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Results w/Leading C18 Columns  The figure on the right shows a separation of guanidine under 100% aqueous conditions shown using C18 based on ordinary silica in reversed phase. Note the loss of retention after only about 10 injections of the analyte. This conventional column produced poor peak shape with low efficiency, with less retention than a Bidentate C18™ column shown below.
Click on the figure to see method conditions. |
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No loss of Retention on a Cogent C18 
The figures on the right shows a very good Separation of guanidine using the same method conditions above, 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 this column under very acidic mobile phase conditions, that would hydrolyze other reversed phases.
Click on the figure for more information
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Real Life Example: Guanidine 
These figures shows a real life cleaning validation sample for residual guanidine.
Upper chromatogram, standard at about 100 ppm, lower, a sample with a residue of about 10 ppm.
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