Study on Hydrolysis Reaction of Novel Camptothecin Derivative(L-P) Using Capillary Zone Electrophoresis / 分析化学

ABSTRACT

Capillary zone electrophoresis (CZE) was developed to investigate the structure stability of novel camptothecin derivative (L-P) at different pH,the kinetics and thermodynamics of hydrolysis reaction from lactone form to carboxylate form direction at near physiological conditions (pH 7.4,310 K). Uncoated fused-silica capillaries(35 cm×50 μm i. d,with effective length of 26.5 cm) were used. The background electro-lyte( BGE) was 0.025 mol/L sodium phosphate buffer with pH varied at 2.5,4.0,5.0,6.0,7.0,7.4 and 9. 0. The electrophoresis voltage was maintained at 14 kV when the pH of BGE ranged between 2.5 and 5.0,otherwise,the voltage was maintained at 10 kV. The UV detector was set at 260 nm. All samples were introduced using hydrodynamic injection at 5 kPa for 4 s. L-P was found to be lactone form as the solution pH was below 4. 0. As pH increased,the lactone form of L-P would undergo hydrolysis reaction to be carboxylate form. As pH was 9.0,L-P existed almost completely as carboxylate form. The rate constant of the hydrolysis increased as temperature raise. The energy of activation ( Ea) ,the enthalpy ( ΔH) and entropy (ΔS) of the hydrolysis reaction were determined as 72. 6 kJ/mol,10. 5 kJ/mol and 50. 9 J/( mol K) ,respectively. The proposed capillary zone electrophoresis could efficiently separate two pH-dependent structural forms of the novel camptothecin derivative( L-P). The positive enthalpy and entropy values of the L-P hydrolysis indicated that the reaction was endothermic and entropically driven and higher temperature favored.