Quality Control of L-Ascorbic Acid 2-Phosphate Magnesium Using Reversed-Phase Liquid Chromatography

L-Ascorbic acid 2-phosphate magnesium (AP-Mg) salt is a Vitamin C derivative frequently used as a raw material in cell culture media for research purposes as well as for Good Manufacturing Practice (GMP)-manufacturing of cell and tissue advanced therapy medicinal products. A selective reversed-phase HPLC (RP-LC) method was developed and validated. Commercially available AP-Mg products from different suppliers were analyzed. Various new impurities were found using this newly developed RP-LC method. Using quantitative nuclear magnetic resonance spectroscopy, a mass balance of roughly 99.9% was obtained; the total numbers of impurities detected in both methods are also identical. The values of the relative ultraviolet (UV) response factors at λ = 210 nm of the impurities in this RP-LC method were discussed. When equaling the overall mean relative response factor of the impurities to 0.6 (estimated central value), the mass balance in the RP-LC method was nearly 100%. The structures of the new impurities are proposed as ethylation derivatives of open-ring AP-Mg products as well as phosphorylated derivatives of ascorbic acid.