Authors:Satya Girish Avula, Kenneth Alexander, and Alan Riga
A eutectic is formed from a mixture of two or more solids and has a melting point lower than that of each of its constituents. It is generally represented by a phase diagram where the liquid and solid phases impact upon each other with a value known as the eutectic point. In pharmaceuticals, poor water solubility is a major obstacle for releasing new dosage forms into the market. Eutectic formation overcomes these problems. Preparation of a phase diagram by Differential Scanning Calorimetry can determine eutectic properties, but it is tedious. A modified Van't Hoff (VH) equation was used in this study. Devalina Law developed a dimensionless index for the VH equation. The difference in melting points of an excipient polymer and drug are divided by the slope of the VH equation. In previous studies, five excipient–drug compositions were evaluated. The final index relationship was in good agreement except for the salt, quinine sulfate. In order to test the validity of the VH index, further studies of PEG with acetylsalicylic acid, acetaminophen, diflunisal, dimenhydrinate, ketoconazole, and mefenamic acid were performed.
Authors:Amanda Santos, Gilberto Chierice, Kenneth Alexander, Alan Riga, and Ellen Matthews
Eugenol is the main volatile compound extracted oil from clove bud, Syzygiumaromaticum L., and used in traditional medicine, as a bactericide, fungicide, anesthetic, and others. Its extraction was performed using
hydrodistillation which is the most common extraction technique. Its components and thermal behavior were evaluated using
gas chromatography (GC) and differential scanning calorimetry (DSC), which provide a better characterization of these natural
compounds. This extracted product was compared to the standard eugenol results. The GC results suggested ~90% eugenol was
found in the total extracted oil, and some of its boiling characteristics were 270.1 °C for peak temperature and 244.1 J g−1 for the enthalpy variation.
Authors:Cheila G. Mothé, Michelle G. Mothé, Alan T. Riga, and Kenneth S. Alexander
Thermal properties of some shedded snake skins in comparison with human skins are represented by thermogravimetry (TG), derivative thermogravimetry (DTG), and differential thermal analysis (DTA) to predict process condition as dermal pathway for administration of drugs or it be used as model membranes for permeation studies. Thermal behavior by TG/DTG and DTA curves for four kinds of shedded snake skins as Boelens Python (BP), Eastern Indigo Snake (EIS), Emerald Tree Boa (ETB), and Cascavel (CBR) were similar in relation to their decomposition temperatures at 100 °C and 230–400 °C of its constituents, however, their properties were different in the residue content (inorganic or carbonaceous substances). Similar thermal properties were also exhibited by human skins’ samples, however, they presented different residue and constituents’ content.
Authors:Visweswararao Badipatla, Dean Pohlman, Manik Pavan Maheswaram, Dhruthiman Mantheni, Naullage Indika Perera, Martin Mittleman, Kenneth Alexander, and Alan Riga
The current United States Pharmacopeia (USP) test for the disintegration of drug tablets does not measure initial disintegration times and does not adequately describe tablet disintegration mechanisms. An Isothermal Mechanical Analysis (IsoTMA) method meeting USP specifications has been developed to measure the initial time and rate of drug disintegration. TMA monitors the physical dimension of the formulated drug tablet as a function of time, temperature, applied stress, and pH. TMA can be used to measure the swelling, shrinkage, or disintegration of a formulated tablet in a specified fluid. The focus of this study is to validate an efficient and precise IsoTMA method to measure dimensional stability of solid dose tablets. The precision of the method along with the effect of pH (1–10) and temperature (25–37 °C) on the rate of delivery was determined for nine drugs. Graphical representations of dimensional changes over time were created and compared. Drug delivery in a specific liquid medium was measured by UV analysis for the active pharmaceutical ingredient. An increase in temperature decreased the disintegration time and increased the disintegration rate (mm/min). For the drugs that are studied in this article, pH did not have an appreciable effect on the rate of disintegration.
Authors:Lakshmi Kaza, Hany F. Sobhi, Jeffrey A. Fruscella, Chris Kaul, Shravan Thakur, Naullage I. Perera, Kenneth Alexander, and Alan T. Riga
A standard protocol was developed to determine the water content by thermal analysis of milk of magnesia (MoM). Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used in a novel manner for examining the physical characteristics of the commercial pharmaceutical suspensions. Moisture analyzer and oven-dry methods validate the proposed protocol. MoM consists primarily of water and magnesium hydroxide [Mg(OH)2]. Experimental design of the thermal analysis parameters were considered including sample size, flowing atmosphere, sample pan, and heating rate for both DSC and TG. The results established the optimum conditions for minimizing heat and mass transfer effect. Sample sizes used were: (5–15 mg) for DSC and (30–50 mg) for TG. DSC analysis used crimped crucibles with a pinhole, which allowed maximum resolution and gave well-defined mass (water) loss. TG analysis used a heating rate of 10 °C/min−1 in an atmosphere of nitrogen. The heat of crystallization, heat of fusion, and heat of vaporization of unbound water are 334, 334, and 2,257 Jg−1, respectively (Mitra et al. Proc NATAS Annu Conf Therm Anal Appl 30:203–208, ). The DSC average water content of (MoM) was 80 wt% for name brand and 89.5 wt% for generic brand, based on the relative crystallization, melting and vaporization heats/Jg−1 of distilled water in the recently purchased (2011) MoM samples. The TG showed a two-step process, losing water at 80–135 °C for unbound water and bound water (MgO·H2O) at 376–404 °C, yielding a total average water loss of 91.9 % for name brand and 90.7 % for generic brand by mass. The difference between the high-temperature TG and the lower-temperature DSC can be attributed for the decomposition of magnesium hydroxide or MgO·H2O. Therefore in performing this new approach to water analysis by heating to a high temperature decomposed the magnesium hydroxide residue. It was determined that the TG method was the most accurate for determining bound and unbound water.