Problem of sorption equilibrium in a migrating chromatographic zone

1 Problem of sorption equilibrium in a migrating chromatographic zone 

The longitudinal concentration profile of the zone in the column is usually not known, but the time course of the solute concentration in the effluent can be detected by a detector at the column outlet. In such a record the retention time of the center of gravity (first statistical moment) of the detected peak [28] corresponds to the retention time of the concentration maximum of the real zone. However, in most cases of linear chromatography these two retention times are practically identical, i.e. the retention times of the center of gravity and of the maximum of the peak detected are also identical. 

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