How do I avoid distorted peak shapes when using a basic mobile phase pH for the analysis of a lipophilic amine - FAQ
July 5, 2018
/
/
/
/
/
/
/
/
/
/
/
You may not require a basic mobile phase pH for HPLC analysis of these types of analytes.
Use of the Cogent Diamond Hydride™ column in an Aqueous Normal Phase ANP method using with 0.1% formic acid instead of a basic mobile phase may be a better approach.
There are a number of possible reasons that you may have observed a distorted peak shape under the basic mobile phase conditions. Some possible explanations and their solutions are discussed here:
Use of the Cogent Diamond Hydride™ column in an Aqueous Normal Phase ANP method using with 0.1% formic acid instead of a basic mobile phase may be a better approach.
There are a number of possible reasons that you may have observed a distorted peak shape under the basic mobile phase conditions. Some possible explanations and their solutions are discussed here:
- The column might be overloaded. This could be due to an excessive sample concentration or too large of an injection volume. Typically injection volumes of 1 to 5 microliters are appropriate. If that is the amount you were injecting, then try diluting the sample some to see if that resolves the problem.
- The sample diluent may not be appropriate. If there is a mismatch between the diluent and the mobile phase, distortion of the peak can occur. In most cases, a sample solvent of 50:50 of the mobile phase components is suitable. For example, 50:50 acetonitrile / water both with 0.1% formic acid.
- The peak shape may be able to be improved with an ANP gradient with 0.1% formic acid. Try starting off with a linear gradient going from 95% B to 30% B over a time frame of 10 minutes. Once you have an idea of the retention and resolution under these conditions, then you can adjust the gradient for better separation and resolution.