On this page we inspect the HPS™ C18 retention maps shown on the left revealing fairly predictable retention profiles for standard traditional phases such as HPS C18. Here we see that Uracil not retained at 10% organic mobile phase content, Pyridine is only retained in basic conditions but Phenol is noted to behave more like a neutral compound with retention at both extremes of pH (shown).

If we look at the Cogent UDC-cholesterol™ retention maps shown here, it reveals quite unexpected results to even experienced chromatographers only aware of irregular, type A or type B silica based HPLC phases. When viewed with our previously gained TYPE-C™ phase Retention Map knowledge, the results are totally predictable for a the UDC-Cholesterol phase and other TYPE-C™ based phases although they are quite unique.

Continued assessment of the UDC-Cholesterol retention maps further reveals that Pyridine (basic compound) elutes in Aqueous Normal Phase (ANP) order while in acidic conditions. Phenol, as it does with typical type B phase (HPS C18) is behaving largely as a neutral compound while it is interesting to note that Uracil can be retained ANP at both extremes of pH.

Combining this knowledge of using pH and percentage acetonitrile/water gives the user the orthogonal options of having various elution orders on the same column for the same peaks. For example you could elute compounds similar in nature to Uracil as a traditional type B Aqueous Reverse Phase (ARP) would, then Pyridine then Phenol would follow. Phenol, Uracil then Pyridine as an elution order is also possible, as is infinite ANP retention of Pyridine as is shown on this page.