We have tried a medronic acid based gradient additive with initial success. The peak shape of succinic acid in a HILIC separation greatly improved from terrible to acceptable. This showed us that the poor peak shape was indeed due to metal chelation. Succinic acid was the only peak that was affected. So far so good….

However, we have begun noticing that the calibration curves for nearly all substances, negative and positive mode, are now upward-facing quadratics rather than nice straight lines as they were before. We have noticed this effect at the prescribed 1 mL/L (5uM) dosing but also even at 100 uL/L (500nM). This indicates ion suppression imo.

Has anyone else had experiences with medronic acid additives to the mobile phase - positive or negative? I would be curious.