Study of local anaesthetics: part 201. Determination of the critical micellar concentration of pentacaine hydrochloride from the measurements of UV absorption of pyrene in methanol solutions.

The formation of micelles of the local anaesthetic pentacaine hydrochloride (K 1902) in methanol solutions at two concentrations was investigated by measuring the absorbance of pyrene in surfactant solution. The absorbance vs. surfactant concentration profiles for all the major UV spectral peaks of pyrene have been found to be sigmoidal in nature which were analyzed according to Sigmoidal-Boltzmann equation to evaluate the cmcs values of the studied systems. The influence of the methanol concentration on the critical micellar concentration was studied. The observed critical micellar concentration rises with an increasing of alcohol.