MICROMERITICS relative

Evaluation of the morphology of a pharmaceutical solid is of extreme importance, since this property exerts a significant influence over the bulk powder properties of the material. In addition to providing insights into the micromeritic properties of the solid, microscopy can also be used to develop preliminary estimations of the particle-size distribution. A determination can be easily made regarding the relative crystallinity of the material, and it is often possible to deduce crystallographic information as well. Unknown particulates can often be identified solely on the basis of their microscopic characteristics, although it is useful to obtain confirmatory support for these conclusions with the aid of microscopically assisted techniques. 

Nitrogen adsorption - desorption isotherms were obtained from a volumetric adsorption analyzer ASAP 2010 manufactured by Micromeritics. The samples were first degassed for several hours at 350°C. The measurements were then carried out at -196°C over a wide relative pressure range from 0.01 to 0.995. The average pore diameter and the pore size distribution were determined by the B JH method from the adsorption branch of isotherm [18],... 

Nitrogen adsorption measurements were done using a Micromeritics model ASAP 2010 adsorption analyzer (Norcross, GA). Adsorption isotherms were measured at -196°C over the interval of relative pressures from 10 6 to 0.995 using nitrogen of 99.998% purity. Before each analysis the sample was degassed for 2 hours at 150°C under vacuum of about 10 Torr in the degas port of the adsorption apparatus. 

A low temperature nitrogen sorption was carried out on an automated physisorption instrument (ASAP 2000, Micromeritics Instrument Corporation). Before the measurement, the sample was degassed at 350 C for 4-5 h until the vacuum of system was better than 0.67 Pa. The data for micropore were obtained from t-plot, and those for mesopore and distribution of mesopore were calculated by BJH method (using desorption curve). The single point total pore volume at high relative pressure was taken as the total volume. 

Nitrogen adsorption isotherms for the OMMs studied were recorded at 77K using a Micromeritics ASAP 2010 adsorption analyzer. All samples prior to adsorption analysis were degassed at 120°C for 2h under vacuum. The BET specific surface area was calculated from the adsorption data in the range of the relative pressure from 0.04 to 0.2 according to the BET method.46 The total pore volume was estimated from the amount adsorbed taken at the relative pressure about 0.99.47 The pore width was estimated at the pore size distribution maximum obtained by the KJS method.48... 

Textural characterization was performed by N2 adsorption-desorption at 77 K using a Micromeritics ASAP 2010 analyzer. The samples were preheated under vacuum in three steps of Ih at 423 K, Ih at 513 K, and finally 4 h at 623 K. BET specific surface area, Sbet, was calculated using adsorption data in the relative pressure range, P/Po, from 0.05 to 0.2. Total pore volume, Vp , was estimated by Gurvitsch rule on the basis of the amount adsorbed at P/Po of about 0.95. The primary mesopore diameter, Dp, was evaluated using the BJH method from the desorption data of the isotherm. The primary mesopore volume, Vp, and the external surface area, Sext were determined using the t-plot method with the statistical film thickness curve of a macroporous silica gel [5]. 

Adsorption/desorption isotherms of nitrogen at 77 K were measured with an automated apparatus ASAP 2010 (Micromeritics, USA). The specific surface areas, Sbet, were calculated from the linear form of the BET equation, taking the cross-sectional area of the nitrogen molecule to be 16.210 m. Pore size distributions were calculated in the standard maimer by using BJH method [6]. The total pore volumes, Vp, for the samples under study were determined from a single point adsorption at a relative pressure of 0.98 by converting the value of the adsorbed gas to the volume of the liquid adsorbate. 

X-ray powder diffraction (XRD) patterns were taken on a Spectrolab CPS Series 3000 120 diffractometer, using Ni filtered Cu Ka radiation. The nitrogen adsorption isotherms were determined at 77 K by means of a Micromeritics Gemini 2370 surface area analyser. Surface areas were derived from the BET equation in the relative pressure range 0.05-0.25, assuming a cross-sectional area of 0.162 nm" for the nitrogen molecule [ 18]. 

Textural properties of fresh and deactivated samples were determined using an ASAP 2000 analyzer (Micromeritics). To determine total surface area, the BET equation was applied to adsorption uptakes obtained in the relative pressure interval, P/Po, of 0.01 to 0.05. Zeolite and matrix surface areas were determined according to the ASTM D-4365 method, using P/Po pressures of 0.01 to 0.60. Mesopore volume and pore-size distribution were determined according to the ASTM D-4222 method at P/Po relative pressures of 0.01 to 0.99. 

X-ray diffraction patterns were recorded on a Siemens D5000 diffractometer using CuKa radiation. Thermogravimetric and differential thermal analysis curves were recorded on a Setaram Setsys 12 thermal analysis station by heating in an argon atmosphere from 25 to 1200 -C at a rate of 5 min". Samples were used untreated. The Pt content was determined by the Service Central d Analyse, CNRS (Vernaison, France) and the microanalyses (C, H) were performed at Complutense University (Madrid, Spain). Na isotherms were determined on a Micromeritics ASAP 2000 analyzer. H MAS NMR, Si MAS NMR and C CP MAS NMR spectra were recorded at 400.13, 79.49 and 100.61 MHz, respectively, on a Broker ACP-400 spectrometer at room temperature. An overall 1000 free induction decays were accumulated. The excitation pulse and recycle time for H MAS NMR spectra were 5 ps and 3 s, respectively, those for Si MAS NMR spectra 6 ps and 60 s and those for C CP MAS NMR spectra 6 ps and 2 s. Chemical shifts were measured relative to a tetramethylsilane standard. Prior to measurement, if necessary, samples were dehydrated in a stove at 423 K for 24 h. 

The characterization of the physical properties of pharmaceutical compounds under development is often conducted using a variety of techniques including DSC, TGA, XRD, HSM, solid-state nuclear magnetic resonance (NMR), infrared (IR) and Raman spectroscopy, moisture uptake, particle size analysis, scanning electron microscopy (SEM), and micromeritic assays. A typical initial analysis of a pharmaceutical compound under development in a materials characterization group would include DSC, TGA, HSM, and XRD analyses. These four techniques are chosen because the data generated from them, when viewed collectively, comprise a relatively complete initial analysis of the physical properties of the compound. The DSC, TGA, and HSM assays... 

In order to evaluate the formation of secondary pores within the zeolite structure in the course of the sulfidation and the growth of sulfide particles adsorption and desorption isotherms of cyclopentane vapours were measured at 293 K (Micromeritics Accusorb 2100 E). Prior to the adsorption studies each sample was evacuated for 30 h at a temperature of 623 K until a pressure of 10- Pa was attained. Adsorption-desorption cycles were followed up to relative pressures... 

Az physisorption measurements. The catalyst and support surface areas were measured by physisorption of Nz at -196°C on a Micromeritics ASAP 2000 instrument. Prior to measurement, samples were outgassed overnight at 150°C under 0.13 Pa. Surface area values were computed using the BET equation from the amount of Nz physisorbed at different relative pressures. 

ICP analyses were performed by Plasma Absorption Emission Spectroscopy (ICP-AES). BET surface areas were measured with a Micromeritics TriStar 3000 instrument after degassing the samples at 150 C under a 0.13 Pa vacuum overnight. XPS analyses were performed on a SSI X-probe spectrometer (SSX-100/206 photoelectron spectrometer Fisons) equipped with a monochromatized microfocused Al Ka X-ray source (1486.6 eV) and a hemispherical analyser. The binding energies were calculated relative to the C-(C, H) component of the adventitious Cls carbon peak fixed at 284.8 eV. Zeta potential measurements were carried out in a PENKEM Zeta Meter 500, using 25 mg of sample ultrasonically dispersed in 200 ml of an aqueous solution... 

Sur ce area and pore size characterizations were performed using a Micromeritics ASAP2000 gas adsorption surface area analyzer. The specific surface area of the samples was determined from the nitrogen isotherms at 77K and by using the BET equation. Micropore volume was determined using the DR equation and the total volume of pores was calculate at a relative pressure (p/p ) of 0.97. Table 1 shows the activation conditions and the structural characterization. More details are given elsewhere [3]. 

The nitrogen adsorption/desorption isotherms were measured at 77 K using the ASAP 2010 volumetric adsorption analyzer (Micromeritics Inc., Norcross, GA). The specific surface areas of the investigated samples were determined using the standard BET method at the relative pressure p/po in the range 0.04 to 0.25. The total pore volume was estimated fium single point adsorption at the relative pressure of about 0.99. 

Nitrogen sorption isotherms were leonded at 77 K, using a Micromeritics ASAP 2000. Prior to analysis, the samples were de sed overnight at 150°C under vacuum. BET surfoce areas were cdculated using adsorption data recorded in the relative inessure range, 0.05 - 0.2. The total pore volume was derived fixnn the amount of gas adsorbed at a relative pressure of 0.99. Pore sizes were determined by the BdB-FHH method [14]. This method allows flie determination of spherical cell size fixnn the adsorption branch and window size fixrm die desorption branch of the isotherm. 

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