A comparison of high speed differential scanning calorimetry (Hyper-DSC) and modulated differential scanning calorimetry to detect the glass transition of polyvinylpyrrolidone: the effect of water content and detection sensitivity in powder mixtures (a model formulation)

Pharmaceutical cocrystals, salts and polymorphs: Advanced characterization techniques

The main goal of a novel drug development is to obtain it with optimal physiochemical, pharmaceutical and biological properties. Pharmaceutical companies and scientists modify active pharmaceutical ingredients (APIs), which often are cocrystals, salts or carefully selected polymorphs, to improve the properties of a parent drug. To find the best form of a drug, various advanced characterization methods should be used. In this review, we have described such analytical methods, dedicated to solid drug forms. Thus, diffraction, spectroscopic, thermal and also pharmaceutical characterization methods are discussed. They all are necessary to study a solid API in its intrinsic complexity from bulk down to the molecular level, gain information on its structure, properties, purity and possible transformations, and make the characterization efficient, comprehensive and complete. Furthermore, these methods can be used to monitor and investigate physical processes, involved in the drug development, in situ and in real time. The main aim of this paper is to gather information on the current advancements in the analytical methods and highlight their pharmaceutical relevance.

Methods to characterize the structure of food powders – a review

Food powders can exist in amorphous, crystalline or mixed structure depending on the order of molecular arrangement in the powder particle matrices. In food production, the structure of powders has a greatly effect on their stability, functionality, and applicability. The undesirable structure of powders can be accidentally formed during production. Therefore, characterization of powder structure as well as quantification of amorphous–crystalline proportions presenting in the powders are essential to control the quality of products during storage and further processing. For these purposes, many analytical techniques with large differences in the degree of selectivity and sensitivity have been developed. In this review, differences in the structure of food powders are described with a focus being placed on applications of amorphous powders. Essentially, applicability of common analytical techniques including X-ray, microscopic, vapor adsorption, thermal, and spectroscopic approaches for quantitative and qualitative structural characterization of food powders is also discussed.

Fast-Scan DSC and its role in pharmaceutical physical form characterisation and selection

Conventional rate Differential Scanning Calorimetry (DSC) has been used for many years as a tool in the analysis of pharmaceutical materials. In recent years an extension of the technique to include fast heating and cooling rates has become more prevalent. Broadly termed Fast-Scan DSC, this review examines the current applications of this technique to the characterisation and selection of pharmaceutical materials. Its increasing use encompasses the characterisation of amorphousness in crystalline materials, the characterisation of polymorphs and polymorphic transitions, the solubility of drugs in polymers, and characterisation of dosage forms. Notwithstanding the advantages of analytical speed in analytical turnover, the review emphasises the advantages of Fast-Scan DSC in its sensitivity which allows the separation of overlapping thermal events, the reduction it provides in degradation during the scanning process and its role in determining solubility in waxy and polymeric based systems. A comparison of the uses of Fast-Scan DSC to modulated DSC techniques and localised thermal analysis is also given.

HyperDSC studies of amorphous polyvinylpyrrolidone in a model wet granulation system

Measurements of the properties of amorphous materials are very important to help in the understanding of how materials behave during manufacture, storage and use of medicines. However, there are few methods that are suited to the study of amorphous materials, especially if in multi-component systems or model formulations. The goal here was to explore the potential for the use of HyperDSC to study a model granulation system. It was found that the sensitivity of HyperDSC was such that the glass transition (Tg) of polyvinylpyrrolidone (PVP) could be detected in granules made with realistic levels of this binder. The measured Tg in the granules, even after drying, was very different to that of PVP alone and to PVP in physical mixtures with lactose. It is argued that the granulation process has resulted in the dissolution of some lactose and that the amorphous binder holding the granules together is in fact a solid dispersion of PVP and lactose. Based on the standard Gordon-Taylor equation it was estimated that the solid dispersion contained 50% of PVP and lactose. Given that solid dispersions have a tendency to crystallise on storage, it could be expected that changes in the binder properties will occur with time after granulation. We believe that this is the first measurement of in situ properties of a binder in this way and opens the possibility of studies on formulated systems.