Transport processes pharmaceutical applications

Pikal, M.J. Heat and mass transfer in low pressure gases application to freeze-drying. In Transport Processes in Pharmaceutical Systems, pp. 611-686, edited by G.L. Amidon, P.I. Lee, E.M. Topp. Marcel Dekker, New York, 2000... 

Aqueous solvents are the most common in pharmaceutical and, of course, in biological systems, so this chapter is concerned mainly with solutions of aqueous and mixed aqueous solvents, such as alcohol-water mixtures. The solution of dmgs in nonaqueous media (such as oils) is also considered because of the many pharmaceutical applications of nonaqueous solutions and formulations such as oil-in-water emulsions, and because of the need to understand the process of the transport of... 

Safety and hygiene effects. Limitations related to process/product safety can in some cases be solved by the use of microstructured reactors. For example, very exothermic reactions and explosive gas mbctures have been demonstrated to operate safely in structured reactors [12]. The transport of hazardous chemicals could also find sustainable solutions in the development of distributed production in miniaturized plants [13]. In the frame of product engineering, micromixers allowed the quantity of emulsifiers and preservatives required to stabilize emulsions for pharmaceutical applications to be reduced [14]. 

The study of diffusion processes of electrolytes and non-electrolytes in aqueous solutions is important for fundamental reasons, helping to imderstand the nature of aqueous electrolyte stmcture, for practical applications in fields such as corrosion, and provide transport data necessary to model diffusion in pharmaceutical applications. Although no theory on diffusion in electrolyte or non-electrolyte solutions is capable of giving generally reliable data onO, there are, however, estimating pmposes, whose data, when compared with the experimental values, will allow us to take off conclusions on the nature of the system. 

Porphyrin-modified electrodes were widely utilized for quantification of low concentrations of metals, pharmaceutical products, and species of environmental and industrial importance in association with flow techniques. This strategy enhances the amperometric response and sensitivity (the capacitive current is virtually reset), while reducing significantly the time necessary for analyses. Flow injection analysis (FIA) has been extensively explored for this purpose and a revision on the application of porphyrins and derivatives was published some years ago [203]. Alternatively, batch injection analysis (BIA) can be an interesting way for fast analyses utilizing a similar mass transport process to the electrode surface [204]. For example, citric acid was electrochemically determined by BIA using cobalt phthalocyanine modified carbon paste electrodes [205]. 

Where small quantities of high-purity steam is required for electronic chip, pharmaceutical, sterilization, food preparation, and similar process applications, a small risk of steam contamination may exist. This may be caused directly by the use of amine treatments or indirectly through process contaminants or the transport of iron oxides. Consequently, alternative arrangements for steam generation are made. 

The use of SCB as media for diemical reactions has increased during the past few years, as discussed in the next sectioiL The large partial molar volumes of solutes near the critical point result in unusualty large volumes of activation and large variations of certain reaction rate constants and selectivities with pressure. The following section on rate processes desolbes relatively novel crystallization processes that have commercial promise and transport properties in SCFs. The last two sections disr a variety of food, pharmaceutical, and environmental applications and provide an in-depth treatment of the design of commercial plants. 

Many processes in pharmaceutics are related to transport, and the appHcations of the outlined theory are therefore numerous. Notwithstanding their practical importance, the special instances of the general transport equation (11) listed in Table 2 are assumed to be relatively familiar, and will therefore not be discussed further in this chapter. Instead, we focus our attention on applications of hereditary integrals and linear response theory, in particular on dynamic mechanical analysis (DMA) and impedance spectroscopy. 

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