Basics of Chromatography:

The analytical scientists all around the world got actively engaged within improving the participating phases, detectors and the instrumentation in common. In 1959, a technique known as gel filtration chromatography to separate high and low molecular weight substances, originated at Biochemical Institute in Uppsala, Sweden. In the 1960s, further improvements in the conventional liquid chromatography led to the development of high performance liquid chromatography. The following decade of the seventies saw an important improvement in adsorption chromatography in the form of affinity chromatography which was mainly based on biological interactions. The researches for developments in chromatography were still being carried out and a new type of chromatography using superficial fluids appeared on the scene. Supercritical fluid chromatography is a hybrid of gas and liquid chromatography and combines the advantageous features of the two.

The above description on the growth of chromatography clearly points out that once the potential of some simpler versions of chromatography for separations was realized, the researches took place on a phenomenal pace. It will not be wrong to say that the entire twentieth century can be named as the century of chromatography. Even today, the efforts are being made to bring different types of improvements. At this point, one should not forget that the developments are not only because of variety of physicochemical  principles that can be incorporated in chromatographic techniques to bring out separations, but are partly due to the compelling need of the scientific community to achieve a variety of tedious separations particularly related with life sciences.

The present unit aims at proposing a classification of chromatographic techniques. An effort will also be made to explain some of the general principles which lead to separation of compounds present in a mixture. Before discussing the theory or the concepts, it may be necessary to familiarize you with the terms which are used to assess the separation efficiency of a process.

Objectives

After studying this Unit, you should be able to

• Describe the different ways chromatographic techniques can be classified,
• Elaborates processes taking place during elution on columns,
• Realize the importance of words like migration rate, distribution constant, retention factor, retention time, selectivity factor and resolution,
• Elaborates the concept of theoretical plates and its importance, and
• Define the rate theory.