized by means of the usage of regenerable sorbents such as methylmethacrylate (HP2MG) and chemically modified silica gel (Diasorb-100-Diol). By implementation of the silica gel-based cation exchange resins pretreated with silver ions for the final purification stage, it was possible to increase its productivity. The overall yield of tacrolimus by this method was found to around 60–70%. The results could be implemented for the full-cycle production development of the pharmaceutical grade tacrolimus.

Determining the quality of milk fat dispersion in a jet-slot milk homogenizer

One of the urgent problems in the dairy industry is to reduce power input in the process of dispersing milk fat while ensuring a high degree of homogenization. This problem can be solved through the development and implementation of a virtually unexplored jet-slot milk homogenizer. The principle of its action implies the preliminary separation of cream from whole milk and its feed into the high-velocity flow of skim milk. The homogenization process occurs by creating a sufficient difference in velocities of the disperse and dispersing phases of the milk emulsion, which is mathematically described by Weber's criterion. Experimental studies of the effect of fat content in cream, cream feed rate, and width of the annular slot on dispersion indices during processing in the designed homogenizer have been carried out. The mathematical dependence which relates these parameters was found. It was proved that to obtain a milk emulsion with a dispersion level of 0.8 μm, the width of the annular slot should be 0.1–0.5 mm, fat content in cream 40–50 %, and the feed rate less than 40 m/s. The results of the evaluation of dispersion quality show a 7 % decrease in the average diameter of the fat globules compared to the most common values obtainable in the valve homogenizer. A refined critical value of the Weber criterion for dispersion of the fat phase of milk was determined (29 units) which indicates an increase in the intensity of the homogenization process in comparison with the jet milk homogenizer with a separate cream feed. The derived critical value of the criterion is necessary to create a theory of the process of dispersing milk fat and develop more efficient designs of milk homogenizers

Study on the Relations between Hyperspectral Images of Bananas (Musa spp.) from Different Countries, Their Compositional Traits and Growing Conditions.

Bananas are some of the most popular fruits around the world. However, there is limited research that explores hyperspectral imaging of bananas and its relationship with the chemical composition and growing conditions. In the study, the relations that exist between the visible near-infrared hyperspectral reflectance imaging data in the 400–1000 nm range of the bananas collected from different countries, the compositional traits and local growing conditions (altitude, temperature and rainfall) and production management (organic/conventional) were explored. The main compositional traits included moisture, starch, dietary fibre, protein, carotene content and the CIE L*a*b* colour values were also determined. The principal component analysis showed the preliminary separation of bananas from different geographical origins and production systems. The compositional and spectral data revealed positively and negatively moderate correlations (r around ±0.50, p < 0.05) between the carotene, starch content, and colour values (a*, b*) on the one hand and the wavelength ranges 405–525 nm, 615–645 nm, 885–985 nm on the other hand. Since the variation in composition and colour values were related to rainfall and temperature, the spectral information is likely also influenced by the growing conditions. The results could be useful to the industry for the improvement of banana quality and traceability.

Determination of biogenic amines by using amperometric biosensors based on grass pea amine oxidase and oat polyamine oxidase

Grass pea amine oxidase (GPAO) and oat polyamine oxidase (OPAO) were immobilized along with horseradish peroxidase (HRP) and an Os-redox polymer (Os-RP) onto the surface of a graphite electrode by crosslinking with poly(ethylenglycol) diglycidyl ether. The resulted reagentless amperometric biosensors were inserted in a flow injection setup and used as electrochemical detectors for the biogenic amines (BA) detection. Both biosensors were operated at low applied potential (-50 mV vs. Ag/AgCl, KCl0.1M) where electrochemical interferences are minimal. The quantification of ten BA (tyramine, putrescine, cadaverine, histamine, cystamine, phenylethylamine, agmatine, tryptamine, spermine, and spermidine) either individual or in mixture (after a preliminary separation by using cation exchange chromatography) was reported. G/(Os-RP)-HRP-GPAO biosensor detected all ten BA, while G/(Os-RP)-HRP-OPAO biosensor detected only spermine and spermidine. Finally, a simple and low-cost method for free and acetylated polyamines determination in human urine samples, by using the highly selective G/(Os-RP)-HRP-OPAO biosensor, was proposed. (Less)

Computationally efficient optimization models for preliminary distillation column design and separation energy targeting

We propose versatile shortcut distillation column and separation energy targeting models that are well-suited for superstructure-based process synthesis. The models are based on a novel reformulation of the Underwood equations to address systems where the components that are present in the feed can vary due to zero flow rates of some components. Also, we propose valid constraints, resulting in a significant enhancement of the computational performance of the models. The proposed distillation column model can automatically identify adequate key components and the energy requirement of a desired separation task, while considering a wide range of types of separations including non-sharp/sloppy splits. Also, the proposed separation energy targeting model can be used to estimate an energy requirement target for the separation of a mixture without finding detail network configurations. Due to their versatility and computational efficiency, the proposed models can be readily used for and expand the scope of superstructure-based process synthesis approaches.

How do colloid separation and sediment storage methods affect water-mobilizable colloids and phosphorus? An insight into dam reservoir sediment

Despite the significant role played by colloids in determining the fate of contaminants in aquatic systems, obtaining knowledge about the mobilizable colloids from bottom sediments of dam reservoirs has not yet received sufficient consideration. A major obstacle to understanding the role of colloids in aquatic systems is the limited comparability of results with the literature due to the vast number of methods practiced for colloid extraction/separation and the various sample storage conditions used for colloid extraction purposes.This work presents the effects of five colloid separation methods (namely direct filtration, successive filtrations, low-speed centrifugation and filtration, high-speed centrifugation and filtration, and successive centrifugations), combined with four sediment storage modes (wet, air-dried at 20 °C, oven-dried at 40 °C, freeze-dried), on the characteristics (mass, size distribution, composition) of water-mobilizable colloids from the bottom sediment of an eutrophic reservoir (Champsanglard, France). Special attention has been paid to phosphorus (P), an element that occupies a predominant place in the study of eutrophication process.Results showed that Champsanglard sediment contained a relatively high stock of water-mobilizable colloids (over 5.4 g/kgDW-Sed), along with the associated colloidal P constituted of approximately 4 % total sedimentary P and 81 %–93 % total water-mobilizable P (fraction < 1 μm). The mass and size distribution of released colloids, as well as the amount of colloidal and dissolved P, Corg, Fe, Ca, Mn, Al and Mg, differed by a factor of up to 26 depending on colloid separation protocols. The loss in colloidal mass upon membrane clogging during direct filtration was mitigated by means of a preliminary separation of particles through filtration and centrifugation, while successive centrifugations led to the potential overestimation of colloid quantity due to incomplete separation caused by presence of organic matter. Sediment storage impacts at a greater extent on extracted colloidal mass. In comparison with fresh sediment, drying decreased up to 40 folds the amounts of colloidal and dissolved elements. Special attention should be paid to sediment storage and separation protocols. According to our results, the characterization of colloids shall be done on fresh sediment and with separation by successive filtrations or combination of centrifugation and filtration. The comparison between sediment of different reservoirs should be based on similar application of sample storage and colloid separation protocol, the definition of normalized protocol would be thus required. It is strongly advised to avoid using solely centrifugation for colloid recovery and sediment freeze-drying for long-term storage when working with sediments.

Preparation of chiral izobenzofuranes based on 3-carene in the presence of halloysite nanocatalysts

The reaction of a 2-carene containing mixture, obtained by 3-carene isomerization, with 4-methoxybenzalde-hyde in the presence of halloysite nanotubes treated with 5.0 % HCl was studied. The main reaction products are the chiral derivatives of isobenzofuran. Selectivity to these compounds (71.4 %) is comparable to that when only 2-carene is used as a reactant. Thus, the possibility is shown how to use halloysite nanocatalysts for selective production of isobenzofuran compounds based on 3-carene isomerization products (major component of turpentine) without preliminary mixture separation.