The present unit gives an introduction to the course on separation methods. It highlights the utility of separations within the analysis and recovery of pure products from complex mixtures. The scope of separations extends from the requirements of everyday life to complex technological processes. There is hardly any branch of science or technology that has not been a beneficiary of the developments in separation science. Separations encompass variant physicochemical principles and the subject has it matured to a unified science. Many of the well known methods of separations fall under the types of chromatographic methods.
It is a little hard task to categorize the variety of separation methods available present days. A simpler classification could be made on the basis of property that results within separation. The other approach which can be adopted for categorization is based on the physicochemical phenomena responsible for separation. Alternatively, these phenomena could be divided under two categories, the equilibrium and the rate processes. In equilibrium processes, there have to be two competing phases. Therefore, in rate processes, the constituents move differently by a permeable barrier or display different migration velocities under several fields, major electrical.
In both the categorization, it has been possible to categorized most of the well known separation methods in one or the other category. But a few of the methods are such which they could be put in more than one category.
As regards the criteria to be used for the assessment of utility of a separation method, the overall problem is situation based. This point can be clarified through the fact in which the selection or the utility of a method will be determined through the physical state of the mixture, its complexity, and amount of sample available, the speed needed and the level of purity desired. It has to be kept in mind in which whether the method is to be used for analysis or synthesis/recovery. But this only does not necessarily decide the importance of the different criteria cited in the text.