Recent Advances in Combinations of TLC With MALDI and Other Desorption/Ionization Mass-Spectrometry Techniques

The combination of planar chromatography with desorption/ionization mass-spectrometry (MS) techniques provides chemists with unique tools for fast and simple separation of mixtures followed by the detection of analytes by the most powerful analytical method. Since its introduction in the early 1990s, thin-layer chromatography (TLC)/matrix-assisted mass spectrometry (MALDI) has been used for the analysis of a wide range of analytes, including natural and synthetic organic compounds. Nowadays, new desorption/ionization approaches have been developed and applied in conjunction with planar chromatography competing with MALDI. This review covers recent developments in the combination of TLC with various desorption/ionization MS methods which were made in recent several years.

Experimental testing of the effectiveness of novel hydrocyclones for separation of impurities in biofuels

This paper investigates the potential sources of renewable energy, in particular biofuels. Biofuels tend to contain multiple harmful impurities that need to be separated if the biofuel is to have good energy performance, and the systems that run on it to produce electricity or heat are to operate more reliably. The paper discusses use of hydrocyclones as the most productive and reliable biofuel purification method. It dwells upon the factors that negatively affect separation of mixtures in a hydrocyclone, which are attributable to the complex hydrodynamics of the flow in such a unit. In order to eliminate these factors, the authors hereof have developed two hydrocyclone designs. An experimental test bench was designed and made to test these designs. Parts of the units were 3D printed from an environmentally friendly material. For testing, we used a biodiesel made from waste cooking oil with an impurity content of 23%. Experiments showed a maximum separation rate of 94.2%. The proposed solutions did improve the effectiveness of biodiesel mixture separation. These designs can be effectively used to separate non-homogeneous mixtures.

DETERMINATION OF THE MODE OF FUNCTIONING OF THE CENTRIFUGAL-GRAVITATIONAL SEPARATOR OF THE GRINDING DEVICE

The peculiarity of harvesting legumes is the need to process their heap on grater devices with subsequent separation. To improve the technical and economic performance of seed heap processing equipment, it is advisable to combine wiping and separation operations by combining a grater working body and a separating rotating sieve of cylindrical or conical shape. The analysis of influence of geometry of rotary sieve drums allows to define the rational form and parameters of work of the separating device which will provide the necessary quality of seed material. Analysis of the literature on the processes of sieve separation of grain and seed mixtures showed the advantages of centrifugal separators with a rotating sieve surface. Improving the efficiency of separation of mixtures by rotary sieves is achieved by the simultaneous use of centrifugal, Coriolis and gravitational forces. The aim of the study is to increase the efficiency of separation of seed heaps of legumes after treatment with a grater device by determining the trajectory of the seeds along the rotational surfaces. Earlier, the authors developed a grater-separating unit in which a cylindrical perforated drum is used to remove unworn seeds. This design does not use the surface of the sieve effectively enough. To increase the uniformity of the load on the steaming surface of the rotary drum, it is advisable to reduce its area in the direction of seed movement. To do this, use a conical separating surface to reduce the radius of the cone in the direction of movement of the material. When considering the movement of a particle, it is represented as a material point with mass m moving along a conical surface that rotates around a vertical axis. As a result of theoretical researches the dependence which defines time of stay of a particle on a sieve depending on a coordinate (length of a generating cone) is received. A graphical interpretation of this dependence for certain values of design parameters is also presented. As a result of research, it was found that increasing the residence time of the material on the sieve due to the use of a conical surface increases the yield of pure seeds, and also contributes to the uniform loading of the sieve surface, which improves the quality of the source material.

A Review on Mixed Matrix Membranes for Solvent Dehydration and Recovery Process

Solvent separation and dehydration are important operations for industries and laboratories. Processes such as distillation and extraction are not always effective and are energy-consuming. An alternate approach is offered by pervaporation, based on the solution-diffusion transport mechanism. Polymer-based membranes such as those made of Polydimethylsiloxane (PDMS) have offered good pervaporation performance. Attempts have been made to improve their performance by incorporating inorganic fillers into the PDMS matrix, in which metal-organic frameworks (MOFs) have proven to be the most efficient. Among the MOFs, Zeolitic imidazolate framework (ZIF) based membranes have shown an excellent performance, with high values for flux and separation factors. Various studies have been conducted, employing ZIF-PDMS membranes for pervaporation separation of mixtures such as aqueous-alcoholic solutions. This paper presents an extensive review of the pervaporation performance of ZIF-based mixed matrix membranes (MMMs), novel synthesis methods, filler modifications, factors affecting membrane performance as well as studies based on polymers other than PDMS for the membrane matrix. Some suggestions for future studies have also been provided, such as the use of biopolymers and self-healing membranes.

Matrix-Assisted DOSY for Analysis of Indole Alkaloid Mixtures

Diffusion-ordered spectroscopy (DOSY) is a powerful tool for investigating mixtures and identifying peaks of chemical components. However, similar diffusion coefficients of the components, particularly for complex mixtures that contain crowded resonances, limit resolution and restrict application of the DOSY technique. In this paper, matrix-assisted DOSY were used to explore whether the diffusion resolution of a complex model involving indole alkaloid mixtures can be realized. Furthermore, we investigated the influence of different factors on the separation effect. The results showed that the changes in diffusion coefficient differences were achieved more obviously when using sodium dodecyl sulfate (SDS) micelles as the matrix. In addition, we also found that increasing the concentration of SDS can improve the resolution of the DOSY spectrum. Finally, after investigating the influence factors and NMR conditions, we demonstrated the applications of the SDS-assisted DOSY on analyzing the total alkaloid extract of Alstonia Mairei, and the virtual separation of mixtures was achieved.

Charge-driven condensation of RNA and proteins suggests broad role of phase separation in cytoplasmic environments

Phase separation processes are increasingly being recognized as important organizing mechanisms of biological macromolecules in cellular environments. Well-established drivers of phase separation are multi-valency and intrinsic disorder. Here, we show that globular macromolecules may condense simply based on electrostatic complementarity. More specifically, phase separation of mixtures between RNA and positively charged proteins is described from a combination of multiscale computer simulations with microscopy and spectroscopy experiments. Phase diagrams were mapped out as a function of molecular concentrations in experiment and as a function of molecular size and temperature via simulations. The resulting condensates were found to retain at least some degree of internal dynamics varying as a function of the molecular composition. The results suggest a more general principle for phase separation that is based primarily on electrostatic complementarity without invoking polymer properties as in most previous studies. Simulation results furthermore suggest that such phase separation may occur widely in heterogenous cellular environment between nucleic acid and protein components.

Dean Vortex for Laminar Flows in Curved Pipes with Various Cross-Sections

Curved pipes flows are encountered in different areas such as heat transfer, chaotic mixing, separation of mixtures in pipes, or blood circulation among others and exhibit a variety of characteristics depending on the ranges of Dean numbers and pipe curvatures. Studies on curved pipes flows usually consider the cases of circular, elliptical, and rectangular shapes for the cross sections of the pipe. The present work extends the availability of asymptotic analytical solutions to new ranges of cross-sectional shapes while considering fully developed steady state flows at low Dean numbers. The new shapes are given by a polar equation R* (q) satisfying the relation 1-R^(*2) (q)+dR^(*y) (q)sin(yq)=0 where d and y are parameters. The zero-order azimuthal velocity profiles for various cross-sections are given by exact analytical solutions. Solutions for the nonhomogeneous biharmonic equation for the secondary flows are given by using exact expressions for the particular solutions. Furthermore, the Fourier series decomposition of the solution is adopted to determine the integration constants that allow satisfying the non-slip boundary conditions. Solutions are presented for semi triangular (y=3) , square (y=4), and pentagonal (y=5) cross sections shapes. It is found that the velocity distribution and the Dean’s vortexes intensities are modified in function of the cross-section shapes.

Assessment of the Electrostatic Separation Effectiveness of Plastic Waste Using a Vision System

The work presented here describes the first results of an effective method of assessing the quality of electrostatic separation of mixtures of polymer materials. The motivation for the research was to find an effective method of mechanical separation of plastic materials and a quick assessment of the effectiveness of the method itself. The proposed method is based on the application of a dedicated vision system developed for needs of research on electrostatic separation. The effectiveness of the elaborated system has been demonstrated by evaluating the quality of the separation of mixtures of poly (methyl methacrylate) (PMMA) and polystyrene (PS). The obtained results show that the developed vision system can be successfully employed in the research on plastic separation, providing a fast and accurate method of assessing the purity and effectiveness of the separation process.

SILICA GEL MODIFICATION BY NICKEL(II) COMPLEXES WITH NITROGEN- AND OXYGEN-CONTAINING ORGANIC LIGANDS FOR GAS CHROMATOGRAPHY

Gas chromatographic sorbents based on Siloсhrome S-80 adsorptively modified with 8-hydroxyquinolinate, 1-phenylazo-2-naphtholate and 2-nitroso-1-naphtholate of nickel(II) have been obtained. It has been established that the thermal stability (up to 170–350 °C) of chelate-containing sorbents is sufficient for carrying out gas chromatographic separations. The IR and Raman spectra of the obtained materials confirmed the success of the complexation processes in the synthesis of complex nickel(II) compounds and the retention of coordination bonds after the deposition of chelates on silica gel. The characteristics of the surface and the porous structure of the prepared sorbents are investigated. As a result of adsorptive modification of Silochrome S-80 with nickel(II) chelates, it’s specific surface area (84 m2/g) decreases by 12–32 m2/g along with a decrease in the average pore size, which indicates the fixation of modifiers at the edges of large pores. It was shown that modification of Silochrome S-80 with 8-hydroxyquinolinate, 1-phenylazo-2-naphtholate, 2-nitroso-1-naphtholate of nickel(II) has a significant effect on the chromatographic polarity and selectivity of sorbents. The presence of a polar nitroso-groups in the composition of nickel(II) 2-nitroso-1-naphtholate makes the metal center more accessible for donor-acceptor interactions with sorbates (pyridine, carbonyl compounds). Also, the nitroso-group is active in the formation of hydrogen bonds with alcohols, which complicates their elution at column temperatures below 170 °C. The greatest affinity to the homologous of arenes is shown by silochrome modified by a nickel(II) complex with the least bulky 8-hydroxyquinolinate ligands, which leads to an increase in the retention times of aromatic and polyaromatic compounds along with an increase of the sorbent selectivity. The possibility of practical application of a chromatographic column filled with Silochrome S-80 with deposited nickel(II) 8-hydroxyquinolinate for gas chromatographic (FID) separation of mixtures of polyaromatic compounds in the temperature programming mode is shown.