Thermal analysis | An-Najah Staff

Thermal Analysis Study of Flavonoid Solid Dispersions Having Enhanced Solubility

Tue, 2014-01-21 13:50 — Feras I. Qanaze

Journal Title, Volume, Page:

Journal of Thermal Analysis and Calorimetry, Volume 83, Issue 2, pp 283-290

Year of Publication:

2006

Link:

http://link.springer.com/article/10.1007%2Fs10973-005-6989-9

Authors:

F I Kanaze

Department of Pharmacy, School of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece, 54124

Current Affiliation:

Department of Pharmacy,Faculty of Medicine & Health Sciences, An-Najah National University, Nablus, Palestine

[email protected]

E Kokkalou

Department of Pharmacy, School of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece, 54124

I Niopas

Department of Pharmacy, School of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece, 54124

M Georgarakis

Department of Pharmacy, School of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece, 54124

A Stergiou

Applied Physics Laboratory, Department of Physics, Aristotle University of

D Bikiaris

Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, Greece, 54124

Preferred Abstract (Original):

Purposes of this paper were to prepare and study new drug delivery systems for both flavanone glycosides and their aglycones based on solid-dispersion systems. These compounds are poor water soluble drugs, so an enhancement of their dissolution is a high priority. Solid-dispersion systems were prepared using PVP, PEG and mannitol as drug carrier matrices. Characterizations of these dispersions were done by differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The glass transition (T g) temperature of PVP was only recorded in the DSC thermograms of PVP solid-dispersions of both flavanone glycosides and their aglycones, while in case of PEG and mannitol solid-dispersions endotherms of both glycosides and aglycones were noticed with low peak intensity, indicating that high percent of drug is in amorphous state. The XRD patterns of all PVP solid-dispersions of aglycones show typical amorphous materials, but XRD patterns of their glycosides reveal the presence of crystalline material. However, in all solid dispersions shifts in T gof PVP as well as T m of PEG were observed, indicating the existence of some interactions between drugs and matrices. SEM and TEM microscopy revealed that PVP/aglycone flavanone compounds are nanodispersed systems while all the other solid dispersions are microcrystalline dispersions. The solubility of both flavanone glycosides and their aglycones was directly affected by the new physical state of solid dispersions. Due to the amorphous drug state or nano-dispersions in PVP matrices, the solubility was enhanced and found to be 100% at pH 6.8 in the nano-dispersion containing 20 mass% of aglycones. Also solubility enhancement was occurred in solid dispersions of PEG and mannitol, but it was lower than that of PVP nano-dispersions due to the presence of the drug compounds in crystalline state in both matrices.

Physicochemical Studies on Solid Dispersions of ‎Poorly Water-Soluble Drugs: Evaluation of ‎Capabilities and Limitations of Thermal ‎Analysis Techniques

Mon, 2013-12-30 13:50 — Feras I. Qanaze

Journal Title, Volume, Page:

Thermochimica Acta Volume 439, Issues 1–2,Pages 58–67

Year of Publication:

2005

Link:

http://www.sciencedirect.com/science/article/pii/S0040603105004934

Authors:

Ferras Kanaze

Section of Pharmaceutics and Drug Control, Department of Pharmacy, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Macedonia, Greece

Current Affiliation:

Department of Pharmacy,Faculty of Medicine & Health Sciences, An-Najah National University, Nablus, Palestine

[email protected]

Dimitrios Bikiaris

Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece

Anagnostis Stergiou

Department of Physics, Aristotle University of Thessaloniki, 541 24, Thessaloniki, Greece

Eleni Pavlidou

Department of Physics, Aristotle University of Thessaloniki, 541 24, Thessaloniki, Greece

Evangelos Karavas

Pharmathen S.A., Pharmaceutical Industry, Dervenakion Str. 6, Pallini Attikis, 153 51 Attiki, Greece

Manolis Georgarakis

Section of Pharmaceutics and Drug Control, Department of Pharmacy, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Macedonia, Greece

Preferred Abstract (Original):

Polyvinylpyrrolidone (PVP) and poly(ethylene glycol) (PEG) solid dispersions with Felodipine or Hesperetin having up to 20 wt% drug were prepared using solvent evaporation method. Solid dispersions in comparison with their physical mixtures were studied using differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM) and hot stage polarizing light microscopy (HSM). PVP formulations with low drug load proved to be amorphous, since no crystalline Felodipine or Hesperetin drugs were detected using DSC and WAXD. Low and fast heating rates were applied for DSC study, to prevent changes in the samples caused during heating. Similarity between results of WAXD and DSC was also found in the case of physical mixtures, where the drug was in the crystalline state. However, though specific tests showed the high sensitivity of the DSC technique, it was difficult to arrive to reliable results for PEG solid dispersions or physical mixtures with low drug content by DSC, even by high heating rates. Crystalline drug could not be detected by DSC, leading to erroneous conclusions about the physical state of the drug, in contrast to WAXD. On the other hand, HSM proved the presence of small drug particles in the solid dispersions with PEG and the dissolution of the drug in the melt of PEG on heating. In such systems, in which a polymer with low melting point is used as drug carrier, DSC is inappropriate technique and must be used always in combination with HSM. The coupling of WAXD with thermal analysis, allowed complete physicochemical characterization and better understanding which is essential for a first prediction of dissolution characteristics of such formulations.

A Simplified Approach for Evaluating Plastic Axial and Moment Capacity Curves for Beam-Columns with Non-uniform Thermal Gradients

Mon, 2013-04-08 16:05 — Mahmoud M.S. Dwaikat

Journal Title, Volume, Page:

Engineering Structures, 32(5), pp.1423-1436

Year of Publication:

2010

Link:

http://www.sciencedirect.com/science/article/pii/S0141029610000222

Authors:

M.M.S Dwaikat

Department of Civil and Environmental Engineering, Michigan State University, United States

Current Affiliation:

Department of Civil Engineering, An-Najah National University, Palestine

[email protected]

VKR Kodur

Department of Civil and Environmental Engineering, Michigan State University, United States

Preferred Abstract (Original):

Restrained steel members, when exposed to fire develop significant forces and this transforms the behavior of a beam (or column) into that of a beam–column. The load carrying capacity of such beam–columns is determined through axial and moment capacity curves (P–MP–M curves). Codes and standards recommend the use of uniform average temperature for establishing the P–MP–M curves at elevated temperatures. This assumption, though adequate for cases where temperature in steel is uniform, such as a column exposed to fire from four sides, may not be valid for columns or beams exposed to fire from 1, 2, or 3 sides since significant thermal gradients develop across the section. These thermal gradients can cause severe distortion in the P–MP–M curves and render the capacity curves based on uniform temperature inadequate for evaluating the strength of such beam–columns. In this paper, a simplified approach is proposed for adjusting the uniform temperature plastic P–MP–M curves to account for the shape distortion resulting from fire-induced thermal gradients. The proposed method employs a two-step process in which the cross-sectional steel temperatures are calculated first, and then the distorted P–MP–M diagram is computed by adjusting the P–MP–M diagrams based on a uniform “averaged” temperature. The applicability of the proposed method to a design situation is illustrated through a numerical example. It is demonstrated that the proposed approach is well suited for predicting the capacity of beam–columns that develop thermal gradient under fire.

A simplified approach for predicting temperatures in fire exposed steel members

Mon, 2013-04-08 11:27 — Mahmoud M.S. Dwaikat

Journal Title, Volume, Page:

Fire Safety Journal

Year of Publication:

2013

Link:

http://www.sciencedirect.com/science/article/pii/S037971121200152X

Authors:

M.M.S. Dwaikat

Research Associate, Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI, United States

Current Affiliation:

Department of Civil Engineering, An-Najah National University, Palestine

[email protected]

V.K.R Kodur

Department of Civil and Environmental Engineering, Michigan State University, East Lansing, MI., United States

Preferred Abstract (Original):

For evaluating fire resistance of steel structural members, temperatures in the cross section of the member are required. In this paper, a simplified approach for evaluating cross sectional temperature in contour protected steel members exposed to fire is presented. The approach is derived utilizing simplifying assumptions to the general heat transfer equation for standard fire and is then extended for application under design fire scenarios. The proposed approach is applicable for both protected and unprotected steel sections. The validity of the approach is established by comparing predicted temperatures with those obtained from finite element analysis generated via ANSYS. In addition, predictions from the proposed method are also compared with the temperatures predicted by “best-fit” method. The comparisons to test data, finite element results and best-fit method indicate that the proposed simplified method gives good predictions of fire induced thermal gradient and temperature history in steel sections under any fire exposure. The simplicity of the proposed method makes it attractive for use in design situations.