Evaluation of Batch-To-Batch and Manufacturer-To-Manufacturer Variability in the Physical Properties of Talc and Stearic Acid

Abstract

Magnesium stearate, talc and stearic acid are commonly used as lubricants in tablet formulations. Many studies on the batch-to-batch and manufacturer-to-manufacturer variability in the physical properties and lubricity of magnesium stearate have been reported in the literature. However, very few similar studies have been reported on talc or stearic acid. In this study, physical properties such as particle size, specific surface area, thermal behavior, moisture content, density, and particle shape and morphology of talc and stearic acid batches obtained from several manufacturers were examined. There was little batch-to-batch variability observed in the talc and stearic acid batches obtained from various manufacturers; however, differences in the particle size and specific surface area were seen in the two types of talc, USP samples obtained from one manufacturer. The scanning electron microscope photomicrographs of the stearic acid samples obtained from various manufacturers also showed some differences in the amount of flakes attached to the spherical particles.     

The Effect of the Variability in the Physical and Chemical Properties of Magnesium Stearate on the Properties of Compressed Tablets

Abstract

A series of magnesium stearate samples, supplied by foreign and domestic manufacturers, were characterized by their physical and chemical properties. The results Indicated that the samples differed significantly with respect to chemical purity, particle size and surface area. The properties of magnesium stearate lots, manufactured by the same company, were very similar. Whatever variation that was seen was principally due to different suppliers.

Microcrystall1ne cellulose tablet formulations were prepared and evaluated using samples of magnesium stearate obtained from 16 sources. Differences 1n tablet quality were observed 1n regard to bulk volume of the blends, tablet tensile strength, and tablet friability. The data revealed that the smaller particle sized magnesium stearate samples (2.4–7.0 μm), with a large surface area (10.6–14.8 m2/g), had the most detrimental effects on the physical properties of mlcrocrystalHne cellulose tablets. Regression analysis and modeling was used to define quantltate, and predict the effects of magnesium stearate source variation on the physical properties of mlcrocrystalHne cellulose blends and compressed tablets.     

Low temperature synthesis of nanocrystalline magnesium aluminate with high surface area by surfactant assisted precipitation method: Effect of preparation conditions

A surfactant assisted co-precipitation method was employed for the low temperature synthesis of magnesium aluminate spinel with nanocrystalline size and high specific surface area. Pluronic P123 triblock copolymer and ammonia solution were used as surfactant and precipitation agent, respectively. The prepared samples were characterized by thermal gravimetric and differential thermal gravimetric analyses (TG/DTG), X-ray diffraction (XRD), N₂ adsorption (BET) and transmission electron microscopy (TEM) techniques. The effects of several process parameters such as refluxing temperature, refluxing time, pH, P123 to metals mole ratio (P123/metals) and calcination temperature on the structural properties of the samples were investigated. The obtained results showed that, among the process parameters pH and refluxing temperature have a significant effect on the structural properties of samples. The results revealed that increase in pH from 9.5 to 11 and refluxing temperature from 40 °C to 80 °C increased the specific surface area of prepared samples in the range of 157–188 m² g^?1 and 162–184 m² g^?1, respectively. The XRD analysis showed the single-phase MgAl₂O₄ was formed at 700 °C.     

Evaluation of Particle Size Distribution and Specific Surface Area of Magnesium Stearate

The geometric mean diameter and several other particle size distribution parameters of nine lots of magnesium stearate from Mallinckrodt Inc. and one lot from Witco Corporation were determined using a light scattering particle size analyzer. Similarly, the specific surface area of these lots was also determined using both single and multi-point B.E.T. methods. A regression analysis of the data indicated that there was a good correlation between the specific surface area and the geometric mean diameter of the various samples. Also, the volume mean diameter, the sauter mean diameter, the 10th, 50th and 90th percentile points, and the span values were consistent with the geometric mean diameter data. The results of this study indicate that the use of a light scattering particle size analyzer provides a quick, simple and reliable technique for evaluating the batch-to-batch variability in magnesium stearate.     

Evaluation of Batch-To-Batch and Manufacturer-To-Manufacturer Variability in the Physical Properties of Talc and Stearic Acid

Magnesium stearate, talc and stearic acid are commonly used as lubricants in tablet formulations. Many studies on the batch-to-batch and manufacturer-to-manufacturer variability in the physical properties and lubricity of magnesium stearate have been reported in the literature. However, very few similar studies have been reported on talc or stearic acid. In this study, physical properties such as particle size, specific surface area, thermal behavior, moisture content, density, and particle shape and morphology of talc and stearic acid batches obtained from several manufacturers were examined. There was little batch-to-batch variability observed in the talc and stearic acid batches obtained from various manufacturers; however, differences in the particle size and specific surface area were seen in the two types of talc, USP samples obtained from one manufacturer. The scanning electron microscope photomicrographs of the stearic acid samples obtained from various manufacturers also showed some differences in the amount of flakes attached to the spherical particles.     

The Effect of the Variability in the Physical and Chemical Properties of Magnesium Stearate on the Properties of Compressed Tablets

A series of magnesium stearate samples, supplied by foreign and domestic manufacturers, were characterized by their physical and chemical properties. The results Indicated that the samples differed significantly with respect to chemical purity, particle size and surface area. The properties of magnesium stearate lots, manufactured by the same company, were very similar. Whatever variation that was seen was principally due to different suppliers.

Microcrystall1ne cellulose tablet formulations were prepared and evaluated using samples of magnesium stearate obtained from 16 sources. Differences 1n tablet quality were observed 1n regard to bulk volume of the blends, tablet tensile strength, and tablet friability. The data revealed that the smaller particle sized magnesium stearate samples (2.4-7.0 μm), with a large surface area (10.6-14.8 m2/g), had the most detrimental effects on the physical properties of mlcrocrystalHne cellulose tablets. Regression analysis and modeling was used to define quantltate, and predict the effects of magnesium stearate source variation on the physical properties of mlcrocrystalHne cellulose blends and compressed tablets.     

Degassing of magnesium alloy by rotating impeller degasser: Part 1 – Mathematical modelling

Abstract

A mathematical model was used to simulate the removal of hydrogen from magnesium alloy by a rotary impeller. It has been shown that the degassing efficiency is mainly dependent on the total surface area of the inert gas bubbles that is related to the rotation speed and the gas flowrate as well as the design of the impeller. An oxygen/water system was used to determine the total surface area of the inert gas bubbles experimentally. Finally, degassing experiments were carried out on magnesium melt to verify the mathematical model. Excellent agreement was obtained between the model predicted and the measured degassing efficiency. It was concluded that this model and the oxygen/water system are suitable to predicate the removal of hydrogen from magnesium alloy by the rotary impeller, and are also useful to the design of the impeller and the research of the effect of the processing parameters.     

The Effect of the Specific Surface Area of Heavy Magnesium Carbonate on its Tableting Properties

Abstract

Heavy magnesium carbonates, either granules or spray dried powders were prepared at five different temperatures respectively. It has been found that the specific surface area of the magnesium carbonates prepared at lower temperatures is higher than that prepared at higher temperatures. The moisture adsorption (%) of magnesium carbonates and the crushing strength of the magnesium carbonate compacts prepared at five pressure ranges showed linear relationships with the specific surface area of the magnesium carbonates. However, Heckel plots indicated that magnesium carbonates prepared at higher temperatures were more compressible.     

Structure and texture of heat-treated lithium borosilicate xerogel

Monolithic and transparent lithium borosilicate gels were obtained by using a cationic surfactant. The textural and structural properties of the pyrolysed xerogel at different temperatures were studied by IR, DTA–TG, X-ray, SEM and BET techniques. The obtained results show that the samples remain amorphous and mesoporous when the samples were heat treated below 600 °C. It is interesting to notice that Li⁺ does not establish a bond with the borosilicate network in this range temperature. Above this temperature, the crystallinity starts associated with the largest decreases of specific surface area and pore volume.     

Adsorption characteristics of activated carbon prepared from spent ground coffee

This paper reports results of a research project which attempts to produce low-cost activated carbon from agro-residue wastes. The ground coffee residue which is a by-product of coffee making was collected from coffee shops, prepared, and converted to activated carbon by a chemical activation method. The objective of this work is to investigate the effects of preparation conditions on properties of the activated carbon obtained. The preparation condition is defined by pyrolysis rate, concentration of ZnCl₂, impregnation time, and carbonization temperature. The pyrolysis rate was fixed at 10 °C min^?1 for 4 h with three concentrations of ZnCl₂ (5, 10, and 15 wt%), three durations of impregnation time (8, 12, and 24 h), and three carbonization temperatures (400, 450, and 500 °C). The morphology and specific surface area were, respectively, determined using SEM and BET techniques. It was found in this study that the activated carbon with the best properties was obtained at the preparation condition given by 15 wt% of ZnCl₂, impregnation time of 24 h, and 500 °C carbonization temperature. On average, the activated carbon had a pore diameter of 0.61 nm, specific surface area of 831 m² g^?1, and a total pore volume of 0.44 cm³ g^?1. It was also found that the adsorption isotherm of Cu (II) fitted well with Freundlich isotherm.     

Influence of the Physicochemical Variability of Magnesium Stearate on Its Lubricant Properties: Possible Solutions

Abstract

The variability of the physicochemical properties of 13 commercial batches of magnesium stearate (from three vendors) were determined using various physicochemical tests. Differences observed were related to the crystal lattice and the hydration state of the samples as well as the impurities contained in their matrices. A formulation model containing 2% of magnesium stearate was used to determine the lubricant properties of 6 of the 13 magnesium stearate lots received. The tablet press used was a Stoks® Single Station Instrumented F Press. The different lubricant properties observed were related to the particle size of the magnesium stearate lot used. The influence of the crystalline structure on the lubricant properties of magnesium stearate was also shown whereas the influence of the adsorbed water did not appear to determine process capabilities. Two possible solutions were evaluated to reduce the lubricant property differences among the lots tested. By decreasing the particle size of a lot of magnesium stearate, it has been possible to significantly improve its lubricant properties. Magnesium stearate in association with talc also presented an improvement of its lubricant properties.     

Investigation of Cs(I) and Sr(II) removal using nanoporous bentonite

ABSTRACT

Bentonites are types of clays made up the dominant constituent of montmorillonite. Four types of nano-porous and nano-structured commercial bentonite clays were studied in detail for their physicochemical and mineralogical properties vs. Cs and Sr adsorption. The instrumental analyses to study samples were X-ray diffraction (XRD), X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET) surface area measurements, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and thermogravimetry (TG). The XRF and peaks of XRD patterns at 2θ?=?8, 19.9, 35, 55, and 62 clearly indicated that the main component of the bentonite samples was montmorillonite. The BET analysis showed that B1 has the highest specific surface area among the other samples which its single and multiple point BET surface area were equal to 84.85 and 85.94?m²?g^?1, respectively. These values represents the amount of montmorillonite and adsorption capacity of samples. The physicochemical, structural and morphological characteristics of different samples were investigated through instrumental analysis. The results of separation processes of Cs(I) and Sr(II) showed 59.75 and 45.5% adsorption capacities for B3 and B2 which were the highest values among the others. The results lead to the conclusion that samples B3 had a good adsorption capacity to remove Cs(I) and Sr(II).     

Particle size effect of raw material on the pore structure of carbon support and its adsorption capability

In this study, a series of activated carbons were prepared from Tuncbilek lignite with different particle size by chemical activation. The effect of particle size of lignite on the pore structure of activated carbon and the adsorption kinetics of crystal violet (CV) onto these activated carbons was investigated. BET surface area values of activated carbon samples were determined in the range of 940–1054 m² g^?1. Adsorption capacity of CV onto activated carbons was investigated in a batch system by considering the effects of various parameters such as initial dye concentration, agitation time and adsorption temperature. The Langmuir and Freundlich isotherms were used to describe the adsorption equilibrium studies. The adsorption kinetics of CV has been discussed using the pseudo-first-order, pseudo-second-order and intraparticle diffusion models. Results show that the pseudo-second-order kinetic equation could describe the adsorption kinetics for CV onto activated carbons. Using the thermodynamic equilibrium coefficient obtained at different temperatures and for the initial dye, the thermodynamic constants of adsorption (ΔG°, ΔH° and ΔS°) were also evaluated.     

MEASUREMENT OF THE SPECIFIC SURFACE AREA OF POWDERS BY THIN LAYER WICKING

ABSTRACT

The specific surface areas (A) of different clay mineral powders were measured by both the BET method and by thin layer wicking. The values of A for the BET and the wicking experiments coincided within a few percent. Thus, the simple and inexpensive thin layer wicking approach may well suffice to obtain reliable specific surface area values for most powders. From the wicking data it is also possible to obtain a rough estimate of the average particle size.     

Mesoporous carbon spheres produced by hydrothermal carbonization from rice husk: Optimization,characterization and hydrogen storage

In this study, carbon spheres were synthesized from rice husk with hydrothermal carbonization method at different temperatures and different reaction times. Surface areas and pore size distributions of carbon spheres were characterized by BET surface area device, sphere morphology by SEM, structural characterization by FTIR-ATR and XRD, and thermal properties and degradation mechanism by DTA/TG. In addition, hydrogen gas adsorption measurements of the samples were also carried out with the Hiden IMI PSI gas storage device. It can be said that the required temperature is 280 °C and the required reaction time is 6 h in order to obtain homogeneous and ideal sphere morphology carbon spheres from a lignocellulosic biomass in experiments carried out under different conditions in an acidic reaction medium. This is clearly seen from the SEM images. In addition, FTIR spectra and XRD patterns confirm that the sphere was obtained. According to the BET surface area and pore size distribution results, it can be said that the main significant difference is in the mesopore structure of the carbon spheres, even if the surface area values of the samples obtained at different temperatures and different reaction times increase linearly with temperature. In order to determine the usability of carbon spheres obtained in different conditions in the energy field, the gravimetrically measured H₂ storage capacities at cryogenic temperature (77 K) and pressure range of 0–30 bar were determined as maximum 1.1% by weight. When the hydrogen storage capacities of the samples are evaluated together with the BET surface area values and pore size distributions, it shows that the hydrogen storage capacity in carbon spheres is directly proportional to the mesopore volumes. In addition, Langmuir and Freundlich isotherms related to adsorption equilibrium were investigated in order to better define the H₂ adsorption that took place in these samples. Considering the regression coefficients of the obtained isotherms, it was determined that some of the carbon spheres were more compatible with the Langmuir isotherm and some with the Freundlich isotherm.     

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.     

Transparent ceramics prepared from ultrapure magnesium aluminate spinel nanopowders by spark plasma sintering

We have studied the properties of transparent magnesium aluminate spinel ceramics prepared by spark plasma sintering (SPS) of ultrapure nanopowders. The starting powders, of ? 99.98% purity, ranging in specific surface area from 30 to 160 m²/g, were prepared through the hydrolysis of alcoholic solutions of magnesium aluminum alkoxide complexes, followed by calcination at temperatures from 900 to 1100°C. SPS was carried out at 1450°C, with the holding time at the highest temperature not longer than 15 min. The transparent ceramic samples thus prepared have a transmission of up to 73% in the visible and IR spectral regions (λ = 2.5–5.0 µm). The crystallite size in the ceramics is 0.2–0.4 µm, and their microhardness is HV0.1 = 14.8–16.2 GPa.     

Relationship between degassing conditions and tensile properties of Al-20Si-X P/M products

Results are reported which show the effect of different degassing modes on the properties of the Al-20Si-3Cu-1 Mg powder. The paper complements previous papers [1–3] concerning the conventional and modified degassing of the same powder. This research was mainly directed to study the influence of temperature on the tensile properties, ultimate tensile strength, σ_UTS, and elongation, ɛ, of extrudates obtained of Al-20Si-3Cu-1Mg compacts non-degassed, conventionally degassed, and treated by a modified process, namely degassing assisted by flushing with a depurative gas such as argon or nitrogen. The processing of the Al-20Si-3Cu-1Mg P/M powder must include a degassing step which significantly improves the tensile properties, at room and elevated temperatures, of the products of compacted powder with respect to those of the products whose compacts were non-degassed. It is apparent that degassing assisted by flushing with argon or nitrogen gives products with higher tensile properties than those of the products conventionally degassed under optimal conditions of temperature and time and much higher than those of the non-degassed products. The tensile results are in agreement with the theoretical approach to the gas entrapment and evolution of the aluminium powders presented in previous papers.     

Experimental study on thermal properties of frozen soils

A series of measurements of the effective thermal conductivity, specific heat and unfrozen-water content of various soils exposed to a cold environment have been carried out by a transient probe method and a calorimetric technique. The present experiments were performed at a very slow rate of cooling of the moist-soil and using four kinds of soil samples from fine to coarse grain-size. It was established that the amount of unfrozen-water in the frozen soil was dependent on the initial moisture content, the grain-size of the soil and the temperature (below 0°C). Measured values of the effective thermal conductivity and specific heat show a strong dependence on temperature, initial moisture content and grain-size of soil in the temperature range T = 0°C to ?10°C. The anomalous behavior of a decrease in the effective thermal conductivity of frozen soil for the finest grain-size with decreasing temperature (below 0°C) was observed for a large initial moisture content w = 30–40%.     

Study of structural transformations and phases formation upon calcination of Zn–Ni–Al hydrotalcite nanosheets

In this paper, we describe a general process for the synthesis of highly crystalline Zn–Ni–Al hydrotalcite-like materials. The structure and thermal decomposition of the prepared samples are studied by XRD, FT–IR, TG–DSC, SEM, TEM and N₂ adsorption/desorption. The morphology of large-sized, porous and hexagonal platelike Zn–Ni–Al hydrotalcite is affected by calcination temperature. BET specific surface area and pore volume are observed to increase with increase of the calcination temperature up to 700°C followed by a further decrease with increasing temperature.