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Figure 1: Separation of guanidine under conditions shown using C18 based on ordinary silica in reversed phase. Note the loss
of retention after only about 10 injections. This conventional column produced poor peak shape with low efficiency, with less
retention than a Bidentate C18™ column used in reversed phase.
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Figure 2: Above shows a separation of guanidine using the same method conditions, but with a Cogent Bidentate C18™
(L1 column). The upper chromatogram is the initial separation, and the lower after 2 days of use with over 100 injections. No changes
in retention were observed. Note the excellent stability of the type C phase under very acidic mobile phase conditions that would
hydrolyze other reversed phases. See next page for conditions.
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Many highly polar compounds require 100% Aqueous Mobile Phases to be retained in Reverse Phase. With columns manufactured with
ordinary silica, loss of retention over time due to the hydrophobic nature of the columns occurs. Specialty columns such as
polar-embedded phases are used. Although loss of retention may be solved, equilibrating these columns can take a long time. Using
the Cogent Bidentate C18 column which is made with silica hydride, loss of retention does not occur even with hundreds of
injections. Below is an example of one method for Guanidine that shows two columns in 100% Aqueous mobile phase.
