Study of local anesthetics. Part 123: HPLC study of pentacaine, heptacaine and carbisocaine.

A relationship between the capacity factor k' of pentacaine, heptacaine and carbisocaine and mobile phase composition (content of methanol and water, ionic strength and pH) has been studied by HPLC. It has been found that there is a linear relationship between log k' and the content of methanol in the mobile phase in the range 80-100% (vol) of methanol. The ionic strength of solute also has an influence on log k'. When the amount of solute is higher than 0.25 mol/l, than its influence on log k' is not important. The pH = pK inflection point of sigmoidal dependence k' = f(pH) can be found.