Bivariate retention

When both the swamping electrolyte and the IPR concentrations are varied, the retention is correctly described by a bivariate expression [59], The relationship predicts that the capacity factor of a solute oppositely (similarly) charged to the IPR decreases (increases) with increasing ionic strength, because of the lower net electrostatic attractive (repulsive) potential. The predictions are experimentally verified [59]. Again, it is epistemologically interesting to observe that the retention equation, in the absence of the IPR in the eluent, reduces to that developed and tested in RP-HPLC... 

A bivariate treatment of the simultaneous effects of IIR mobile-phase concentration and organic modifier percentage in the eluent on analyte retention gives the following relationship ... 

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