J.R. Matos

Thermal behavior and stability of biodegradable spray-dried microparticles containing triamcinolone.

Thermal analysis has been widely used for obtaining information about drug-polymer interactions and for pre-formulation studies of pharmaceutical dosage forms. In this work, biodegradable microparticles of poly (d,L-lactide-co-glycolide) (PLGA) containing triamcinolone (TR) in various drug:polymer ratios were produced by spray drying. The main purpose of this study was to study the effect of the spray-drying process not only on the drug-polymer interactions but also on the stability of microparticles using differential scanning calorimetry (DSC), thermogravimetry (TG) and derivative thermogravimetry (DTG), X-ray analysis (XRD), and infrared spectroscopy (IR). The evaluation of drug-polymer interactions and the pre-formulation studies were assessed using the DSC, TG and DTG, and IR. The quantitative analysis of drugs entrapped in PLGA microparticles was performed by the HPLC method. The results showed high levels of drug-loading efficiency for all used drug:polymer ratio, and the polymorph used for preparing the microparticles was the form B. The DSC and TG/DTG profiles for drug-loaded microparticles were very similar to those for the physical mixtures of the components. Therefore, a correlation between drug content and the structural and thermal properties of drug-loaded PLGA microparticles was established. These data indicate that the spray-drying technique does not affect the physico-chemical stability of the microparticle components. These results are in agreement with the IR analysis demonstrating that no significant chemical interaction occurs between TR and PLGA in both physical mixtures and microparticles. The results of the X-ray analysis are in agreement with the thermal analysis data showing that the amorphous form of TR prevails over a small fraction of crystalline phase of the drug also present in the TR-loaded microparticles. From the pre-formulation studies, we have found that the spray-drying methodology is an efficient process for obtaining TR-loaded PLGA microparticles.

Preparation and thermal decomposition of solid state compounds of 4-methoxybenzylidenepyruvate with alkali earth metals, except beryllium and radium

Abstract Solid compounds of general formula ML 2 · n H 2 O [where M is Mg, Ca, Sr or Ba; L = 4 methoxybenzylidenepyruvate (4-MeO-BP); n = 4, 1 or 0] have been synthetized. Thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), x-ray diffraction powder patterns and elemental analysis have been used to characterize the compounds. The thermal stability of these compounds as well as that of the decomposition products were studied using Pt or Al 2 O 3 crucibles in an air or a CO 2 atmosphere.

Thermogravimetric study of lanthanoid picrate complexes with dimethylsulfoxide (DMSO)

Abstract Complexes of composition Ln(pic)3·3DMSO (Ln is Ce, Nd, Sm-Tb, Ho-Lu, Y; pic is picrate) were investigated by thermogravimetry in order to detect their decomposition products.

Synthesis, identification and thermal decomposition of double sulfites like Cu2SO3·MSO3·2H2O (M=Cu, Fe, Mn or Cd)

Double sulfites with empirical formula Cu2SO3·MSO3·2H2O (where M is Cu, Fe, Mn, or Cd) were obtained by saturation with sulfur dioxide gas of an aqueous mixture of MII sulfate and copper sulfate at room temperature. The salts obtained were identified by infrared spectra, X-ray powder diffraction and elemental analysis. The compounds studied are isostructural with the CuII replacement by MnII, FeII, and CdII in Chevreul’s salt (Cu2SO3·CuSO3·2H2O). The thermal behavior of the double sulfites was evaluated by thermogravimetry analysis (nitrogen and air atmospheres) and differential scanning calorimetry. These salts are thermally stable up to 200°C. The structures of sulfite ion coordination influence strongly the course of the thermal decomposition. The sulfite species coordinated to the metal through the oxygen are easier oxidized to sulfate than sulfur-coordinated species, leading to preferential formation of MIISO4 and Cu2O in the first step. The weight gain relative to the second step can be due to oxidation of Cu2O to CuO and/or oxidation of MIISO3 to MIISO4 probably by self-generated atmosphere formed by dense volatile products liberated in the latter step.

Thermal behaviour of the basic carbonates of lanthanum-europium

Abstract The basic carbonates of lanthanum with 10%, 20%, 50% and 80% of europium were prepared by precipitation from homogeneous solutions via the hydrolysis of urea, without the addition of an auxiliary anion, at two different temperatures. Elemental analysis, complexometric methods, X-ray diffraction patterns, solid state IR absorption, thermogravimetry/derivative thermogravimetry (TG/DTG) and differential thermal analysis (DTA) were used to characterise the compounds and study their thermal behaviour.

Crystal structures, spectroscopic, TG and DSC studies of lanthanide picrate complexes with 4-methylmorpholine N-oxide (MMNO)

Abstract The crystal structures, IR absorption spectra, emission spectrum of the europium compound, TG and DSC analyses of Ln(pic) 3 ·MMNO·2H 2 O (pic=picrate, Ln=La, Nd, Eu) complexes are reported. The crystals that were grown from methanolic solutions, are isomorphous belonging to the triclinic space group P 1. The Ln ions are coordinated to nine oxygen atoms, six of the picrate moieties, one of the MMNO and two of water molecules, giving rise to a tricapped trigonal prism.

Lanthanon picrate complexes with tetramethylenesulfoxide (TMSO)

Abstract Compounds with composition Ln(pic) 3 · 3TMSO (pic is picrate, Ln is La, Nd, Eu, Gd, Er, Yb and Y) were synthesized and characterized. A thermogravimetric study was performed in order to determine their decomposition products.

Thermal decomposition of some dimethylsulphoxide (DMSO) lanthanide complexes

Abstract Compounds of composition LnCl 3 ·3MDSO (Ln = Dy-Lu) were prepared and characterized. The thermal decomposition was investigated by TG and DSC techniques.

Thermal Decomposition of Hydrated Lanthanide Picrates by TG/DTG and DSC Analyses

Hydrated lanthanide picrates with a composition of: Ln(pic)3⋅xH2O (Ln=La–Lu, Y) were synthesized and characterized. Thermal decomposition of the picrates by TG/DTG and DSC techniques are reported.

Synthesis, characterization, properties and thermal study of lanthanoid isothiocyanate complexes with 2,6-lutidine-N-oxide (2,6-LNO)

Abstract Lanthanoid isothiocyanate complexes of general formula Ln(NCS) 3 (2,6-LNO) 3 (H 2 O) n , where n is 3, for Ln is La, n is 1, for Ln is Ce-Nd and Eu-Tb, and n is 0 for Ln is Tm, Lu, Y, were synthesized and characterized. They behave as non-electrolytes in acetonitrile. The anion is bonded through the nitrogen and 2,6-LNO through the oxygen. The nephelauxetic parameter, covalent factor and Sinhas parameter and also the oscillator strength in acetonitrile solution were calculated from the neodymium absorption spectra. A C 3v symmetry and a monocaped trigonal prismatic geometry, with the water molecule located on the rotation axis, was deduced from the emission spectrum of the europium compound. The similarities between the emission spectra of the europium complex and the europium-doped lanthanum and lutetium adducts suggests that the central ions are also involved in a C 3v symmetry. The TG, DTG and DSC measurement were recorded in dynamic air and nitrogen atmospheres and interpreted.