Affinity chromatography basic components

The rate of elution of a component of the mixture is determined by the relative affinities of the component for the stationary and mobile phases. In gas chromatography, the elution rate is most often expressed as a retention time, defined as the time between the placement of the sample on the column and the maximum elution of the component in question. The basic principle responsible for the great utility of all chromatographic methods is the same Even compounds with very similar structural features frequently are eluted from the column at sufficiently different rates that an analytical or preparative separation is possible. If the efficiency of a gas chromatographic column is expressed in theoretical plates for comparison with distillation (Sec. 2.4.1), it is found that the gas chromatographic column provides 50 times as many theoretical plates as an efficient distillation column (e.g., a spinning-band column) of the same length. 

---