HPLC Determination of Rhychophylline and Isorhychophylline in Uncaria with Ionic Liquid as Mobile Phase Additive

HPLC was applied to the determination of rhychophylline and isorhychophylline in uncaria with ionic liquid as mobile phase additive. The uncaria sample (0.532 g) was extracted ultrasonically with 60% (φ) methanol solution (10 mL) for 30 min at 25℃. After filtration,subsequent filtrate was collected. C₁₈ chromatographic column was used as stationary phase, and buffer solution of 16.7 mmol·L^-1 KH₂PO₄ (pH 3.0, 20 mmol·L^-1HMIM BF₄ ionic liquid used as additive) was used as mobile phase. UV-detection at 245 nm was adopted in the determination. Linear relationships between values of peak area and mass concentration of rhychophylline and isorhychophylline were kept in the same range of 1.56-100 mg·L^-1, with detection limits (3S/N) of 0.914, 0.194 mg·L^-1, respectively. The proposed method was applied to the analysis of the sample of uncaria, giving values of recovery and RSD's (n=6) in the ranges of 98.0%-101% and 0.60%-1.8%, respectively.