Determination of azelaic and sorbic acid in pharmaceduticals by capillary electrophoresis

Capillary electrophoresis with indirect UV detection at 254 nm was applied to simultaneous determination of ∼20% of azelaic acid and ∼0.1% of sorbic acid in AKNOREN cream. The acids were separated in fused silica capillary (45 cm × 50 μm) at 30 kV. Optimised back-ground electrolyte was 30 mM benzoate buffer (pH∼6, adjusted with TRIS) containing 7 mM β-cyclodextrin and 5% of methanol; internal standard was 2-hydroxysobutyric acid (HIBA). Rectilinear calibration ranges were 0.4–4 mg mL−1 for azelaic acid and 2–20 μg mL−1 for sorbic acid and the recoveries were 97.2–100.5%. A single analysis took <15 min.