Polymorphism versus devitrification mechanism: Low-wavenumber Raman investigations in sulindac (original) (raw)
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Using Milling to Explore Physical States: The Amorphous and Polymorphic Forms of Sulindac
Journal of Pharmaceutical Sciences, 2019
This paper shows how milling can be used to explore the phase diagram of pharmaceuticals. This process has been applied to sulindac. A short milling has been found to trigger a polymorphic transformation between form II and form I upon heating which is not seen in the non-milled material. This possibility was clearly demonstrated to result from crystalline micro strains induced by the mechanical shocks. A long milling has been found to induce a total amorphization of the material. Moreover, the amorphous fraction produced during milling appears to have a complex recrystallization upon heating which depends on the milling time. The investigations have been mainly performed by differential scanning calorimetry and powder X-ray diffraction.
Crystallization of micro particles of sulindac using rapid expansion of supercritical solution
Journal of Crystal Growth, 2010
In pharmaceutical industry, many drugs exhibit poor solubility in biological fluid. Solubility of drugs affects on the rate of dissolution and bioavailability in biological fluids. The bioavailability of drugs can be enhanced by decreasing the drug particle size. In this study, sulindac was micronized via rapid expansion of supercritical solution (RESS) where CO2 was used as a solvent. The experiments were conducted to investigate the effect of the extraction pressure and temperature (140-230 bar and 40-60 1C), collection distance (1-10 cm), effective nozzle diameter (450-1700 mm) and nozzle length (2-15 mm) on the size and morphology of the sulindac particles. The size and morphology of the precipitated particles were monitored by scanning electron microscopy (SEM). The particle size of intact sulindac particles was about 33.03 mm, while the average particle size of the micronized sulindac particles was between 0.76 and 8.02 mm based on different experimental conditions. Additionally, the different morphology of the micronized particles was observed like needle, rectangular, quasi spherical and irregular form while the morphology of the intact particles of sulindac was rectangular and irregular.
Materials Chemistry and Physics, 2012
A transparent uniaxial sodium sulfanilate dihydrate (SSDH) single crystal having dimension of 30 mm diameter and 100 mm length was grown by Sankaranarayanan-Ramasamy (SR) method with a growth rate of 1 mm per day. Using an identical solution the conventional crystal grown to a dimension of 12 mm × 20 mm × 5 mm was obtained over a period of 20 days. The crystal structure has been confirmed by single crystal X-ray diffraction (XRD) measurement. The crystalline perfection of sodium sulfanilate dihydrate crystals grown by slow evaporation solution technique (SEST) and SR method were characterized using chemical etching, laser damage threshold, Vickers microhardness, UV-vis NIR, birefringence and dielectric analysis. The above study indicates that the crystal quality of the Sankaranarayanan-Ramasamy (SR) method grown sodium sulfanilate dihydrate is good compared to conventional solution method grown SSDH crystal. The growth features of inclusions, low angle grain boundaries, twins and micro-cracks have been observed in conventional method grown SSDH crystals. The dielectric tensor components for unidirectional method grown sodium sulfanilate dihydrate single crystal were evaluated as a function of temperature at 100 Hz frequency.
1981
Raman spectra are reported for the three known polymorphs of LiAlSiro., for glasses of LiAlSi2O5 composition synthesized at 1500' and l750oC and over the pressure range 0.001-20kbar, and for a glass of Li'rAlSiroucomposition synthesized at I atm and l500oC. A comparison of the spectra of LiAlSirO.-I,-II, and-III indicates that the change in the coordination of Al from four-fold (LiAlSiro6-II and-II! to six-fold (LiAlSiro5-I) results in major changes in the spectra. The observed number of Raman bands are compared with those predicted on the basis offactor group analysis, and we propose that little or no deviation of the structure of a-spodumene from the C2/c space group occurs. The spectra of the glasses of LiAlSirOu composition synthesized over the pressure range 0.001-20 kbar resemble thoge of LiAlSirO6-II and-III, which indicates that Al3* is fourcoordinated in the glasses over the pressure range investigated. The major spectral diferences between the I atm and high-pressure glasses are explained in terms of differences in the symmetry of the local ordering of the network structure and a systematic decrease in the TO -T bond angle with increasing pressure. The overall effect of pressure on the structure of LiAlSirO5 melts is to increase the degree of local ordering and to change the local network structure from phase IIand phase III-like arrangements to a coesite-type structure.
Crystal Growth & Design, 2009
This paper investigated the crystallization of calcium carbonate in saline solution at different temperatures using Raman spectroscopy. Application of an advanced mixture analysis algorithm based on Bayesian theory (BPSS) allowed recovery of the Raman spectra of the three pure anhydrous polymorphs (vaterite, aragonite, and calcite). In particular, the low wavenumber range between 50 and 300 cm-1 , characteristic of crystallographic structure phonons, clearly distinguished the three structures. Contour plots of the polymorph concentrations during the crystallization process vs temperature and time have been established and discussed. This study demonstrated the ability of low wavenumber Raman spectroscopy combined with BPSS analysis to identify the different polymorphs (known or unknown) during a crystallization process and to assay their relative amounts without calibration.
Low-temperature phase transformation studies in the stearic acid: C form
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2015
This paper reports the temperature-dependent measurements in the C form of stearic acid. Raman scattering, X-ray diffraction, and differential scanning calorimetry measurements were performed at low temperatures. The polarized Raman spectra were measured for temperatures ranging from 8 to 300 K over the spectral range of 30-3000 cm À1 . The spectral changes observed in both the lattice vibrational modes and the internal vibrational modes regions of the Raman spectrum, allowed to identify a phase transition undergone by the stearic acid crystal occurring between 210 and 170 K and a change in the structure continues to be observed down to 8 K. The anharmonicity of some vibrational modes and the possible space groups presented by the crystal at low temperatures were also discussed. j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / s a a X-ray powder diffraction Polarized Raman scattering
Two series of mesogenic molecules of variable terminal chain lengths have been synthesised and characterised. The molecules feature a tolane-based rigid core surrounded by two esters groups. The two series differ from each other only by the orientation of an ester linker. Their mesogenic properties have been characterised and are reported. It is found that the orientation of the ester linker and the length of the terminal chain greatly influence their polymorphism. Binary mixtures of the two series have been prepared and their phase diagrams are also reported. They offer some insight at the role of the side chains in the formation of the S C phase.
Influence of K2CO3 on the Growth and Properties of Sulphanilic acid Crystal
Single crystal of Potassium carbonate (PC) added Sulphanilic acid (SA) has been grown from deionized water as solvent by slow evaporation technique with the vision to improve the properties of the crystal. The objective of this study is to show how inorganic material influence the growth and properties of sulphanilic acid crystals. The crystal system was identified, the difference in the lattice constant between pure and PC added SA crystals have been studied and compared by means of single XRD analysis. Intensity variation in the powder X-ray analysis confirms the inclusion of the PC in pure crystal. The FTIR spectral analysis has been carried out to confirm the presence of various functional groups. The UV transmission spectrum was recorded and its cutoff wavelength is around 269 nm. Addition of 1 mol % PC improves the quality and transmission efficiency. The optical band gap energy of the crystal has also been evaluated. In addition, the sharp PL emission peak at 546 nm in PLE spectrum revealed that, the grown crystal exhibits green shift emission. To study the thermal and mechanical properties, TGA/DTA and Vickers micro hardness test were carried out. The SHG efficiency of the crystal was confirmed using Kurtz and Perry technique
International journal of pharmaceutics, 2011
We show in this paper the contribution of the whole Raman spectrum including the phonon spectrum, to detect, identify and characterize polymorphic forms of molecular compounds, and study their stability and transformation. Obtaining these kinds of information is important in the area of pharmaceutical compounds. Two different polymorphic systems are analyzed through investigations in indomethacin and caffeine exposed to variable environmental conditions and various stresses, as possibly throughout the production cycle of the active pharmaceutical ingredient. It is shown the capability of the low-frequency Raman spectroscopy to reveal disorder in the crystalline state, to detect small amorphous or crystalline material, and to elucidate ambiguous polymorphic or polyamorphic situations.
Vibrational Spectroscopy, 2012
Methyldopa sesquihydrate (C 10 H 13 NO 4 ·1.5H 2 O) is a substance used in the treatment of hypertension being one of the most widely used drugs in the world. In this work we have studied the stability of this drug as a function of temperature using four different techniques: X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry and Raman spectroscopy. From the combination of these techniques we were able to infer about a set of phase transitions during the loss of water from the crystal around the temperatures of 388 K (changes only in the lattice modes) and between temperatures 393 and 423 K, when all water leaves the crystal and changes in some lattice modes and in some internal modes occur.