Authors:Yun-feng Liu, Jia-ling Zhang, Xue-fei Nie, Ping Zhang, Xiao-qing Yan, and Ke-feng Fu
food, pharmaceuticals, cosmetics, and so on. The esters of p -hydroxybenzoic acid (parabens) have become the most frequently used preservatives, due to their strong stability, low volatility, and low irritability [ 4 ]. Iodopropynyl butylcarbamate used
The aim of this paper is to review current applications for thermal methods within the pharmaceutical industry as well as
to present some early work on potential applications for two new thermal methods: Hi-Resolution Thermogravimetric Analysis
and Modulated Differential Scanning Calorimetry.
The existence of multiple crystal forms in a drug substance poses interesting development challenges as the material is taken
from discovery through formulation, manufacture and market. There are a number of factors why drug substances under development
are screened for presence of multiple crystal forms. Different crystal forms may exhibit varied performance properties including
bioavailability and solubility, as well as, differences in physical properties such as morphology and melting point. These
properties can affect the design of the manufacturing processes for the bulk drug substance, the formulation and the performance
of the drug product. This paper will focus on the application of differential scanning calorimetry (DSC) for the quantitation
of pharmaceutical crystal forms. Feasibility studies were conducted on several pharmaceutical drug substances which were known
to have multiple crystal forms, to determine if quantitative, semi-quantitative or limit of detection tests could be developed.
The conclusion from these studies is that polymorphic crystal systems comprised of either close, or melting with decomposing,
endotherms, competing transitions, or that contain sample contaminants, may not be optimum candidates for quantitation by
DSC. Conversely, crystal systems that contain polymorphs that exhibit well-resolved endothermic or exothermic transitions,
for either solvated vs. unsolvated species or both unsolvated, may be excellent candidates for crystal form quantitation by DSC.
Authors:Tuong Van Le Doan, Petr Stavárek, and Claude de Bellefon
A methodology that may be applied to help in the choice of a continuous reactor is proposed. In this methodology, the chemistry is first described through the use of eight simple criteria (rate, thermicity, deactivation, solubility, conversion, selectivity, viscosity, and catalyst). Then, each reactor type is also analyzed from their capability to answer each of these criteria. A final score is presented using “spider diagrams.” Lower surfaces indicate the best reactor choice. The methodology is exemplified with a model substrate nitrobenzene and a target pharmaceutical intermediate, N-methyl-4-nitrobenzenemethanesulphonamide, and for three different continuous reactors, i.e., stirred tank, fixed bed, and an advanced microstructured reactor. Comparison with the traditional batch reactor is also provided.
This article summarizes the different steps needed for a proper design and monitoring of the solid-state in pharmaceutical
industry in order to fulfill the requirements of the guideline dealing with polymorphism of the International Conference of
Authors:Elena Lizarraga, C. Zabaleta, and J. Palop
Thermal analysis of fusion and decomposition processes were carried out on recently synthetized pharmaceutical compounds in
order to establish thermal stability criteria. This study was carried out using thermogravimetry, TG, and differential scanning
calorimetry, DSC. Degradation and fusion temperatures have been produced as thermal data with the aim of to study the thermal
stability of the compounds.
Relationship is found among stability and a series of effects of structure of the compounds. The compounds which present an
amide functional group in the central molecule are more stable because they have a comparatively higher fusion and degradation
temperature. In addition, the stability of this type of compounds depends on the position of the electrophilic substitution
(in ortho, meta or para). Likewise, the groups linked to the aromatic ring with high electronic density give stability, and therefore are able to
delocalize the charge in a greater spacial interval.
Therefore, criteria for the selection of substituents have established that improve the stability of compounds
Authors:R. Ozao, M. Ochiai, Y. Ichimura, H. Takahashi, and T. Takano
The previously described method involving the use of transient DSC was applied to pharmaceutical powder compacts and to ceramic
powder compacts. The samples were prepared by compressing powders of pentaerythritol tetraacetate and two kinds of alumina
powder (differing in particle size distribution) up to a pressure of 20 MPa by using a jig. For pentaerythritol tetraacetate,
a linear relationship was obtained between the parameter obtained by DSC and the compaction pressure.
Modern thermal analysis, microcalorimetry and new emerging combined techniques which deliver calorimetric, microscopic and
spectroscopic data offer a powerful analytical battery for the study of pharmaceuticals. These techniques are very useful
in all steps of development of new drug products as well as methods for quality control in production. The characterization
of raw materials enables to understand the relationships between polymorphs, solvates and hydrates and to choose the proper
development of new drug products with very small amount of material in a very short time. Information on stability, purity
is valuable for new entities as well as for marketed drug substances from different suppliers. Excipients which vary from
single organic or inorganic entity to complexes matrixes or polymers need to be characterized and properly controlled. The
thermodynamic phase-diagrams are the basis of the studies of drug-excipients interactions. They are very useful for the development
of new delivery systems. A great number of new formulations need proper knowledge of the behaviour of the glass transition
temperature of the components. Semi-liquid systems, interactions in aqueous media are also successfully studied by these techniques.