Silica Gel Layers Research Articles

Metal/covalent organic framework@silica double-layer core–shell composite: A high-performance liquid chromatographic stationary phase

Nowadays, metal/covalent organic frameworks (MOFs/COFs) have shown bright application prospects in the field of chromatographic separation due to their unique porous characteristics. However, chromatographic stationary phases prepared with only a single MOF or COF material have a few inherent defects, which keep them from satisfying the actual application fully. In contrast, MOF/COF composites have more superior properties that are more favorable for separation. Therefore, this study innovatively proposed a new strategy to apply MOF/COF modified silica composites for high performance liquid chromatography (HPLC). To be specific, using ethylenediamine as a linker, Zn-based MOF and imine-based COF were modified on the aminated silica gel layer by layer, and a MOF-5/COF@silica bilayer core–shell composite was successfully prepared. The composite of MOF and COF can complement each other in realizing the advantages of the two materials. The research results show that the MOF-5/COF composite can provide a large number of active sites with a variety of interaction forces for the analytes. The MOF-5/COF@silica stationary phase can separate a wide range of hydrophilic and hydrophobic substances, which can also be used for the effective detection of environmental hormones in lake water samples. This study verifies the feasibility of preparing MOF and COF co-modified silica gel composite to improve the separation performance of stationary phase, and demonstrates the superiority of the double-layer porous core–shell structure for efficient HPLC analysis. This provides a new idea for the further development and application of porous materials in the field of HPLC.

Exploring antioxidant potential in two basidiomycetous mushrooms using high-performance thin-layer chromatography–DPPH–videodensitometry

The antioxidant activity of the methanol extracts of fruiting bodies of two basidiomycetous mushroom species (Cyclocybe cylindracea and Leccinum duriusculum) was evaluated by high-performance thin-layer chromatography (HPTLC) combined with 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay and videodensitometry. The HPTLC separation was achieved on a silica gel layer with acetonitrile–water–acetic acid (75:25:3, V/V). The results were compared with those obtained by the conventional microplate-based DPPH assay. The two methods provided similar results showing that the extract of the C. cylindracea had higher total antioxidant activity than the extract of the L. duriusculum, and the antioxidant activities of both extracts were much weaker than the antioxidant activities of ascorbic acid or gallic acid. Mushroom components in one zone of L. duriusculum extract and three zones of C. cylindracea extract assigned using HPTLC–DPPH–videodensitometry were mainly responsible for the antioxidant activity. Based on a previous study the β-carboline alkaloid C1-S diastereomer of brunnein B in C. cylindracea at hRF 49 contributed to the antioxidant effect the most, which corresponded to 52.0 ± 3.1 ng of ascorbic acid equivalent and 51.7 ± 3.7 ng of gallic acid equivalent.

PV thermal regulation and water harvesting hybrid system using evaporative cooling of silica gel layer

A proposed system for a passive cooling technique of photovoltaic (PV) via desorption cooling and water harvesting using a silica gel layer is investigated numerically. The harvested water is discussed, and the performance of the desorption-cooled PV is compared with the naturally cooled PV cell. The silica gel layer provides the water needed for evaporative cooling, so the proposed system can be used where water does not exist. The system model is presented, solved using MATLAB, and validated. The impact of the ambient conditions (ambient temperature and relative humidity), solar intensity, and silica gel layer thickness on the PV performance and silica gel uptake are presented for constant conditions and transient input weather conditions. The findings show a considerable reduction in the cell temperature and an enhancement in the cell efficiency. Also, The harvested water quantities are obtained at different operating conditions and layer thicknesses. At constant input conditions, a maximum reduction in the average PV cell temperature of 16.18 °C and an efficiency enhancement of 8.76% are achieved using a silica gel layer of 1 cm thickness. In addition, the maximum harvested water is reported as 1.238 kg/m2 for 2 cm layer thickness. For transient input weather conditions, the same performance enhancement with a reduced daily average cell temperature of 7 °C and an efficiency enhancement of 4.8% is achieved at the different silica gel layer thicknesses during 13 hr of simulation. Also, the maximum harvested water is reported as 2.35 kg/m2 for 3 cm thickness. Increasing the silica gel layer thickness influences the cell performance adversely under constant operating conditions, while this effect vanishes for actual transient input weather conditions. In contrast, increasing the thickness layer can increase the harvested water, which depends on the incident flux.

Cytotoxicity Activity, Metabolite Profiling, and Isolation Compound from Crude Hexane Extract of Cleome rutidospermae.

This study isolated the chemical compounds and evaluated the cytotoxic activity of the crude hexane extract of Cleome rutidospermae herb (CRH). The isolate was purified using silica gel, column chromatography, and preparative thin layer chromatography (PTLC). Furthermore, the structure of the compounds was identified by spectroscopic methods using 1D, 2D NMR, and mass spectrometry. The cytotoxic activity of CRH at a concentration of 20 ug/mL was also tested against MCF-7, A549, KB, KB-VIN, and MDA-MB-231 cancer cells using the sulforhodamine B (SRB) method. The CRH contained compounds of unsaturated fatty acid, saturated fatty acid, lipid, glycerol, ω-3 fatty acid, and cholesterol. Two compounds were obtained from the plant, and their structures were identified as (1) Stigmasta-5,22-dien-3-ol (STML) and (2) 1,2-Benzene dicarboxylic acid, 1,2-bis (2-Ethylhexyl) esters (DEHP). These compounds were reported in this plant for the first time. In comparison, CRH had % growth inhibition in the proliferation of MCF-7 cells up to 28.1%, with cancer cells A549, KB, KB-VIN, and MDA-MB-231 by >50% Compared to the negative DMSO of 0.20%, while the positive control could inhibit the growth of all cancer cells (100%). Our findings suggested that crude herb from the plant CRH was the potential for breast cancer treatment.

Monitoring of human dynamics by a flexible and comfortable polyvinylidene fluoride (PVDF) sensor

With the increasing demand for self-adaptive electronics, stretchable and conformable sensors with high sensitivity, stretchability, and self-adhesive are significant intelligent devices. Here a novel tactile sensor is demonstrated that maintains conformal contact to the object for efficient movement monitoring. The device, which was composed of the “H” well-manicured thermoplastic elastomer (TPE), a rectangular polyvinylidene fluoride (PVDF) film coupled with a silver electrode and clamped into the copper-clad signal line ends, and a “U” shaped super-elastic silica gel layer, provided satisfactory performance. The device was investigated as a dynamic monitoring sensor due to its stretchable and conformal configuration. The mechanical stability and high sensitivity suggested that, when attached to the skin of participants, the sensor detected motion induced strain which was experimentally demonstrated. The results show that the novel biomimetic sensor is effective in monitoring human dynamics, with an accuracy exceeding than 98.3%. The stretchable and conformable sensor is low-cost and nontoxic with potential applications in clinical, conformal detection, and artificial intelligence.

Development and Validation of HPLC And HPTLC for Simultaneous Analysis of E and Z Guggulsterone, A-11–KBA And 11–KBA from Herbal Formulation

RP-HPLC and HPTLC are two easy, sensitive, efficient, and accurate procedures that allow for simultaneous estimates of Z and E guggulsterone, A-11-KBA, and 11-KBA. For the HPLC method, we recommend the use of a symmetry C18 column. Using a solvent gradient based on solvent A (orthophosphoric acid) and solvent B (methanol), the effluent was monitored at 250 nm with a 1.0 mL/min flow rate. The peaks of 11-KBA and A-11-KBA were eluted at 5.8 and 6.3 minutes, while those of Z and E-guggulsterone were at 4.8 and 5.3 minutes. For the HPTLC method of separation, a silica gel layer was applied on an aluminum plate prewashed in methanol using a Camag Linomat V applicator fitted with a 100 μL syringe. The linear expansion was carried out using a solvent mixture of n-hexane, chloroform, ethyl acetate, and methanol (v/v/v: 10:3:3:1, respectively). Camag T.L.C. scanner III (V 1.4.3.6336), operating in reflectance-absorbance mode at 254 nm and controlled by win CATS software, was used to carry out the densitometric scanning. The R.F. resolutions for 11-KBA, A-11-KBA, E-guggulsterone, and Z-guggulsterone in the selected mobile phase were 0.68, 0.61, 0.39, and 0.28, respectively. The linearity, accuracy, and precision of the techniques were all confirmed. The proposed methods were successful in estimating E- and Z-guggulsterone as well as 11-KBA and A-11-KBA.

Effect on albumin and fibronectin adsorption of silver doping via ionic exchange of a silica-based bioactive glass

Protein adsorption is a crucial step in the life of biomaterials for bone application, such as bioactive glasses. The investigation of adsorption mechanisms is a difficult task per se, which is even more complex on bioactive glasses due to surface reactivity. Here, the effect of silver doping by ionic exchange on the interaction of a silica-based bioactive glass with albumin and fibronectin, serum proteins related to osseointegration, is reported. The presence of silver does not change relevant surface properties such as topography, surface energy, wettability, or surface ζ potential. Nevertheless, the interactions with proteins are much different. The presence of silver significantly increases the adsorption of albumin and fibronectin and leads to a higher loss of secondary structure compared to the undoped surface, as a consequence of the interactions and bonding between silver and thiols in the cysteine residues. Selectivity of silver-doped glass is discovered: Ag enhances more adsorption and denaturation of albumin since it has more cysteines than fibronectin. It is also here observed that due to the formation of a hydrated silica gel layer during adsorption, proteins are not only present on the surface of the bioactive glasses, but also embedded inside the surface reaction layer.

Fluorescence Spectroscopy and Silica Gel Applied as a Tool for Capture and Detection of Compressor Lubricant Oils

Here, we report the use of fluorescence spectroscopy for the identification of lubricant oils used in reciprocating compressors, and the use of silica gel as an adsorbent to capture lubricant oil vapors. The silica gel was tested for adsorption of lubricant oil vapors, by heating the samples at 200°C, the emission spectrum of the lubricant oils is observed on the silica gel layer, over 20 min of heating. The spectrum of the lubricant oils over the silica gel layer presents a redshift, an indication of the degradation effect. In order to investigate this effect on the optical properties, we conducted an experiment by heating the samples at (130 ± 4) °C, and collected at different times. The MID-infrared absorption of the samples presents bands of oxygen-containing groups at 1010 and 1050 cm-1, and NIR infrared absorption measurements at 3444 cm-1 show an increase in the hydroperoxide band during the degradation time. These two results indicate that the oxidation process is associated with the observed redshift of the absorption and emission bands in lubricant oils and over the adsorbent layer.

HPTLC-Bioluminescent Bioautography Screening of Herbal Teas for Adulteration with Hypolipidemic Drugs.

Teas based on nutraceutical herbs are an effective tool against hyperlipidemia. However, the adulteration with chemical drugs is frequently detected. By coupling bioluminescent bioautography with high performance thin-layer chromatography (HPTLC), we developed a facile method suitable for screening hypolipidemic drugs (ciprofibrate and bezafibrate) adulteration in five different herbal teas (lotus leaf, Apocynum, Ginkgo biloba, Gynostemia and chrysanthemum). First, the sensitivity of a bioluminescent bacteria to the analyte was evaluated on different HPTLC layer materials, revealing that the best performance was achieved on the silica gel layer. On this basis, sample extracts were separated on silica gel plates via a standardized HPTLC procedure, forming a selective detection window for the targeted compound. Then, the separation results were rapidly visualized by the bioluminescence inhibition of bacteria cells within 6 min after dipping. The observed inhibition displayed an acceptable limit of detection (<20 ng/zone or 2 mg/kg) and linearity (R2 ≥ 0.9279) within a wide concentration range (50-1000 ng/zone). Furthermore, the optimized method was performed with artificially adulterated samples and the recovery rates were determined to be within the range of 71% to 91%, bracing its practical reliability. Showing superiorly high simplicity, throughput and specificity, this work demonstrated that the analytical method jointly based on HPTLC and bioautography was an ideal tool for screening bioactive compounds in complex biological matrix.

Development and Validation of HPTLC Method for the Estimation of Escitalopram oxalate and Flupentixol Dihydrochloride in Pharmaceutical Formulation

A simple, precise, accurate High-performance thin-layer chromatography (HPTLC) method has been developed and validated for the estimation of escitalopram oxalate (ESC) and flupentixol dihydrochloride (FLU) in pharmaceutical formulation. Separation was achieved on an aluminum HPTLC plate coated with a 0.2 mm layer of silica gel 60 F254 with chloroform: methanol 4:6 (v/v) as mobile phase. The densitometry analysis was carried out in absorbance mode at 254 nm. The Rf values of escitalopram and flupentixol were 0.24 and 0.44 respectively. The linearity of the method was achieved in the range 3-7 µg/spot for ESC with correlation coefficient value 0.998 and 0.3-0.7µg/spot for FLU with correlation coefficient value 0.999. The developed method was validated according to ICH guidelines and the results were statistically validated. The limit of detection and quantification for escitalopram oxalate and flupentixol dihydrochloride was found to be 500 ng/spot and 50 ng/spot, 1000 ng/spot, and 100 ng/spot respectively.

КОМПОЗИЦИОННЫЕ МАТЕРИАЛЫ НА ОСНОВЕ АЛЮМОФТОРСИЛИКАТНОГО СТЕКЛА

The article presents the results of an analytical review of the literature on glass ionomer (glass polyalkenate) cements, which are widely used in dentistry. This materials consist from the powder and liquid, which form a plastic mass at mix that sets to form a solid. The composition of the powder and liquid components of glass ionomer cement has been analyzed. The solid component is powdered calcium or strontium aluminofluorosilicate glass, the liquid component is an aqueous solution of acrylic acid homopolymer or its copolymer with methylene-succinic acid, maleic acid and other monomers. Information about the range of compositions of aluminofluorosilicate glass, raw materials and melting process parameters are represented. An analysis of the curing mechanism of this dental material is also carried out. Acid-base interaction and cross-linking of polymeric acid molecules with ions extracted from glass occur at mixing the powder and liquid components. The final microstructure of the hardened glass ionomer cement is partially decomposed glass particles embedded in a matrix of calcium and aluminum polyalkenoates and coated with a layer of silica gel. The information presented in this review may be useful for a comprehensive understanding by dentists, developers of dental materials and scientific groups conducting research in this subject area of the physicochemical process of curing this material.

Development of reactive-transport models simulating the formation of a silica gel barrier under CO2 storage conditions

Geological storage of carbon dioxide (CO2) is a means of reducing greenhouse gas emissions. Key to the successful implementation of this technology is the ability to prevent CO2 leakage from the storage reservoir. One promising leakage abatement technology involves forming a geochemical barrier through reaction of an alkaline sodium silicate solution with CO2-enriched water or supercritical CO2. To investigate the feasibility of this technology at the field scale, three reactive-transport models were developed. The first simulations replicated previous laboratory studies (Castañeda-Herrera et al., 2018a), the second and third predicted the formation of a radial shield around the well and an impermeable silica gel layer serving as a flow diverter above the CO2 injection point. Good agreement with the experimental results was observed. Results also show the pH-dependent silica gel formation and its location deep in the reservoir strongly depend on the rate and the sequence of reagent injection as well as their efficient mixing in the reservoir. An alternative field application of the silica gel barrier is proposed to enhance capillary trapping beneath a lateral flow diverter. The application of silica gel barriers could make CO2 sequestration both safer and more efficient, enhancing further uptake of carbon capture and storage.

Macroscale Superlubricity of Black Phosphorus Quantum Dots

In the present work, Black Phosphorus Quantum Dots (BPQDs) were synthesized via sonication-assisted liquid-phase exfoliation. The average size of the BPQDs was 3.3 ± 0.85 nm. The BPQDs exhibited excellent dispersion stability in ultrapure water. Macroscale superlubricity was realized with the unmodified BPQDs on rough Si3N4/SiO2 interfaces. A minimum coefficient of friction (COF) of 0.0022 was achieved at the concentration of 0.015 wt%. In addition, the glycerol was introduced to promote the stability of the superlubricity state. The COF of the BPQDs-Glycerol aqueous solution (BGaq) was 83.75% lower than that of the Glycerol aqueous solution (Gaq). Based on the above analysis, the lubrication model was presented. The hydrogen-bonded network and silica gel layer were formed on the friction interface, which played a major role in the realization of macroscale superlubricity. In addition, the adsorption water layer could also prevent the worn surfaces from making contact with each other. Moreover, the synergistic effect between BPQDs and glycerol could significantly decrease the COF and maintain the superlubricity state. The findings theoretically support the realization of macroscale superlubricity with unmodified BPQDs as a water-based lubrication additive.

Design and Fabrication of Economical Industrial Air Filter

The design and fabrication of an economical air filter is for an industrial cupola furnace in MIDC, Hingna. The purpose of an industrial filter is to remove unburned coal particles’ hazardous fumes and reduce NOX in the environment. The filtration system consists of a filter box that comprises four filter media which are placed vertically like a cartridge. The first media is manufactured like a frame containing a steel wool scrubber. This frame traps hot gases and large particles of smoke. The second frame contains a layer of blue silica gel that absorbs moisture present in polluted air. The third filter frame consists of activated carbon which has chemical properties for the adsorption of Carbon dioxide and Nitrogen dioxide gases. The last filter is HEPA (high-efficiency particulate air) filter, which is made from element paper. It can filter 0.3μm diameter of dust particles. Finally, we get the filtered air through the exhaust. This filtration system is effective in terms of cost, cleaning, and maintenance. The filters are easy to remove when the dust gets chocked in it, also clean easily with the help of a pneumatic gun or some dust cleaning system. This will be economical and easy to maintain.

Thin-layer wicking experiments using magnetically treated water

Thin-layer wicking experiments were carried out using magnetically treated water and non-treated water. Two types of magnets of different constructions and strengths of the magnetic field (B = 15 mT and B = 0.27 T) were used. It was found that water circulating in the presence of a magnetic field penetrated faster into a porous layer of silica gel. This is reflected also in the changes in the electron donor and electron acceptor parameters of the surface free energy of the silica gel as calculated by using the Van Oss et al. approach. Based on this finding, it is hypothesized that changes in the water structure occur – that is, the water flow somehow destroys the network of hydrogen bonds in liquid water, while the magnetic field action promotes its formation.

Thin layer chromatography (TLC) analysis of Psoralea corylifolia leaf extract

Apart from the fact that key constituents of Psoralea corylifolia performed a wide spectrum of biological functions, the precise biological actions of the plant chemical constituents have remained elusive and just a few chemicals identified from this plant have been used for medication. With the medicinal properties of P corylifolia in mind, the present study was aimed to identify the fractions of the compounds of the leaves of this plant. A fast and simple procedure for the determination of the main active principle of medicinal plant is proposed. The extraction of active compounds was performed by means of three solvents based on a method of increasing polarity. The plant extract with known compositions was analysed on silica gel layers with the aid of three solvent systems. Different Rf values of the compound also reflected an idea about their polarity. The study will help in selection of appropriate solvent system for further separation of compounds from the plant extract.

Determination of active substances of the class of sulphonyl urea in matrixes

Goal. Selection of chromatographic method and development of a method for controlling the content of active substances nicosulfuron, rimsulfuron and thifensulfuron-methyl separately and in a combined presence in different combinations in matrices (formulations).&#x0D; Methods. The active substances were determined by thin layer chromatography (TLC). The linear range of the dependence of the area of the chromatographic zones on the amount of active substance was estimated by statistical methods using correlation-regression analysis.&#x0D; Results. Determination of pesticides includes the main stages: characterization of active substances by polarity; extraction their from the analyzed matrix; chromatographic separation, detection and quantification. The limiting integral indicator in the analysis is the dipole moment (µ, D), which characterizes the polarity of the compounds and their physicochemical properties. Nicosulfuron, rimsulfuron and thifensulfuron-methyl are low-polar compounds (2 &lt;µ ≤ 6, D) with dipole moments of 5.48; 5.30 and 5.28 D, respectively. Extraction of active substances is carried out with ethanol. Qualitative determination — in a thin layer of adsorbent silica gel in the mobile phase (hexane + chloroform + ethanol + ethanoic acid 30:10:5:1) and with a dielectric constant ε = 5.12. Compounds were identified under a chromatoscope (λ 254 nm) and using bromophenol blue developing reagent and subsequent bleaching of the chromatogram background with citric acid solution. The dependence of the area of the chromatographic zone of the compound (S, mm2) on its amount (C, µg) is linear in the detection range of 0.30—1.30 µg and is described by the regression equation for: thifensulfuron-methyl S = 25.057 C + 0.4367 (R2 = 1.00); nicosulfuron S = 22.272 C + 0.0532 (R2 = 1.00); rimsulfuron S = 17.519 C + 0.9456 (R2 = 1.00). The equations are used to quantify the active substances on the chromatogram.&#x0D; Conclusions. The use of TLC method allows to select selective conditions and to develop a method for determination of thifensulfuron-methyl, nicosulfuron and rimsulfuron in herbicide formulations separately and in combined presence in different combinations and quantities, which allows to determine three active substances in one analysis with high accuracy reproducibility (relative error, &lt;5% at n = 5, P = 0.95). The introduction of the developed and patented method makes it possible to determine the active substances of the sulfonylurea class in herbicide formulations by analytical and toxicological laboratories, testing services without the use of expensive devices.

Long-term stable, high accuracy, and visual detection platform for In-field analysis of nitrite in food based on colorimetric test paper and deep convolutional neural networks

Nitrite is one of the most common carcinogens in daily food. Its simple, rapid, inexpensive, and in-field measurement is important for food safety, based on the requirements of the standard from Codex Alimentarius Commission and China. Using polyacrylonitrile (PAN) and thin layer silica gel (SG), p-aminophenylcyclic acid (SA) and naphthalene ethylenediamine hydrochloride (NEH), as carriers and chromogenic agents, respectively, PAN-NSS as nitrite color sensor is proposed. After fixing and protecting of SA and NEH with layer-upon-layer PAN, the validity period of the test paper can be prolonged from 7 days to more than 30 days. The reproducibility of PAN-NSS preparation is ensured by electrospinning. Combined with PAN-NSS, deep convolutional neural network (DCNN) and APP as a visual monitoring platform, which has the functions of rapid sampling, data processing and transmission, intuitive feedback, etc., and provides a fully integrated detection system for field detection.

Simultaneous analysis of eprosartan and hydrochlorothiazide in tablet formulation by High- Performance thin layer chromatography with ultraviolet absorption densitometry

A new, simple, accurate, and precise high-performance thin-layer chromatographic method has been established for simultaneous analysis of Eprosartan and Hydrochlorothiazide from a tablet formulation. Standard and sample solutions of Eprosartan and Hydrochlorothiazide were applied to precoated 250 μm layer of silica gel G 60 F and the plates were developed with Chloroform: Acetonitrile: Glacial Acetic Acid (7:3:1,v/v/v) as mobile phase. Detection and evaluation of densitograms was performed densitometrically at 254 nm. The linear range was 200-700 ng/band with the retention factors of Eprosartan and Hydrochlorothiazide were 0.26± 0.02 and 0.44±0.02, respectively. The method was validated and successfully used for analysis of the drugs in tablets.

Development and validation of pimavanserin tartrate by normal phase- HPTLC method

For the determination of pimvanserin tartrate in bulk and formulation, a rapid and simple High Performance Thin Layer Chromatography at 226 nm was developed and validated. The determination was carried out on thin coated aluminum backing plates covered with 200 mm layer of silica gel G 60 F254 (10×10 cm) plate as stationary phase and using a mobile phase of methanol: chloroform: trimethylamine (4:6:0.1 v/v/v) respectively. With a correlation coefficient (r) of 0.998, the development of pimvanserin tartrate was linear in the range of 0.7 to 4.2 µg/ml. The limit of detection (LOD) was found to be 7.68 ng/spot while the limit of quantification was found to be 23.28 ng/spot. The percentage label claim of pimvanserin tartrate in bulk and formulation was found to be 99 – 101 %. The percentage found in the formulation shows that no effect of excipient on drug. The conducted procedure has the benefit of being simple and quick. As a result, it can be used to examine pimvanserin tartrate in pharmaceutical formulations.