Discuss the following effect on the retention time (increase, decrease, remain the same or become zero) of a peak in a liquid chromatography: (i) (ii) (iii) (iv) Raising the column temperature, Decreasing the particle size of the column material (at constant pressure), Having bubble formed in the column, Increasing the column head pressure.
In column chromatography, a stationary phase and a mobile phase are used to separate the components in a sample. Liquid mobile phase containing these components come in contact with stationary phase and interact with it in different way. Stationary phase is also called as resin. Retention time is defined as the particular time spent by each component of sample inside the column. Each component has different retention time depending on its chemical properties.
(i) Raising the column temperature, the interaction between mobile phase containing components and the stationary phase increases. So the components are separated at a faster rate. Hence the sample spends less time inside the column. So the retention time decreases.
(ii) If the size of the components decreases, it will pass through the pores of resin/silica bed at a faster rate. So the separation time decreases. So it in turns decreases the retention time.
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