HPLC Determination of Lactic Acid Monomers in Poly L-Lactic Acid

HPLC was applied to the determination of residual amount of lactic acid monomer in the pharmaceutical adjuvant poly L-lactic acid. The optimized chromatographic conditions obtained by orthogonal test were as follow: a mixture of methanol and 0.1 mol·L-1 KH2PO4 solution, mixed in the ratio of 5 to 95 was used as mobile phase, with a flow-rate of 0.8 mL·min-1 and at the column temperature of 40 ℃. Linear relationship between values of peak height and mass concentration of lactic acid was kept in the range of 2.00-100 mg·L-1, with detection limit (3S/N) of 0.50 mg·L-1. Tests for recovery and precision were made, giving results of average recovery of 96% and RSD (n=6) of 2.0% respectively.