Bioequivalence and Bioavailability Forum

Dear all,
We are developing am HPLC/MS method to measure omeprazole enantiomers in human plasma.

So far, we have tried two column brands but were not lucky with any of them.
The first brand (Phenomenex Lux) showed lack of robustness: when switching from one column batch to another there was a shift in retention times, changes in resolution between enantiomer peaks and a significant decrease in the slope of the calibration curve. With one particular column we even had a lack of linearity in the calibration curve range.

So we decided to try another brand, hoping for consistency in results. We decided to try a Chiralpack IC-3, based on published data.
We employed chromatographic conditions as per recommendations of the manufacturer of the column and resolution between peaks was ok when using standard solutions (without plasma). But, as soon as we injected the calibration curve in plasma, the peaks did not resolve at all.

The manufacturer claims that the column was not meant to be used with plasma samples. But, in this particular case, plasma samples were cleaned-up by SPE extraction prior to injection, and only 11 injections of plasma samples were performed!

So we think that there is a problem with this column in particular.

Does anyone have any experience (good/bad) with chiral columns?

Any suggestions are welcomed. Chiral columns are very expensive and it has been very frustrating not to be able to find a suitable one.

Thank you very much!

Lyn