Separation and determination of D-malic acid enantiomer by reversed-phase liquid chromatography after derivatization with (R)-1-(1-naphthyl) ethylamine

Abstract

L-Malic acid is the Active Pharmaceutical Ingredient of the latest generation of compound electrolyte injection (STEROFUNDIN ISO, Germany) and plays a very important role in the rescue of critically ill patients. The optical purity of L-malic acid is a Critical Quality Attributes. A new reversed-phase high performance liquid chromatography (RP-HPLC) method for pre-column derivatization of D-malic acid enantiomer impurity in L-malic acid bulk drug was established. The derivatization reaction was carried out using (R)-1-(1-naphthyl)ethylamine ((R)-NEA) as a chiral derivatization reagent. The Kromasil C₁₈ column was used with a detection wavelength of 225 nm, a flow rate of 1.0 mL·min^-1, and a column temperature of 30 °C. The mobile phase was acetonitrile-0.01 mol·L^-1 potassium dihydrogen phosphate solution (containing 20 mmol·L^-1 sodium heptanesulfonate, adjusted to pH 2.80 with phosphoric acid) (at a ratio of 45:55) and the resolution of D-malic acid and L-malic acid derivatization products reached 1.7. The proposed method possesses the advantages of simple operation, mild conditions, stable derivatization products and low cost. Also it gave better separation and was more accurate than previous methods.

Keywords:
L-Malic acid; (R)-NEA; Chiral purity; Pre-column derivatization