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PubMed1989

Crystallographic properties of a series of synthetic hydroxyapatites.

The crystallographic properties of hydroxyapatites synthesized at temperatures of 200 degrees C, 500 degrees C, 900 degrees C and 1250 degrees C, designated HAP200, HAP500, HAP900 and HAP1250, respectively, were studied using X-ray powder diffraction. Values of a-axis length for the hydroxyapatites ranged from 9.406 A to 9.416 A, which were smaller than the corresponding value for stoichimetric hydroxyapatite, a = 9.418 A. Generally, the a-axis length decreased with the synthesis temperature, except for HAP500 which showed the smallest value. Crystallinity of the hydroxyapatites, measured by X-ray diffraction peak broadening as full width at the half-maximum value (FWHM), increased with the synthesis temperature, although HAP500 showed a decrease. These results suggest that the synthetic hydroxyapatites contained some carbonate ions, probably at the A-site of the apatite structure, and that the structure was depleted of carbonate ions at about 500 degrees C.

Crystallography↗
PubMed1990

X-ray crystallography of incisor enamel from red kangaroo.

X-ray powder diffraction of red kangaroo (Macropus rufus) dental enamel, with a relative density greater than 2.60, showed a longer a-axis length of the apatite unit cell, a = 9.462 A, a shorter c-axis length, c = 6.877 A, and a smaller crystallite size, ca. 185 A, than those of human dental enamel. The a-axis of red kangaroo dental enamel was one of the longest among the values reported previously, whereas the c-axis was one of the shortest. The crystallite size was almost equal to that of dentin crystallites. It is suggested that the chemical composition of the dental enamel apatite of the red kangaroo is markedly substituted, resulting in lattice distortion.

Animals↗
PubMed1998

Solubilization and interaction of sulindac with polyvinylpyrrolidone K30 in the solid state and in aqueous solution.

In this report the interactions of sulindac with polyvinylpyrrolidone K30 (PVP K30), both in the solid state and in aqueous solution, have been investigated. Solid dispersions of sulindac with PVP K30 were prepared by the solvent method in ethanol from various drug-to-polymer weight ratios. X-ray powder diffraction and differential scanning calorimetry have shown that PVP inhibits the crystallization of sulindac. The stabilization of the noncrystalline state of sulindac was shown by x-ray diffractometry after a 1-year storage. There was a considerable increase in the release rate of the drug when the polymer content was increased and the intrinsic dissolution rate values of these systems were calculated. From the UV spectra a bathochromic shift and a well-defined isosbestic point were observed at pH 2 and 6, which confirmed an interaction between the drug and the polymer in solution. Moreover, the apparent solubility of sulindac has been modified as a function of the polymer concentrations. The binding process between the drug and PVP was exothermic from the stability constant values at 25, 30, and 37 degrees C at pH 2.

Calorimetry, Differential Scanning↗
PubMed1998

Solubilization and interaction of sulindac with beta-cyclodextrin in the solid state and in aqueous solution.

A sulindac-beta-cyclodextrin complex was obtained by the coprecipitation method. Kneaded solids and physical mixtures were also prepared. The complex was shown by x-ray powder diffraction to be noncrystalline whereas pure drug and any of the other sulindac-beta-CD system were crystalline. the endothermic peak of sulindac due to the fusion of drug disappeared in DSC thermograms for the coprecipitate product, which confirmed the interaction between sulindac and beta-CD in the solid state. After a 1-year storage drug crystals could not be observed by x-ray diffractometry, which indicated that the complex formed was stable. The complex showed the fastest dissolution rate which might be attributed to the high-energy noncrystalline state and the inclusion complex formation in solution. UV spectra were modified and the apparent solubility of the drug increased with the addition of beta-CD, which confirmed the interaction between sulindac and the ligand in solution. The apparent stability constant, K1:1, for the complex at pH 2 and 25, 30, and 37 degrees C was 340, 220, and 160 M-1, respectively, which confirmed the influence of temperature on the complex stability. The value of K1:1 at pH 6 and 25 degrees C was 139 M-1, which indicated that the complex is formed easier with the non-ionized sulindac. The enthalpy change, delta H degree, showed that the binding process is exothermic.

Chemical Phenomena↗
PubMed1996

The impact of crystallinity on Brequinar sodium hygroscopicity.

The hygroscopicity of Brequinar sodium, an organ transplant immunosuppressant, at 75% relative humidity highly depends on the crystal form or crystallinity of the drug substance. Hygroscopicity and ease of water uptake of three lots of Brequinar sodium were investigated. Those lots contained different impurities at levels ranging from 0.26% to 0.5%. DSC thermograms of the hydrated samples suggest that unbound/loosely bound water was released around 90 degrees C and water of hydration was released at 175 degrees C. At equilibrium, 2% of the water was tightly bound. Stoichiometry suggests that this is a hemihydrate. Unbound/loosely bound water has no impact on the hemihydrate crystal structure as indicated by x-ray powder diffraction patterns. The results suggest that the less perfect crystals exhibited a faster water uptake and converted to a stable hemihydrate when stored at 75% relative humidity. Both the anhydrous and the hemihydrate forms of Brequinar sodium exhibited rapid dissolution rate and comparable water solubility.

Biphenyl Compounds↗
PubMed1998

Formulations of sugars with amino acids or mannitol--influence of concentration ratio on the properties of the freeze-concentrate and the lyophilizate.

Formulations consisting of either sucrose or trehalose with glycine, lysine-HCl, or mannitol were studied to determine how the ratio of the excipients affects the design of the lyophilization program and the properties of the final cake. Glass transitions (Tg', Tg), crystallization temperatures, and eutectic melting temperatures were measured by differential scanning calorimetry, the physical state of the excipients was determined by x-ray powder diffraction, and residual moisture was measured by Karl Fischer titration. The addition of increasing amounts of glycine, lysine-HCl, or mannitol to a sucrose solution caused a progressive depression of the Tg', an effect that was more pronounced with the amino acids. In equivalent ratios with sucrose, the two amino acids induced a comparable Tg' shift due to their low Tg' values. For lysine-HCl, two apparent Tg' with midpoint temperatures of -69 and -56 degrees C were measured. For mannitol, the Tg' depression was unexpected because mannitol exhibits a higher Tg' than that of sucrose. During lyophilization, the ratio of the amorphous amino acids or mannitol to the sugar determined whether crystallization could be induced by an annealing step performed after freezing. Crystallization could be verified by a shift of the formerly depressed Tg' back to the value of the sugar and by the detection of the eutectic melting peak of the crystallized compound. The crystallized excipients served as excellent bulking agents. In the freeze-dried cake, amorphous glycine and even more amorphous mannitol lowered the Tg value. If the cake was stored above Tg, subsequent crystallization of mannitol occurred. The results emphasize that the qualitative and quantitative composition of a formulation has profound implications on the design of a lyophilization program and on the characteristics of the freeze-dried cake.

Amino Acids↗
PubMed1998

In situ salt screening--a useful technique for discovery support and preformulation studies.

The purpose of this paper was to present an in situ salt screening technique which is applicable to most basic compounds. The theoretical aspects, experimental details, applications, and significance of this technique are illustrated through in situ salt screening studies performed on GW1818, an alpha 1A andrenergic receptor antagonist intended for treatment of benign prostatic hyperplasia (BPH). Generally, the in situ salt screening technique includes (i) acid selection, (ii) a solubility study, (iii) characterization of residual solids, and (iv) calculation of the Ksp and solubility of the salts. Six acids were screened for salt formation with GW1818. Excellent agreement was found between the solubility results determined using the authentic salts and solubility results obtained through in situ screening. Additional evidence of salt formation and some solid state properties of the salts formed in situ were obtained through microscopic examinations, differential scanning calorimetry (DSC), and x-ray powder diffraction studies. Four salts of GW1818, the phosphate, succinate, mesylate, and hydrochloride, were crystalline and demonstrated adequate solubility. These were selected for further evaluation. Adequate solubility was also observed in the case of citrate and tartrate salts, but these were considered only as potential backup candidates because they were difficult to crystallize. The results of the in situ salt screening experiments also led to the development of an IV formulation for use in pilot toxicological studies and pharmacological studies. In conclusion, the in situ salt screening technique offers a time- and compound-conserving approach for prioritizing salt selection and for providing solubility and stability information useful for formulation development both in the research and the development stages.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1999

Destructive tophaceous calcium hydroxyapatite tumor of the infratemporal fossa. Case report and review of the literature.

Tophaceous pseudogout is one of the rarest forms of crystal deposition disease, typically presenting as a destructive and invasive mass involving the temporomandibular joint or the infratemporal fossa region in the absence of any other articular manifestations. Previous cases have been assumed to be caused by calcium pyrophosphate dihydrate (CPPD) crystal deposition, based on finding weakly birefringent crystals in the involved tissues. The authors present the unique case of a 65-year-old woman with a destructive and invasive facial mass extending to the middle cranial fossa with microscopic and clinical features consistent with tophaceous pseudogout. High-resolution x-ray crystallographic powder diffraction and Fourier transformed infrared spectroscopy subsequently revealed that the crystals were composed of calcium hydroxyapatite without CPPD. The patient was later found to have primary hyperparathyroidism and mild hypercalcemia. This case demonstrates that tissue deposits of calcium hydroxyapatite can cause a destructive and invasive mass containing weakly birefringent crystals and raises the question of whether previous cases attributed to tophaceous pseudogout resulting from CPPD actually were composed of birefringent calcium hydroxyapatite.

Aged↗
PubMed1999

Calcium phosphates produced by physical methods in the treatment of dentin hypersensitivity.

BACKGROUND: The aim of this paper is to study the properties of innovative materials based on defective calcium phosphates produced by physical methods in the therapy of dentin hypersensitivity. METHODS: In particular, the effects of gels, aqueous solutions and toothpastes containing the above mentioned materials on dentinal permeability measured as dentin hydraulic conductance have been studied. The calcium phosphates have been characterized by X-ray powder diffraction (Rietveld analysis) and Fourier transform infra-red analysis. In addition, scanning electron microscopy has been performed to study the surface of dentin and enamel after treatment with the phosphates. In particular sound occlusal dentin, sound cervical dentin, carious occlusal dentin, sound buccal enamel and carious buccal enamel have been observed. RESULTS: The results have shown that these biocompatible materials can be produced with chemical and physical characteristics very similar to dentin and/or enamel. By forming a protective layer inside and outside the dentin tubuli, the calcium phosphates significantly reduce the dentinal hypersensitivity. CONCLUSIONS: These phosphates seem to be a promising material for clinical application.

Calcium Phosphates↗
PubMedDate not supplied

Accurate quantitative measurements of asbestos in XRPD analysis.

X-ray Powder Diffraction (XRPD) quantitative analysis of fibrous substances like asbestos, is strongly influenced by systematic errors due to preferred orientation, as a consequence of their morphology. In the present work we have compared the accuracy of quantitative measurements performed by using the Internal Standard (IS) method and the Reference Intensity Ratio (RIR) method in the analysis of the same diffractographs. Both these analytical methods are based on the same principle but the data analysis procedures are different. We have particularly studied how, in the RIR case, the evaluation of several diffraction lines of both phases, standard and unknown, increases the accuracy of a quantitative determination, balancing the different effect due to systematic errors on the measurements of distinct peaks.

Asbestos↗
PubMed2002

[Crystalline polymorphism of eflucimibe].

The importance, in therapeutics, of the concept of bioavailability and on-going quality research in the formulation of a drug has prompted us to examine the crystalline polymorphism of eflucimibe as from the research phase. This study has been carried out by re-crystallization of the product in organic solvents having a different polarity in a variety of experimental temperature and pressure conditions, then, subsequently, by re-cooling the previously dissolved substance. The analytical methods applied to identify and then describe the polymorphic forms are thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), X-ray powder diffraction from synchrotron radiation (XRPD), infrared spectrometry (IR), solid-state nuclear magnetic resonance spectrometry (SSNMR) and lastly maximum solubility measurements. By means of XRPD, two polymorphic forms called A and B have been clearly identified at ambient temperature. These two crystalline forms were obtained in a reproducible way, then described by DSC, XRPD, IR and SSNMR. Differential scanning calorimetry analysis has shown for polymorphic form A two endothermic phenomena with low energy at about 35 masculine and 118 degrees C attributed by XRDP to conformational polymorphism. The complex endothermic event that extends between 75 masculine and 105 degrees C appears to correspond to successive alterations of a lamellar structure. The solid-solid transition observed at 110 degrees C is due to a change of crystalline phase, then the melting point occurring at about 130 degrees C. For form B, two changes of crystalline phase are clearly observed at about 80 masculine and 120 degrees C. The reversibility of these changes was observed by thermomicroscopy in polarized light. Form A, which is less soluble in absolute ethanol than form B, is the more stable thermodynamically in the temperature range from 25 masculine to 50 degrees C where the data have been obtained. The Van't Hoff diagram layout for each polymorphic form appears to reveal an A<-->B transition temperature in a temperature range lower than 25 degrees C. This study, undertaken as from the research phase, has enabled us to highlight the polymorphism of this new chemical entity by means of XRDP by explaining the nature of the endothermic phenomena observed by DSC, and lastly identify the thermodynamically more stable polymorphic form, thus contributing to a better knowledge of this future drug.

Anilides↗
PubMed2002

Decolorization of reactive bright red K2G dye: electrochemical process catalyzed by manganese mineral.

This paper presents the results of the decolorization of azo dye K2G by the electrochemical process catalyzed by manganese mineral. It is proved that the MnOOH(s), main component of the manganese mineral, can catalyze the electrochemical process and enhance the decolorization efficiency. X-ray powder diffraction spectrum shows that the content of MnOOH(s) has not been changed at the end of the reaction. The effects of initial pH value, current density, concentration of electrolyte on the decolorization efficiency of the dye were investigated in detail. The initial pH effect on the decolorization efficiency of K2G dye is found not to be significant. The optimum current density is 0.26 A/dm2. In addition, a proposed catalyzing mechanism of manganese mineral is discussed in this paper.

Azo Compounds↗
PubMed2002

[Discussion of the application of three-point interaction principle to the phenylglycine racemic compound in IR spectrometry and its enantiomers separation in HPLC].

AIM: To discuss the relationship between the three-point interaction principle in the stereoselective separation of chromatography and applying this principle to survey the infrared spectrometry of racemate. METHODS: In proving the applicability of the three-point interaction principal in IR spectrometry, a special case was found that phenylglycine did not obtain enantioselective separation on the chiral column but its IR spectrometry still obey this principle and explained such special case by experiment. RESULTS: After an equal quantity of solid crystal of d-phenylglycine and l-phenylglycine were mixed and ground for several minutes, they transformed to racemic compound. X-powder diffraction also confirmed this fact. CONCLUSION: The three-point principle was relatively reliable when it was used in the enantioselective chromatography separation and the IR spectrometric analysis. The reason of the fact that phenylglycine was not separated by chiral column can be explained by the fact that the acting force between the three polarity groups in the enantiomers is so strong that they can not form the instantaneous diastereoisomer with the chiral column, it was agreeable with the phenomenon that racemic mixture easily became racemic compound only by simply grinding the mixture in IR spectrometric experiment.

Chromatography, High Pressure Liquid↗
PubMed2002

[Relativities between lattice changes and the function of dissolution improvement of poorly soluble drug silymarin based upon PEG 6,000 solid dispersion system].

AIM: To investigate the lattice mechanisms involved in the increased dissolution effect of polyethylene glycol (PEG 6,000) dispersion system on poorly soluble drug silymarin (SILY). METHODS: Fusion method was used to prepare the solid dispersions of SILY with PEG 6,000. Evaluation of the improvement of dissolution was performed with dissolution studies in vitro. X-ray powder diffraction combined with diffraction peak pattern-fitting procedure were applied to quantitatively analyze the changes of lattice parameters. The interaction of SILY and PEG 6,000 was also determined with Fourier transform-infrared (FT-IR) spectroscopy. RESULTS: The dissolution rate of SILY was considerably increased when formulated in solid dispersion of PEG 6,000 as compared to pure SILY. The datum from the X-ray diffraction showed the changes in the lattic spacings and particular diffraction peaks (position and the intensity) of PEG 6,000 and SILY. These could explain the increased rate of SILY released from solid dispersion system. The information of FT-IR spectroscopy showed the absence of well-defined drug-polymer interaction. CONCLUSION: The dissolution improvement of poorly soluble SILY from solid dispersion of PEG 6,000 can be illuminated by the changes of the lattice parameters of PEG 6,000 and the drug.

Chemistry, Pharmaceutical↗
PubMed2002

[Solid phase coordination synthesis and characterization of polymimide and Sm ion-under microwave radiation].

Solid phase coordination reaction of Sm3+ and the resultant of the imidization of polycondensor of polycondensation and imidization of benzoguanamine(BGA) and 2, 4-tolylenediisocyanate (TDI) and pyromellitic dianhydride (PMIDA) under microwave irradiation were synthesized and studied. The effect of microwave irradiation time (power), the composition of reactants and the reaction temperature on the yield and Sm content in complexes were studied. The complex was determined by Fourier transform infrared absorption (FTIR), Fourier transform Roman spectrum (FTRS), scanning electric minor (SEM), 13C solid state nuclear magnetic resonance spectrometry and X-ray powder diffraction. The fluorescence intensity was measured by fluorescent emission spectrum and compared with thermal coordination. The magnetic susceptibilities were measured by magnetic curve. The results showed that the complex had not characteristic fluorescence of Sm3+, which illustrated that the first excitation level of Sm3+ and polymer could not match at all. But the complex showed good magnetic property of the ion.

Magnetic Resonance Spectroscopy↗
PubMed2003

[Raw material synthesis and characterization of YVO4 birefringent crystal].

In this paper, synthesis of YOV4 birefringence crystal raw material in liquid phase was studied. Mostly, the effects of solution's pH values and some other synthesis conditions on purity and whiteness were discussed. Infra-red spectrometry, X-ray powder diffraction and UV spectrometry were used in the characterization of the raw material and single crystal, and in this way the best method of synthesis was defined. The result of the study indicates that the purity of the raw material had decisive effect on the crystal growth. Flawless crystal with the dimensions of phi 40 x 40 x 50 mm3 was grown by Czochralski (CZ) technique.

Birefringence↗
PubMed2001

[FTIR study of transition metal 2-acrylamido-2-methyl-1-propanesulfonates].

Compounds of transition metal ion (Cu2+, Co2+, Ni2+) 2-acrylamidomethyl-2-methyl-1-propanesulfonates were studied by FTIR and X-ray powder diffraction techniques. The FTIR spectra of Co and Ni compound are similar but are different from that of Cu compound. The results of X-ray diffraction indicated that the crystal structure of Co and Ni compound are different.

Acrylamides↗