As a mono-sodium salt form of alendronic acid,alendronate sodium presents multi-level ionization for the dissociation of its four hydroxyl groups.The dissociation constants of alendronate sodium were determined in thi...As a mono-sodium salt form of alendronic acid,alendronate sodium presents multi-level ionization for the dissociation of its four hydroxyl groups.The dissociation constants of alendronate sodium were determined in this work by studying the piecewise linear relationship between volume of titrant and p H value based on acidbase potentiometric titration reaction.The distribution curves of alendronate sodium were drawn according to the determined p Ka values.There were 4 dissociation constants(pKa_1=2.43,pKa_2=7.55,pKa_3=10.80,pKa_4=11.99,respectively) of alendronate sodium,and 12 existing forms,of which 4 could be ignored,existing in different p H environments.展开更多
The dissociation constants of polyepoxysuccinic acid(PESA)were investigated in this study.Based on the potentiometric titration and the BEST program,the dissociation constants of PESA were determined.Considering the c...The dissociation constants of polyepoxysuccinic acid(PESA)were investigated in this study.Based on the potentiometric titration and the BEST program,the dissociation constants of PESA were determined.Considering the complexity of the dissociation of PESA in aqueous solution,several models were constructed to simulate the dissociation process of PESA.By comparison,the dissociation constants of PESA were obtained with model 4.The species distribution of PESA in aqueous solution as a function of pH was also presented according to the experimental and calculation results.It showed that the H_(2)L model with five basic structure units to describe the dissociation of PESA was reasonable,and the relevant constants had less error and better matching between the experimental and calculation data.The corresponding values of pK_(ai) were 4.68 and 4.92,respectively,for H2L at 35℃ with ionic strength of 0.1 mol/L.展开更多
The emf of cell（A）without liquid junction was determined with 10%mass%urea-water mixed solvent in the temperature range 278.15-318.15K: Pt,H2（101.325KPa） HCl（ml）,H2SO4（m2）,urea（10%）-H2O AgCl-Ag Then,accordin...The emf of cell（A）without liquid junction was determined with 10%mass%urea-water mixed solvent in the temperature range 278.15-318.15K: Pt,H2（101.325KPa） HCl（ml）,H2SO4（m2）,urea（10%）-H2O AgCl-Ag Then,according to the emf data of cell,the second dissociation constant K2 of sulfuric acid in the mixed solvent was determined. The thermodynamic quatlities of the second dissociation process of sulfuric acid and the effect of solvent dielectric constant on K2 were discussed.展开更多
基金the support of Key Laboratory of Chinese Medicine Preparation of Solid Dispersion,Gansu Longshenrongfa Pharmaceutical Industry Co.,Ltd.,Gansu Province,China
文摘As a mono-sodium salt form of alendronic acid,alendronate sodium presents multi-level ionization for the dissociation of its four hydroxyl groups.The dissociation constants of alendronate sodium were determined in this work by studying the piecewise linear relationship between volume of titrant and p H value based on acidbase potentiometric titration reaction.The distribution curves of alendronate sodium were drawn according to the determined p Ka values.There were 4 dissociation constants(pKa_1=2.43,pKa_2=7.55,pKa_3=10.80,pKa_4=11.99,respectively) of alendronate sodium,and 12 existing forms,of which 4 could be ignored,existing in different p H environments.
基金This work was supported by the Key Technologies Research and Development Program of the Eleventh-Five Year Plan of China(Grant No.2006BAJ08B02)the Innovation Project of Talented Scientific Youth of Fujian Province in 2008 Year(No.2008F3096).
文摘The dissociation constants of polyepoxysuccinic acid(PESA)were investigated in this study.Based on the potentiometric titration and the BEST program,the dissociation constants of PESA were determined.Considering the complexity of the dissociation of PESA in aqueous solution,several models were constructed to simulate the dissociation process of PESA.By comparison,the dissociation constants of PESA were obtained with model 4.The species distribution of PESA in aqueous solution as a function of pH was also presented according to the experimental and calculation results.It showed that the H_(2)L model with five basic structure units to describe the dissociation of PESA was reasonable,and the relevant constants had less error and better matching between the experimental and calculation data.The corresponding values of pK_(ai) were 4.68 and 4.92,respectively,for H2L at 35℃ with ionic strength of 0.1 mol/L.
文摘The emf of cell（A）without liquid junction was determined with 10%mass%urea-water mixed solvent in the temperature range 278.15-318.15K: Pt,H2（101.325KPa） HCl（ml）,H2SO4（m2）,urea（10%）-H2O AgCl-Ag Then,according to the emf data of cell,the second dissociation constant K2 of sulfuric acid in the mixed solvent was determined. The thermodynamic quatlities of the second dissociation process of sulfuric acid and the effect of solvent dielectric constant on K2 were discussed.
