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1.
Bogdan Tita Ionut Ledeti Geza Bandur Dumitru Tita 《Journal of Thermal Analysis and Calorimetry》2014,118(2):1293-1304
Thermal analysis is a routine method for analysis of drugs and substances of pharmaceutical interest. Thermogravimetry/derivative thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC) are thermoanalytical methods which offer important information about the physical and chemical properties of drugs (purity, stability, phase transition, polymorphism, compatibility, kinetic analysis, etc.). This work exemplifies a general method of studying the drug-excipient interactions with the aim of predicting rapidly and inexpensively the long thermal stability of their mixtures. The TG/DTG and DSC were used as screening techniques for assessing the compatibility between indomethacin (IND) and its physical associations as binary mixtures with some common excipients. Based on their frequent use in preformulations eleven different excipients: corn starch, microcrystalline cellulose (PH 101; PH 102), colloidal silicon dioxide, lactose (monohydrate and anhydre), polyvinilpyrrolidone K30, magnesium stearate, talc, stearic acid, and manitol were blended with IND. The samples were prepared by mixing the analyte and excipients in a proportion of 1:1 (w:w). In order to investigate the possible interactions between the components, the thermal curves of IND and each selected excipient were compared with those of their 1:1 (w/w) physical mixtures. FT-IR spectroscopy and X-ray powder diffraction were used as complementary techniques to adequately implement and assist in interpretation of thermal results. On the basis of thermal results, confirmed by FT-IR and X-ray analyses, a possible interaction was found between IND with polyvinylpyrrolidone K30, magnesium stearate, and stearic acid. 相似文献
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3.
Liliana-Marinela Ştefan Ana-Maria Pană Geza Bandur Patrick Martin Marcel Popa Lucian-Mircea Rusnac 《Journal of Thermal Analysis and Calorimetry》2013,111(1):789-797
A novel monomer carrying carbohydrate moiety was prepared by simple reaction of methacrylic acid with 3-O-(2′,3′-epoxy-propyl)-1,2:5,6-di-O-isopropylidene-α-d-glucofuranose. Another d-glucose oligomer was synthesized by the polycondensation of a dicarboxylic acid including the carbohydrate residue into the main polymeric chain, 3-O-benzyl-5,6-(bis-O-(acryloyloxy))-1,2-di-O-isopropylidene-α-d-glucofuranose, with propane-1,3-diol using p-toluenesulfonic acid as catalyst. These products were copolymerized with styrene and 2-hydroxypropyl methacrylate, respectively, at different mass ratios, using benzoyl peroxide as initiator. Differential scanning calorimetry was performed in order to study the copolymerization process of the monomer and oligomer into the chosen co-monomers, respectively, and the activation energy of this process was evaluated using Kissinger–Akahira–Sunose (KAS) method. The storage and loss modulus of the obtained glycopolymers were evaluated using dynamic mechanical analysis. The thermal stability of the obtained products was studied via thermogravimetry. 相似文献
4.
Bogdan?Ti?aEmail author Adriana?Fulia? Zoltan?Szabadai Gerlinde?Rusu Geza?Bandur Dumitru?Ti?a 《Journal of Thermal Analysis and Calorimetry》2011,105(2):517-527
The thermal techniques of analysis were used to assess the compatibility between ibuprofen (IB) and some excipients used in
the development of extended released formulations. This study is a part of a systematic study undertaken to find and optimizes
a general method of detecting the drug–excipient interactions, with the aim of predicting rapidly and assuring the long-term
stability of pharmaceutical product and speeding up its marketing. The thermal properties of IB and its physical association
as binary mixtures with some common excipients were evaluated by thermogravimetry/derivative thermogravimetry (TG/DTG) and
differential scanning calorimetry. FT-IR spectroscopy and X-ray powder diffraction (XRPD) were used as complementary techniques
to adequately implement and assist in interpretation of the thermal results. Based on their frequent use in preformulations
nine different excipients: starch; microcrystalline cellulose (PH 101 and PH 102); colloidal silicon dioxide; lactose (monohydrate
and anhydre); polyvinylpyrrolidone; magnesium stearate and talc were blended with IB. The samples were prepared by mixing
the analyte and excipients in a proportion of 1:1 (w:w). The TG/DSC curves of the IB have shown a single stage of mass loss
between 175 and 290 °C, respectively, an endothermic peak at 78.5 °C, which corresponds to the melting (literature T
m = 75–78 °C). 相似文献
5.
Capillary-HPLC-ESI-MS/MS method for the determination of acidic products from the oxidation of monoterpenes in atmospheric aerosol samples 总被引:1,自引:0,他引:1
A method is presented for the determination of acidic products from terpene oxidation in filter samples of the atmospheric
particle phase. Oxidation products of monoterpenes are believed to add a large fraction to the secondary organic aerosol (SOA)
in the troposphere. Those products with structures containing one or more carboxylic acid groups have especially low vapour
pressures and therefore they are believed to contribute substantially to the particle phase. Although many experiments were
performed in simulation chambers to study the SOA generation by oxidation of terpenes, concentration measurements of products
in the atmospheric particle phase are still rare. This is especially true for oxidation products of terpenes other than α- and β-pinene. Therefore, we developed a method for the quantification of acidic products from terpene oxidation in atmospheric
aerosol samples. After passing a PM 2.5 (PM = particulate matter) pre-separator to remove coarse particles, fine atmospheric
particles were collected onto quartz fibre filters. A backup filter was placed behind the first filter to estimate possible
sampling artifacts. The filters were extracted in an ultrasonic bath using methanol. After enrichment and re-dissolving in
water the samples were analysed using a capillary-HPLC-ESI(−)-MSn set-up. The ion trap mass spectrometer could be used to gain structural information about the analytes and to enhance the
selectivity of the measurements by using its MS/MS capability. A variety of products from different terpenes could be identified
and quantified in samples of the ambient atmosphere using reference data from chamber experiments. Due to strong matrix effects
quantification of samples from the real atmosphere had to be done by the standard addition method. 相似文献
6.
Hongwei Chen Rolf Brandt Rolf Bandur Thorsten Hoffmann 《Frontiers of Chemistry in China》2006,1(2):119-129
In this contribution, iodine chemistry in the Marine Boundary Layer (MBL) is introduced. A series of methodologies for the
measurements of iodine species in the gas and particle phases of the coastal atmosphere has been developed. Iodine species
in the gas phase in real air samples has been determined in two field campaigns at the west coast of Ireland, indicating that
gaseous iodo-hydrocarbons and elemental iodine are the precursors of new particle formation. Particulate iodine speciation
from the same measurement campaigns show that the non-water-soluble iodine compounds are the main iodine species during the
marine particle formation. A seaweed-chamber experiment was performed, indicating that gaseous I2 is one of the important precursors that lead to new particle formation in the presence of solar light in the ambient air
at the coastal tidal area. 相似文献
7.
Todea Anamaria Aparaschivei Diana Bîtcan Ioan Ledeți Ionuț Valentin Bandur Geza Péter Francisc Nagy Lajos Kéki Sándor Biró Emese 《Journal of Thermal Analysis and Calorimetry》2020,141(3):1017-1026
Journal of Thermal Analysis and Calorimetry - The thermal behavior of co-oligomers of ε-caprolactone (ECL) with gluconolactone, compared to the ε-caprolactone oligomer, has been assessed... 相似文献
8.
Ana-Maria Pan?Vasile Gherman Paula Sfîrloag?Geza Bandur Liliana-Marinela ?tefanMarcel Popa Lucian-Mircea Rusnac 《Polymer Testing》2012,31(3):384-392
This paper presents the thermal stability and biodegradability testing of new glycopolymers obtained by copolymerization of a novel D-mannose based oligomer with 2-hydroxypropyl acrylate and 2-hydroxypropyl methacrylate. The thermal analysis of these glycopolymers was investigated by thermogravimetry and the glass transition temperature was determined by DSC. While the acrylate derived glycopolymer has values of the glass transition temperature below 0 °C, the methacrylate derivative has positive values, above 50 °C. The biodegradation studies of the glycopolymers were carried out in a liquid medium, using pure cultures of two microorganisms, Zymomonasmobilis and Trichodermareesei. The weight losses of the new plastic materials were significant (almost 40%) and the best results were assessed for the 2-hydroxypropyl acrylate glycopolymer in the presence of both Z. mobilis and T. reesei. Microscopy showed that both microorganisms were present on the surface of the new glycopolymers and developed small colonies while modifying their surface. The changes inside the morphology of the polymeric materials structure were drastic and were studied via SEM analysis. 相似文献
9.
[structure: see text] An efficient total synthesis of the annonaceous acetogenin jimenezin was achieved. The key steps used were a highly stereoselective intramolecular allylboration to establish the tetrahydropyran ring and an intramolecular Williamson reaction to close the tetrahydrofuran ring. 相似文献
10.
N. I. Buryak V. A. Bandur V. N. Zavadovskaya D. F. Stepanishcheva 《Theoretical and Experimental Chemistry》1990,25(5):560-564
The structure of Ti(III) coordination polyhedrons in both individual NaPO3 and 70 mole % NaPO3-30 mole % NanX mixtures (X=PO3
3–, P2O7
4–, F–, Cl–) in the molten and solid states has been investigated on the basis of data from electronic absorption and ESR spectra. The formation of tetragonally distorted Ti(III) coordination polyhedrons with D4h symmetry coordinated only by (PO3
–)n chains with the following values of the spectroscopic parameters for the molten (and solid) states has been established in all the phosphate systems investigated: 10Dq=17,300 (18,000) cm–1 (Ds=50 cm–1, Dt=5600, g=1.959, g1=1.930, =93. cm–1). It has been shown that the greater is the extent of depolymerization of the phosphate chains in the melt, the stronger is the Ti(III) coordination polyhedron formed; the following relative series of the depolymerizing strength of the anions has accordingly been established: PO4
3–
2O7
4–