In the first chromatogram for these compounds separated on the Cogent UDC-Cholesterol column shown on the left hand side this page, Phenol, Uracil and then Pyridine are seen eluting in their ANP order when the mobile phase is in a basic pH of 8.00 as previously shown. Instinctively, most chromatographers would assume that Uracil is not retained and is on the solvent front at 95% acetonitrile, but in fact Uracil is the second peak of this chromatogram. Phenol is the compound that is still on solvent front. The Pyridine peak is seen as slightly tailing and the peak in the final elution order. If the acid pH retention map was shown on this page, it could be seen that Pyridine could have been retained longer, even infinitely as the acetonitrile concentration is raised, but the tailing would have been increasingly worse.

In the chromatogram in the middle of this page, the analysis of neutrals at acid pH, reveals the UDC-Cholesterol phase working ARP with four well resolved, symmetrical, sharp Neutral peaks.

In the third chromatogram (farthest on the right) the acid pH for the acid target compounds also reveals another ARP analysis, with the three acids compounds being the last three well resolved, symmetrical, sharp peaks.

This page shows that you choose the separation mechanism to utilize, ARP / ANP / ONP depending on your target compounds, but you additionally have the potential to differentiate them if unknown target compounds behave in a predominantly, neutral / acid or base target compound dependent on it’s Type C elution profile. The potential also exists to retain acids and bases differentially in high acetonitrile percentages at appropriate pH’s and then elute non retained neutral plus opposite form, and finally use a organic or pH gradient to resolve the retained form of ionic compound. The non-retained form can then be retained at the opposite pH extreme and separated from the neutral and the above process repeated. Finally ARP could resolve the un-retained neutrals on the same Type C phase.

This unique ability could be useful for complex mixtures of various types of unknowns such as bioactive natural products etc.