With Cogent TYPE-C HPLC columns, it is unlikely that Reversed Phase (RP) and Aqueous Normal Phase (ANP) retention contributions would be equal for different amphiphilic compounds under the same conditions. It would require that both mechanisms be operating at equal efficiency for those particular compounds under the same method conditions. 

In most cases, one mechanism would be more dominant than the other and retention mechanisms for different compounds would be different. However, even in the unlikely event that both were equal this would only occur at one mobile phase composition and would change with changes in the mobile phase concentrations or gradients.  

You could switch to a different isocratic composition or a different gradient and that could shift the relative contributions of your compounds with the two different mechanism working for separation.

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