Silica Plates Research Articles

DETERMINATION OF LAMOTRIGINE IN TABLETS USING HPTLC, HPLC, AND DERIVATIVE SPECTROPHOTOMETRY METHODS

The determination of lamotrigine in tablets using high-performance thin-layer chromatography (HPTLC), high-performance liquid chromatography (HPLC), as well as direct, first, second, and third derivative ultraviolet spectrophotometry methods are described. HPTLC method was performed using silica plates, a mobile phase composed of toluene:acetone:ammonia (3:7:0.5, v/v/v), and a densitometric detection at 312 nm. Moreover, quantification was achieved in the concentration range of 0.25–10.0 µg/spot and with good precision (RSD = 2.19%) and recovery (97.92%), using a nonlinear calibration curve by fitting to y = a + blnx. HPLC method was performed using a Luna C18 column and isocratic elution mode with a mobile phase composed of methanol: phosphate buffer (25:75, v/v) and delivered at a flow rate 1.2 mL/min. Proposed HPLC method provided good results of precision (RSD = 1.86%) and recovery (101.51%) in the concentration range of 0.25–7.5 µg/mL using linear y = a + bx regression analysis. For the UV-derivative spectrophotometry method, all derivatives and wavelengths studied proved accurate linearity, precision (RSD = 0.96–1.87%), and recovery (96.74–101.90%). Moreover, no interference was found from tablet excipients at the selected wavelength and assay procedures. The developed methods were found to be validated and showed good precision and reproducibility.

Separation and Identification of Antidepressant Drugs in Human Plasma by SPE-TLC Method

Development and validation of thin layer chromatography (TLC) and solid phase extraction (SPE) for the separation and identification of simple mixtures of antidepressant drugs (fluvoxamine maleate, paroxetine and sertraline) was achieved by using 2-propanol-dicloromethane(DCM) (70:30, v/v) at 30±1 ÂoC. R f values were 0.44, 0.22 and 0.68 for fluvoxamine maleate, paroxetine and sertraline, respectively on normal silica plates. The metal ions Fe(II), Ni(II), Cu(II) and Zn(II) of 0.1% concentration, were used to study their effect on the separation of the analytes under study. The R f values of these drugs on impregnated plates were in the range of 0.18 to 0.64. The separation of these drugs on plain and impregnated plates was compared and it was found that the best separation was on Ni(II) impregnated plate with compact spots. The limits of detection of these drugs were also calculated and found to be 0.1-0.2 ngmL -1 for both plain and impregnated plates. The values of the resolution data (R) for fluvoxamine maleate, paroxetine and sertraline were greater than 1.0 and, hence, complete separation. The solid phase extraction conditions of these dugs were phosphate buffer (50 mM, pH 9.0) with 0.10 mL min -1 as flow rate. The best eluting solvent was methanol containing 0.1% acetic acid for all anti-depressant; with 0.1 mLmin -1 flow rate. The percentage recoveries of fluvoxamine maleate, paroxetine and sertraline drugs were 41%, 35% and 33%, respectively. The values of standard deviation, correlation coefficient and confidence level for the TLC (R f ), SPE (percentage recovery) and UV-Visible spectrometric methods for fluvoxamine maleate, paroxetine and sertraline were in a range of ±0.14-0.33, 0.9992-0.9998 and 95.00-98.75% respectively.

Possible application of laser-induced backside dry etching technique for fabrication of SERS substrate surfaces

Laser-induced backside dry etching (LIBDE) method has proved to be capable of micro- and nanomachining of transparent materials. In present study the applicability of this technique was tested to prepare surface structures that are suitable for surface enhanced Raman scattering (SERS) spectroscopy. Fused silica plates were coated with 16nm thick silver layer by pulsed laser deposition (PLD) method. The metal absorbing film was irradiated and removed by 10 ArF excimer laser (λ=193nm, FWHM=20ns) pulses perpendicularly through the transparent samples at 1200mJ/cm2 fluence. The remaining part of the silver coating was dissolved chemically shortly after the experiment using nitric acid. After this the etched holes were re-coated with 10, 20 and 40nm thick silver layers by PLD, respectively. SERS activity of the different parts of the holes was investigated by a Thermo Scientific DXR Raman Microscope at 785nm wavelength using 10−3 M aqueous solution of Rhodamin 6G as reference sample. SERS spectra were recorded at different areas of the holes having various roughness parameters. It was found that the intensity of the main peaks depended significantly on the surface morphology of the tested area and the thickness of its silver coating.

The Effect of Aluminum in Solution on the Dissolution of Amorphous Silica and its Relation to Cementitious Systems

One of the most serious causes of degradation of concrete is the alkali–silica reaction. Amorphous silicates present in certain aggregates react with the alkaline pore solution of the concrete to form a gel, which absorbs water and swells, leading to the expansion of the concrete. It is known that the deleterious effects of ASR can be suppressed by the incorporation of supplementary cementitious materials in the concrete, but the mechanisms operating are not clear. In this article, we study a model system of amorphous silica plates in simulated pore solutions by X‐ray photoelectron spectroscopy (XPS), to demonstrate that aluminum in solution can directly suppress the dissolution of amorphous silica under the highly alkaline conditions found in concrete. XPS shows that aluminum species are incorporated into the framework of the silica structure. Scanning electron microscope (SEM) and atomic force microscope (AFM) images confirmed the reduction in dissolution of silica in solutions containing aluminum.

Senyawa Phenolik Akar Pisang CV. Kepok (Musa acuminata) yang Diinduksi dengan Fungi Mikoriza Arbuskular Indigenus PU10-Glomus sp 1 terhadap Penyakit Darah Bakteri

Cooking banana (Musa acuminata) cv. Kepok is the most susceptible to Blood disease bacterium (BDB) infection.From previous study revealed the best isolate indigenous Arbuscular Mycorrhiza Fungi-Pasar Usang 10 (PU10-Glomus sp 1) could induce cv.Kepok resistance to BDB in green house and field experiment. The AMF could changethe phenolic compound in root plant. This objectives were to measure the root phenolic compound and bioassayto BDB. The 50 grams fresh inoculant PU10-Glomus sp 1 were applicated to banana root plants 60 days old with 6levels time course: 12; 24; 36; 48; 72; 92 hours and control (without PU10-Glomus sp 1). The root methanolicextraction followed to Echeverri et al., (2002) methode with vacuum concentration of the filtrate and partitioninginto ethyl acetate revealed the presence of an antibacterial compound as detected by TLC (Thin LayerChromatography), assay phenolic contained by Spectrofotometer UV-Vis 1700. PharmaSpec. Shimadzu andbioassay using BDB. Nine antibacterial compounds rose from root banana seedling colonized by PU10-Glomus sp1 in 12 hours after applicated (haa) ; 24; 36 and 48 haa. They were with Rf values of 0.16; 0.17; 0.19; 0.26; 0.32; 0.37;0.71; 0.80 and 0.83 on silica plates run in hexane:ethyl acetate (1:2 v/v) and control contained only 0.05 and 0.28.These compounds produced fluorescens which was bright yellow green spots and purple and have antimicbrobialproperties to BDB.

Neutral lipid composition changes in the fat bodies of engorged females Rhipicephalus microplus ticks in response to fungal infections

The tick's fat body plays an essential role in energy storage and utilization. This study aimed to analyze the fat body neutral lipid composition in Rhipicephalus microplus engorged females. In the first study (physiological profile of untreated ticks), the lipid analysis took place over the course of 4 days; the engorged females were incubated at optimal conditions and their fat bodies were dissected daily. Fat body lipid analysis after fungal infection with Metarhizium anisopliae sensu lato (s.l.) or Beauveria bassiana s.l. was performed with four groups: one without any treatment, one that was inoculated with a solution of 0.1 % Tween 80 in water, and two groups that were inoculated with M. anisopliae or B. bassiana conidial suspensions. The fat bodies were dissected 24 and 48 h after infection. Lipid analysis was conducted by thin-layer chromatography on a silica plate. The results of the physiological profile showed that the amounts of triacylglycerol (TAG) and free cholesterol (CHO) decreased with time, whereas cholesterol ester (CHOE) increased on the second and fourth days. Following M. anisopliae or B. bassiana infection, there was an increase in the amount of CHO after 24 h, whereas the other lipid classes were not altered. M. anisopliae caused an increase in CHOE and TAG and a reduction in CHO at 48 h after infection; however, B. bassiana infection did not cause significant alterations in the concentrations of these lipids. M. anisopliae and B. bassiana infection changed the fat body metabolism of engorged female R. microplus ticks. This study provides the first report of changes in the neutral lipid composition of the R. microplus fat body.

Applications of Fresnel diffraction from the edge of a transparent plate in transmission

When a transparent plane-parallel plate is illuminated at the edge region by a quasi-monochromatic parallel beam of light, diffraction fringes appear on a plane perpendicular to the transmitted beam direction. The sharp change in the refractive index at the plate boundary imposes an abrupt change on the phase of the illuminating beam that leads to the Fresnel diffraction. The visibility of the diffraction fringes depends on the plate thickness, refractive index, light wavelength, and angle of incidence. In this report we show that, by recording the visibility repetition versus incident angle, one can measure the plate refractive index, its thickness, and light wavelength very accurately. It is also shown that the technique is indispensable for specifying color dispersion in plate shape samples. The technique is applied to the measurement of dispersion in a fused silica plate and the refractive indices of soda lime slides.

Interpreting atomic force microscopy measurements of hydrodynamic and surface forces with nonlinear parametric estimation

A nonlinear parameter estimation method has been developed to extract the separation-dependent surface force and cantilever spring constant from atomic force microscope data taken at different speeds for the interaction between a silica colloidal probe and plate in aqueous solution. The distinguishing feature of this approach is that it exploits information from the velocity dependence of the force-displacement data due to hydrodynamic interaction to provide an unbiased estimate of the functional form of the separation-dependent surface force. An assumed function for the surface force with unknown parameters is not required. In addition, the analysis also yields a consistent estimate of the in situ cantilever spring constant. In combination with data from static force measurements, this approach can further be used to quantify the extent of hydrodynamic slip.

Controlling spatial distribution of thermal poling induced second-order optical nonlinearity with multilayered structures

Fused silica plates with boron-doped silicate multilayered thin films are thermally poled to create second-order optical nonlinearity for nonlinear optical applications. Measurement results from second harmonic microscopy show that the spatial distribution of the induced nonlinearity peaks at the interfaces between different layers where there is an abrupt change in boron concentration. A simple model is suggested to simulate the nonlinearity-trapping effect at the interfaces. This nonlinearity-trapping effect is not restricted to interfaces with abrupt refractive index changes; results from silica plates with deposited multilayered pure silica thin films show that the interface between the silica substrate and the silica thin film also has the nonlinearity-trapping effect.

Radiative heat transfer between two dielectric nanogratings in the scattering approach

We present a theoretical study of radiative heat transfer between dielectric nanogratings in the scattering approach. As a comparision with these exact results, we also evaluate the domain of validity of Derjaguin's Proximity Approximation (PA). We consider a system of two corrugated silica plates with various grating geometries, separation distances, and lateral displacement of the plates with respect to one another. Numerical computations show that while the PA is a good approximation for aligned gratings, it cannot be used when the gratings are laterally displaced. We illustrate this by a thermal modulator device for nanosystems based on such a displacement.

Evaluation of CYP11Bs expression in HCT116 cells

CYP11B1 and CYP11B2 are enzymes respectlively responsible for cortisol and aldosterone biosynthesis. In human steroid biosynthesis, CYP11B1 converts 11-deoxycortisol to cortisol and CYP11B2 converts 11-deoxycorticosterone to aldosterone. In this study, we utilized methods cell culture (COS-1 and HCT116), transfection of vector pSVL, pSVL+11B1, pSVL+11B2 and coexpression of bAdx/hAdx into 2 cell culture. Steroids were extracted by using chloroform and separated on high performance thin layer chromatography (HPTLC) on silica plate. Results showed evaluation of CYP11Bs in HCT116 cells. The effect of electron transport protein of bovin adrenodoxin was better than electron transport protein of human adrenodoxin in HCT116 cells. Therefore, HCT116 cell could be used to study the metabolism of steroids by 2 isozyme CYP11Bs.

Aqueous CO2 Solutions at Silica Surfaces and within Nanopore Environments. Insights from Isobaric–Isothermal Molecular Dynamics

We present a detailed molecular-based characterization via isobaricisothermal molecular dynamics simulation of the microstructure and dynamics of water-rich aqueous CO2 solutions at silica surfaces and under extreme confinement between finite silica plates at state conditions relevant to geologic capture and sequestration of carbon dioxide. The study comprises three types of slit-pore plates to represent two extreme cases of surface polarity, and a mismatched pair of plates, to interrogate the fluid behavior at and confined between heterogeneous surfaces. We found layer formation of H2O and CO2 whose strength depends on the nature of the plate surface, i.e., stronger H2O layering at hydrophilic than at hydrophobic plates with a simultaneous weaker water mediated CO2 /hydrophilic-surface interactions. We observed the opposite behavior with the hydrophobic plates where the weaker water layering results from the CO2 mediated H2O/hydrophobicsurface interactions. Moreover, we illustrated how the interplay between these types of interactions and extreme fluid confinement, i.e., strong overlapping of interfacial structures, can induce a drying out of the pore environment whose immediate consequence is a significant CO2 concentration enhancement relative to that of the bulk environment. Finally, we assessed the effect of the nature of the plate surfaces on the translational diffusion coefficient of water,more » where we found that this property changes 2 monotonically at purely interfacial regions, but non-monotonically under confinement.« less

Electrochemically functional graphene nanostructure and layer-by-layer nanocomposite incorporating adsorption of electroactive methylene blue

This paper describes preparation and characterization of electrochemically functional graphene nanostructure incorporating adsorption of electroactive methylene blue (MB) dye onto graphene and nanocomposite assembled using layer-by-layer of graphene with MB on solid substrates. UV–visible spectroscopy, FT-IR spectroscopy, Raman spectroscopy and electrochemistry for systematical characterization of the MB adsorption onto graphene reveal the formation of a MB/graphene adsorptive nanostructure through π–π stacking and hydrophobic interactions. Compared with MB adsorbed onto a graphene oxide (GO) modified electrode and MB adsorbed onto a GC electrode, MB adsorbed onto a graphene modified electrode exhibits a good stability and distinct electrochemical properties. Additionally, MB adsorbed onto graphene can improve the water-disperse ability of graphene. Furthermore, scanning electron microscopy, UV–vis-NIR spectroscopy and electrochemistry demonstrated that directly layer-by-layer assembling of MB and graphene was an excellent route to prepare a functional nanocomposite on different solid substrates including silica plate, quartz slide and glassy carbon electrode. The excellent electroactivity and the high stability of electrochemically functional graphene nanostructure and the layered nanocomposite are envisaged to make them very useful electrochemically functional nanomaterials for practical development of electronic devices such as biosensors and photovoltaic cells.

TLC determination of triazinic pesticides from soils — A comparative study of some extraction methods

The triazines are the most widely used herbicides. Presenting high risks for human health, they must be determined in very different matrices and at low concentration level. This paper is focused on thin-layer chromatographic (TLC) determination of triazinic herbicides (atrazine, simazine, and propazine) from two types of soils (sandy category and peat). The TLC analyses were carried out on silica plates using multiple developments with toluene-acetone mixtures as mobile phase. Linear calibration curves were obtained in the range of 0.1–1 mg mL−1 with correlation coefficient R2 above 0.9855; limit of detection (LOD) and limit of quantification (LOQ) were below 0.7809 and 1.481 μg/spot, respectively. The analytes extraction was performed using four different techniques: magnetic stirring at room temperature, reflux, ultrasound assisted extraction and microwave assisted extraction. Methanol or methanol-water mixtures were selected as extracting solvent. Blank soil samples were spiked with triazines at 1 mg ...

Optimization of the resonant wave output coupling of a singly resonant optical parametric oscillator using an intracavity plate

We present a technique allowing us to optimize the output coupling of the resonant wave of a singly resonant optical parametric oscillator (SRO). By inserting a silica plate inside the cavity and tilting it around the Brewster angle, the output coupling of the SRO can be easily varied. This technique combines in principle the advantage of an efficient output coupling together with the possibility of controlling the frequency of the resonant wave of the SRO. We use this plate inside a 532-nm-pumped SRO to extract 1.6 W at 1.2 μm with a pump depletion of 80 %. We also show the possibility of determining the intracavity loss of the OPO, which is a useful parameter regarding its optimization.

Synthesis of Er-doped ZnO nanoparticle/organic hybrid from metal-organics

An Er-doped ZnO nanoparticle/organic hybrid was synthesized in situ from zinc acrylate (ZA) and erbium acetate (EA) using methylhydrazine. Nano-sized Er-doped ZnO particles were formed in an organic matrix by hydrolysis and polymerization of ZA–EA at 80 °C. The crystallinity of the Er-doped ZnO particles in the hybrid was dependent upon the hydrolysis temperature and water amount. Analysis by transmission electron microscopy and energy dispersive X-ray analyzer revealed that crystalline ZnO nanoparticles doped with Er were dispersed in the organic matrix. The hybrid film sandwiched between fused silica plates was highly transparent. The Er-doped ZnO particle/organic hybrid showed a photoluminescence peak at 0.81 eV (1.54 μm) attributed to the transition of Er3+ ions.

Influence of piezoceramic to fused silica plate thickness on the radii of curvature of piezoelectric bimorph mirror

Piezoelectric based bimorph mirrors (PBM) find extensive use in focusing of x-ray beams. Many optical instruments require use of PBM whose radii of curvature can be tuned precisely. The 100 mm and 300 mm PBMs were fabricated with varying piezoelectric to fused silica plate thicknesses. The radii of curvature of free standing mirrors were measured as a function of voltage and it was found to decrease with increasing voltage. For a given piezoelectric plate thickness, as the fused silica thickness increases, the radii of curvature was found to increase owing to increase in stiffness of the mirror. On the other hand, for a given fused silica plate thickness, when the piezoelectric plate thickness is increased, the radii of curvature are decreased for a given electric field, due to increase in generated force. This study brings out the influence of piezoceramic to fused silica plate thickness on the radii of curvature of PBM.

The PANDA 3D Disc DIRC

A 3D Disc DIRC detector is foreseen to provide particle identification in the endcap region of the PANDA experiment at the future FAIR facility. The 3D-DIRC is a synthesis of the previously proposed FL-DIRC and TOP-DIRC at PANDA. It is based on the measurement of the internally reflected Cherenkov light in a 2 cm thick fused silica plate. Position sensitive single photon detectors — either MCP-PMTs or a SiPMs — are placed in the focal plane of small focussing light guides and will provide a measurement of a projection of the Cherenkov angle. A precise determination of the time-of-propagation of the photons will allow to extract additional information of the Cherenkov angle and it will improve the identification of the signal pattern in a high luminosity, high background environment. Dichroic mirrors will be used to handle dispersion effects in the generation and propagation of the photons. The detector is expected to separate pions and kaons up to a momentum of ∼ 4 GeV/c.

Silica anchored fluorescent organosilicon polymers for explosives separation and detection

The luminescent organosilicon copolymers poly(silafluorenyldiethynylspirobifluorene) and poly(tetrasilolediethynylspirobifluorene) have been covalently linked to a silica gel thin layer chromatography (TLC) support through the use of a trimethoxysilyl end group. Surface functionalization of silica with the fluorescent sensing polymer allows for more efficient quenching by the analyte, due to the small amount of fluorophore present, thus yielding enhanced detection sensitivity. The attachment of the sensing polymers onto a chromatographic support also allows for simultaneous separation of an explosive mixture, and component identification through the use of multiple sensing polymers. In a 1.0 mm2 area solution spotted onto the fluorescent silica plate, detection limits obtained for the explosives TNT (2,4,6-trinitrotoluene), DNT (2,6-dinitrotoluene), PA (picric acid), Tetryl (N-methyl-N,2,4,6-tetranitroaniline), HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), RDX (1,3,5-trinitro-1,3,5-triazacyclohexane), and Cl-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane) ranged from 4 to 750 pg mm−2. Since less than 350 pg of highly fluorescent polymer is required to coat each TLC plate, the relatively small amounts of explosive being detected still represent an excess of quencher over sensing fluorophore.

Experimental research and application of pulse clean technique based on cross polarized wave generation

Cross polarized wave (XPW) generation technique is used to improve the contrast of the output pulses from a 800 nm Ti: sapphire femtosecond (fs) laser. The measured temporal contrast of the cleaned pulse is 1011 (limited by the dynamic range of the third-order auto-correlator), which is 3 orders of magnitude higher than the temporal contrast ratio of the initial pulse. The efficiency of XPW is 22%. And the bandwidth of the cleaned pulse is broadened after the XPW nonlinear process. Through the dispersion compensation using double chirped mirrors and fused silica plate, the 25 fs pulse duration is achieved. With the cleaned pulse used as the seed of a TW-level Ti: sapphire chirped-pulse amplification laser system, the 250 mJ/50 fs pulses corresponding to 5 TW peak power are obtained. And the 1011 temporal contrast is demonstrated on the time scale of hundreds of picoseconds before the main femtosecond pulse.