Physicochemical characterization melting point

Chemical development Proof of structure and configuration are required as part of the information on chemical development. The methods used at batch release should be validated to guarantee the identity and purity of the substance. It should be established whether a drug produced as a racemate is a true racemate or a conglomerate by investigating physical parameters such as melting point, solubility and crystal properties. The physicochemical properties of the drug substance should be characterized, e.g. crystallinity, polymorphism and rate of dissolution. 

In the solid state, the form of the drug will affect both its solubility and its physicochemical stability. A full characterization of the drug in the solid state will often include a determination of the melting point and heat of fusion using differential... 

There are a number of interrelated thermal analytical techniques that can be used to characterize the salts and the polymorphs of candidate drugs. The melting point of a salt can be manipulated to produce compounds with desirable physicochemical properties for specific formulation t5q)es. Of the thermal methods available for investigating polymorphism and related phenomena, DSC, TGA, and HSM are the most widely used methods. 

The preparation of salts is frequently undertaken to improve the physicochemical properties of an ionizable compound. Most often, improvement of solubility and dissolution rate is desired. However, improvement in crystallinity (e.g., melting point), stability, or hygro-scopicity may be possible (1,2). Figure 18.1 shows the solubility of several salts of terfena-dine and the free base as a function of pH. Development of salts, particularly soluble salts of insoluble compounds, is not without challenge, however. Complete characterization of salt forms is needed (4). If the salt is very soluble, precipitation of the insoluble free base (or free acid) may occur in uivo under physiological pH conditions. 

Cocoa fat and lipids In AOAC methodologies, the composition of fat and fatty acids in cocoa fat extracts are analyzed and characterized by physicochemical methods, including refractive index, melting point, saponification value and unsaponifi-able material, iodine number, Reichert-Meissl and Polenske values. 

Physicochemical characterization Physicochemical characterization yields a number of important parameters that can be used in the control of the quality of a substance. Typical properties are melting point and other thermal data, solubility, acid-base behavior with pfCa values, redox potentials, polymorphism, and spectral information. Other property-influencing parameters are choice of counterion and salification studies. 

The most common crystalline forms are polymorphs, hydrates, and solvates (pseudopolymorphs). Polymorphs are formed when a substance crystallizes in two or more crystal structures. Polymorphism significantly impacts on physicochemical properties of materials, such as stability, density, melting point, solubility, bioavailability, and so on. Hence the characterization of all possible polymorphs, identifying the stable (thermodynamic) polymorph, and design of reliable processes for consistent production are critical in modem day drug development. 

Overall, the characterization of the melt agglomeration end point using the biexponential mathematical model is simple and without the need to consider the physicochemical properties of the processing materials used. As the process of agglomeration is aimed at making highly spherical pellets, predictive methods based on sphericity will help to capture the ideal end point together with predictive methods based on size. 

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