Determination of related impurities in a new active pharmaceutical ingredient – Sodium 4,4′-(propanediamido)dibenzoate

Abstract The new compound sodium 4,4′-(propanediamido)dibenzoate (malaben) exhibits pronounced activity in the treatment of non-alcoholic fatty liver disease, which could potentially allow it to be used as a drug. To study the content of related impurities in the malaben sample, conditions for electrophoretic separation were developed. The determination of impurities was carried out in a fused-silica capillary (length 60/50 cm × 50 μm i.d.) using a 50 mM borate buffer, at +20 kV voltage and a temperature of 25 °C, the hydrodynamic injection time was 7 s at a pressure of 30 mbar, with detection at 270 nm. Under these conditions, 4 related impurities were found, 2 of which were identified based on the synthesis scheme while the other 2 required structural elucidation. According to the obtained data on their electrophoretic behavior, the structures were approximately described. To identify the contaminants, HPLC-ESI/MS analysis conditions were developed. Separation was carried out on a Kromasil Zorbax 100–3.5 C18 column (150 × 2.1 mm), using an eluent of methanol and 0.05% formic acid solution with a flow of 0.2 ml min−1 at a column temperature of 40 °C and an injection volume of 20 μL. The structures of the 2 investigated impurities have been proven.