[Interactions of surfactants with model and biological membranes. XXII. Spectrophotometric determination of partition coefficient of heptacaine, a local anesthetic, between the phospholipid liposome and water phase].

The partition coefficient of the local anaesthetic heptacaine (monohydrochloride of [2-(heptaloxy)phenyl]-2-(1-piperidinyl)ethyl ester of carbamic acid) between unilamellar liposomes prepared from chromatographically pure egg yolk phosphatidylcholine and the aqueous phase (NaCl solution, ionic strength I = 0,1,pH 4,5, temperature t = 20 degrees C) was determined using UV-VIS spectrophotometry. The contribution to the anaesthetic spectra due to light scattering on liposomes was eliminated numerically using the scattering function. This procedure gave more precise results than the subtraction of liposomes spectra. The values of the partition coefficient defined with the use of molar concentrations, weight concentrations and molar fractions estimated at a wavelength of lambda = 292 nm were Kp = 1116 +/- 49, Kp(m) = 1098 +/- 48 and Kp(x) = 47575 +/- 2089, respectively.