I need to dissolve a sodium alginate gel crosslinked with calcium carbonate to release an embedded drug for HPLC analysis.

Following the literature, I first attempted using a sodium citrate solution at a 20:1 molar ratio relative to calcium ions (20 moles of sodium citrate per 1 mole of Ca²⁺), followed by filtration with a 0.45 µm pore size filter.

However, the resulting solution exhibited a retention time that did not match the expected retention time of the drug.

Has anyone encountered a similar issue?