Physicochemical Study of the Adsorption of Oxprenolol Hydrochloride by Montmorillonite

The interaction between oxprenolol hydrochloride and montmorillonite was studied by adsorption isotherms, x-ray diffraction and i.r. spectroscopy.

The adsorption isotherm fits Langmuir's equation and the maximum amount of oxprenolol adsorbed by the clay is 70 mEq/100 g of clay.

The results of x-ray diffraction studies and i.r. spectroscopy reveal that the oxprenolol molecule is adsorbed into the interlayer space of the clay and that the mechanism of adsorption is cation exchange.     

Application of Methyl Cinnamate/Montmorillonite as Ultraviolet Radiation Shelters

Abstract

The interaction of methyl cinnamate/montmorillonite samples prepared by melting the former onto the second or by joint grinding, has been studied by x-ray diffraction. differential thermal analysis, thermogravimetric analysis and Fourier-transform infrared spectroscopy. Formation of an interlayer compound has been observed, leading to an increase of 4.15 or 3.42 A (samples obtained by melting or grinding, respectively) in the basal spacing of the clay. Formation of such a complex leads to a displacement of molecular water from the interlayer space, as concluded from the thermal studies. No chemical change is observed in the methyl cinnamate molecule, as confirmed by infrared spectroscopy. The system prepared improve the shelter properties of the clay and the drug separately, mainly in the C zone of the ultraviolet spectrum (290-190 nm).     

In Vitro Adsorption-Desorption of Papaverine Hydrochloride by Montmorillonite

Abstract

In an attempt to obtain the basic data necessary in research into the possible use of papaverine in sustained action formulas in the form of complexes with Montmorillonite, the “in vitro” adsorption and desorption of the drug as a function of different factor was studied.

The study of the interaction and adsorption mechanisms was carried out by adsorption isotherms, X-ray diffraction and I.R. spectroscopy.

The adsorption of papaverine by Montmorillonite increases with the rise in pH of the solution, within the pH range studied (2-4) in agreement with the solubility of the compound. According to the isotherms, adsorption increases with the concentration of the solution up to 79.16 mEq/100 g (very close to the exchange capacity of the clay). The data fulfill Langmuir's equation, implying a chemical adsorption mechanism.

The results of the X-ray diffraction and I.R. spectroscopy studies confirm the intercalation of the organic cation into the interlayer space of montmorillonite, forming a complex of defined spacing (17.66 Å (DL = 8.06 Å)). The studies revealed that cation exchange is the mechanism responsible for this interaction.

The “in vitro” desorption studies showed that the amount of papaverine desorbed from the complex depends on the pH of the solution, on its ionic strength, on the presence of free drug and on the elimination rate of the desorbed complex; in all cases, desorption was seen to be very low.

In general, release of the drug follows a single first order kinetic process with a rapid initial desorption of the drug.     

Determination of the surface area of mesoporous silicates by X-ray diffraction patterns using partial least squares and multiple linear regressions

ABSTRACT

Surface area of modified mesoporous silicates have been quantitatively determined using x-ray diffraction patterns and chemometric methods. The modified mesoporous silicate samples with varying surface area (223–1164 m²/g) were synthesized and their effective surface areas were calculated by the Brunauer–Emmett–Teller (BET) method using their nitrogen adsorption isotherms. The x-ray diffraction patterns of the samples were measured. The chemometric techniques were used to model the diffraction patterns as a function of the calculated surface area. The prediction results of the multiple linear regression (MLR) model was better than the partial least squares (PLS) model and both of the methods can be used for predicting the surface area of new mesoporous samples.     

Synthesis,characterization and properties of polyaniline/expanded vermiculite intercalated nanocomposite

Abstract

The synthesis characterization and conductivities of polyaniline/expanded vermiculite intercalated nanocomposite are presented in this paper. The conductive emeraldine salt form of polyaniline is inserted into the interlayer of expanded vermiculite to produce the nanocomposite with high conductivity. The structures and properties are characterized by transmission electron microscopy x-ray diffraction spectroscopy fourier transform infrared spectroscopy thermogravimetry analysis and by the measurements of conductivity and stability. The results show that an intercalated nanocomposite with high conductivity and stability is obtained. The synthesis conditions are optimized to obtain the highest conductivity which is 6.80 S cm^?1.     

Optimization of growth conditions of ZnO nano thin films by chemical double dip technique

Abstract

Zinc oxide (ZnO) nano thin films have been deposited by the chemical double-dip technique using aqueous ZnSO₄ and NaOH solutions. The ZnO films were characterized in terms of surface morphology by x-ray diffraction, energy-dispersive x-ray analysis (EDX), the use of a scanning electron microscope (SEM) and atomic force microscope (AFM) for surface morphology. The films exhibited a smooth morphology. The chemical states of oxygen and zinc in the ZnO nano thin films were also investigated by x-ray photoelectron spectroscopy (XPS). In the present investigations, highly textured ZnO thin films with a preferential (002)-orientation were prepared on glass substrates. The deposition conditions were optimized to obtain device-quality films for practical applications.     

Functionalized diatom silica microparticles for removal of mercury ions

Abstract

Diatom silica microparticles were chemically modified with self-assembled monolayers of 3-mercaptopropyl-trimethoxysilane (MPTMS), 3-aminopropyl-trimethoxysilane (APTES) and n-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (AEAPTMS), and their application for the adsorption of mercury ions (Hg(II)) is demonstrated. Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy analyses revealed that the functional groups (–SH or –NH₂) were successfully grafted onto the diatom silica surface. The kinetics and efficiency of Hg(II) adsorption were markedly improved by the chemical functionalization of diatom microparticles. The relationship among the type of functional groups, pH and adsorption efficiency of mercury ions was established. The Hg(II) adsorption reached equilibrium within 60 min with maximum adsorption capacities of 185.2, 131.7 and 169.5 mg g^?1 for particles functionalized with MPTMS, APTES and AEAPTMS, respectively. The adsorption behavior followed a pseudo-second-order reaction model and Langmuirian isotherm. These results show that mercapto- or amino-functionalized diatom microparticles are promising natural, cost-effective and environmentally benign adsorbents suitable for the removal of mercury ions from aqueous solutions.     

Development and characterization of clay facial mask containing turmeric extract solid dispersion

Objective: To develop clay facial mask containing turmeric extract solid dispersion (TESD) for enhancing curcumin water solubility and permeability and to determine suitable clay based facial mask.

Methods: The TESD were prepared by solvent and melting solvent method with various TE to polyvinylpyrrolidone (PVP) K30 mass ratios. The physicochemical properties, water solubility, and permeability were examined. The effects of clay types on physical stability of TESD, water adsorption, and curcumin adsorption capacity were evaluated.

Results: The TESD prepared by solvent method with a TE to PVP K30 mass ratio of 1:2 showed physically stable, dry powders, when mixed with clay. When TESD was dissolved in water, the obtained TESD micelles showed spherical shape with mean size of ～100?nm resulting in a substantial enhancement of curcumin water solubility,?～5?mg/ml. Bentonite (Bent) and mica (M) showed the highest water adsorption capacity. The TESD’s color was altered when mixed with Bent, titanium dioxide (TiO₂) and zinc oxide (ZnO) indicating curcumin instability. Talcum (Talc) showed the greatest curcumin adsorption followed by M and kaolin (K), respectively. Consequently, in vitro permeation studies of the TESD mixed with Talc showed lowest curcumin permeation, while TESD mixed with M or K showed similar permeation profile as free TESD solutions. The developed TESD-based clay facial mask showed lower curcumin permeation as compared to those formulations with Tween 80.

Conclusion: The water solubility and permeability of curcumin in clay based facial mask could be improved using solid dispersion technique and suitable clay base composed of K, M, and Talc.     

Factors Influencing Polymorphic Transition of Hyoscine N-Butyl Bromide

Abstract

Two crystalline forms of hyoscine N-butyl bromide (HBB) were identified and characterized by DSC, x-ray powder diffraction, scanning electron microscope and i.r. spectrophotometry techniques. DSC was the most useful method in differentiating the two polymorphs. The stable and metastable forms of HBB showed no significant variation in their x-ray and i.r. spectra. Melting points were 123.4 ± .5° and 143.6 ± .9° for the metastable and the stable forms respectively. Their purities exceeded 99% and their heat of fusion was obtained. While crystallization from methanol produced the metastable form, other solvents precipitated the stable form. Compression force transfered the metastable form into the stable form. Such transfere depended on the applied pressure. Mild trituration and ball milling had a negligible effect on crystalline transitions. Although storage at room temperature and at 55° converted the drug into its stable form, the two crystalline forms coexisted in the commercial samples of the same batch or different batches.     

Reusable hydroxyapatite nanocrystal sensors for protein adsorption

Abstract

The repeatability of the adsorption and removal of fibrinogen and fetal bovine serum on hydroxyapatite (HAp) nanocrystal sensors was investigated by Fourier transform infrared (FTIR) spectroscopy and quartz crystal microbalance with dissipation (QCM-D) monitoring technique. The HAp nanocrystals were coated on a gold-coated quartz sensor by electrophoretic deposition. Proteins adsorbed on the HAp sensors were removed by (i) ammonia/hydrogen peroxide mixture (APM), (ii) ultraviolet light (UV), (iii) UV/APM, (iv) APM/UV and (v) sodium dodecyl sulfate (SDS) treatments. FTIR spectra of the reused surfaces revealed that the APM and SDS treatments left peptide fragments or the proteins adsorbed on the surfaces, whereas the other methods successfully removed the proteins. The QCM-D measurements indicated that in the removal treatments, fibrinogen was slowly adsorbed in the first cycle because of the change in surface wettability revealed by contact angle measurements. The SDS treatment was not effective in removing proteins. The APM or UV treatment decreased the frequency shifts for the reused HAp sensors. The UV/APM treatment did not induce the frequency shifts but decreased the dissipation shifts. Therefore, we conclude that the APM/UV treatment is the most useful method for reproducing protein adsorption behavior on HAp sensors.     

Oral controlled drug delivery systems based on microporous polymers

Abstract

Microporous polypropylene (PP) powder shows excellent properties for tabletting. Oral controlled release delivery systems were made by simply blending with drug and compressing to make both matrix and coated tablets. To prevent wetting problems and food interactions, sodium lauryl sulphate (SLS) was adsorbed prior to tabletting on the surface of the microporous PP. In order to reveal possible dosage form-food interactions a new and simple food interaction model (slight modification of the USP XX paddle method) is proposed to standardize both in vitro and in vivo testing procedures. The PP coated oxprenolol tablets show no food interactions when tested in vitro in the food simulation mixture. The same liquid food was used in the in vivo study. The PP coated oxprenolol tablets were given to six male volunteers with and without the food. The absorption profiles, which were calculated by numerical deconvolution, showed hardly any food interactions in vivo. The absolute bioavailability at 12 hours was 38±19% on an empty stomach and 37±20 for the food experiment. The developed coated tablets are able to control the release of oxprenolol at least 12 hours both with and without concomitant food intake. Their bioavailability is comparable to different OROS formulations of oxprenolol controlled release systems based on microporous PP are not only highly effective ones but also low cost formulation products.     

X-ray diffraction measurements in high magnetic fields and at high temperatures

Abstract

A system was developed measuring x-ray powder diffraction in high magnetic fields up to 5 T and at temperatures from 283 to 473 K. The stability of the temperature is within 1 K over 6 h. In order to examine the ability of the system, the high-field x-ray diffraction measurements were carried out for Si and a Ni-based ferromagnetic shape-memory alloy. The results show that the x-ray powder diffraction measurements in high magnetic fields and at high temperatures are useful for materials research.     

Effects of SO2 on selective catalytic reduction of NO with NH3 over a TiO2 photocatalyst

Abstract

The effect of SO₂ gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH₃) over a TiO₂ photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO₂ (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO₂ gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N₂ adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst.     

On the unusual mechanism of Lewis acidity manifestation in HZSM-5 zeolites

The adsorption of CD₃CN and NH₃ on HZSM-5 zeolites containing prechemisorbed olefins were studied using diffuse reflectance i.r. spectroscopy. It is shown that in the presence of strong bases the unusual manifestation of Lewis acidity in these zeolites takes place as a result of fission of the Al←O bond in bridged alkoxyl groups by adsorbed base molecules. Nonempirical quantum-chemical calculations confirm this experimental finding and define the requirements of such Lewis acidity generation.     

Adsorption of carbon dioxide and methane on nanosized sodalite octahydrate zeolite

Nanosized sodalite octahydrate zeolite has been developed using a crystallization room temperature in the absence of organic templates. The best aging time found was 120?h and in this time the nanosized sodalite octahydrate zeolite is formed. The samples were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-Transform Infrared (FTIR) spectroscopy, x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and N₂ adsorption–desorption isotherm. The equilibrium adsorption capacities of pure gases CO₂ and CH₄ were measured at 298 and 308?K up to 20?bar on both powder and granules of sodalite octahydrate zeolite. With increasing temperature, the adsorption capacity decreases for both sodalite octahydrate zeolite powder and granules. The selectivity of CO₂ at 308?K over CH₄ was 6.53.     

Preparation and properties of antibacterial TiO2@C/Ag core–shell composite

Abstract

An environment-friendly hydrothermal method was used to prepare TiO₂@C core–shell composite using TiO₂ as core and sucrose as carbon source. TiO₂@C served as a support for the immobilization of Ag by impregnation in silver nitrate aqueous solution. The chemical structures and morphologies of TiO₂@C and TiO₂@C/Ag composite were characterized by x-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, energy dispersive x-ray spectroscopy and Brunauer–Emmett–Teller (BET) analysis. The antibacterial properties of the TiO₂@C/Ag core–shell composite against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were examined by the viable cell counting method. The results indicate that silver supported on the surface of TiO₂@C shows excellent antibacterial activity.     

Textural,structural and electrical properties of TiO2 nanoparticles using Brij 35 and P123 as surfactants

Abstract

The effect of the use of the triblock copolymer Pluronic P123[(PEO)₂₀(PPO)₇₀(PEO)₂₀, Aldrich] and the non-ionic polyoxyethylene-lauryl ether Brij 35 as surfactants on the textural, structural and electrical properties of nanosized TiO₂ is analyzed in this work. The as-obtained samples were thermally treated at 400 °C to eliminate the surfactant, promote dehydroxylation and crystallize the sample. The TiO₂ samples were characterized by thermal analysis, N₂ physisorption, x-ray diffraction analysis, micro-Raman spectroscopy and scanning electron microscopy. To evaluate the TiO₂ electrical features, I–V data were obtained. The x-ray diffraction results show that in the chemical synthesis using surfactants, the crystallite size is smaller than that of the commercial sample. The Raman spectroscopy results clearly indicate that, when P123 is used, the anatase phase of TiO₂ is obtained, whereas when Brij 35 is used a mixture of the anatase and brookite phases is obtained. The specific surface area and crystallite size of the TiO₂ prepared as indicated above are higher and smaller, respectively, than the corresponding properties found in commercial TiO₂. The I–V plot showed a nonlinear behavior of the nanosized TiO₂. The samples obtained with P123 showed the best electrical conductivity.     

Spectral Methods for Determination of Water

Abstract

Techniques based on the interaction of electromagnetic radiation with materials can be extremely useful for the characterization of water in solids of pharmaceutical interest. When combined with other physical methods, such as calorimetry, thermogravimetry, or titration, spectral techniques can be used to deduce information regarding the nature of water contained within a solid. The spectral methods are particularly useful in the study of hydrate species, and in the differentiation of hydrate water from entrapped or adventitious water. The most useful methods are powder x-ray diffraction, fourier transform infrared spectroscopy, and solid state nuclear magnetic resonance spectroscopy. These particular methods have been used in the study of ampicillin hydrate species.     

Block-copolymer-assisted synthesis of hydroxyapatite nanoparticles with high surface area and uniform size

Abstract

We report the synthesis of hydroxyapatite nanoparticles (HANPs) by the coprecipitation method using calcium D-gluconate and potassium hydrogen phosphate as the sources of calcium and phosphate ions, respectively, and the triblock copolymer F127 as a stabilizer. The HANPs were characterized using scanning electron microscopy, x-ray diffraction, and nitrogen adsorption/desorption isotherms. Removal of F127 by solvent extraction or calcination alters the structure of HANPs. The solvent-extracted HANPs were single crystals with their 〈001〉 axis oriented along the rod axis of the HANP, whereas the calcined HANPs contained two crystal phases that resulted in a spherical morphology. The calcined HANPs had much higher surface area (127 m² g^?1) than the solvent-extracted HANPs (44 m² g^?1).     

Compatibility study between oxprenolol hydrochloride and tablet excipients using differential scanning calorimetry

Abstract

Differential scanning calorimetry (DSC) was used to investigate the physico-chemical compatibility between oxprenolol hydrochloride and a number of commonly used tablet and capsule excipients.

Oxprenolol hydrochloride was found to be compatible with starch, Sta-Rx 1500®, Primojel®, Avicel PH 101®, Ac-Di-Sol® and cross-linked PVP. Interactions of oxprenolol hydrochloride with PVP, lactose and the lubricants magnesium stearate and stearic acid were found, although it cannot be conclusively stated that interaction incompatibilities will occur during storage at room temperature.