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Do I need to use a high mobile phase pH for compounds with a high pKa?

Reference Number: AA-01249 Created: 02/25/2013 02:50 PM Last Updated: 07/23/2016 12:21 PM

No, while some types of analyses for compounds have traditionally required a high mobile phase pH (e.g. up to 10, 11 or 12) in order to get acceptable chromatographic retention due to a high pKa, it is no longer necessary to use high pH to get retention. These extreme conditions can be damaging to any HPLC system's pump seals, tubing, joints and detection cells. Also, at very high pH and moderate ionic strength, you can expect column problems due to silica dissolution issues.

Using Cogent™ TYPE-C™ HPLC columns and Aqueous Normal Phase (ANP), a high mobile phase pH may not be required. Many types of compounds can be retained readily in the typical usable HPLC pH range of 2-7. It should be noted that some methods call for high pH due to solubility of the analytes. If this is the case, you would want to stay with high pH.

This is one of the many advantages of Cogent™ columns for polar compound analysis. 

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