title: pKa determination of oxysophocarpine by reversed - phase high performance liquid chromatography.
abstract: BACKGROUND
  In this study, a RP - HPLC method was applied for determination of pKa value by using the dependence of the capacity factor (k) on the pH of the mobile phase for oxysophocarpine (OSP).
  
  
  RESULTS
  The effect of the mobile phase composition on the ionization constant was studied by measuring the pKa value at different MeOH concentrations, ranging from 10 to 20% (v/v). Based on all pH - k curves plotted and pH values at inflection point calculated, experimental pKa value obtained for oxysophocarpine was 6.5.
  
  
  CONCLUSIONS
  This method was successfully applied to realize low sample consumption, rapid sample throughput, high sensitivity and precision.
authors.affiliation: College of Chinese Traditional Medicine, Guangzhou University of Traditional Chinese Medicine, 232 East of Waihuan Road, University Town, Guangzhou, Guangdong 510006 R.P. China ; College of Chinese Traditional Medicine, Southern Medical University, Guangzhou, Guangdong 510515 R.P. China.
authors.forename: Huiling
authors.initials: H
authors.lastname: Huo
authors.forename: Tingting
authors.initials: T
authors.lastname: Li
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
keywords: HPLC; Oxysophocarpine; pKa value