Effect of furosemide on micellar behaviour of ionic surfactants - A physicochemical approach

Abstract

Micellar solubilization of drug Furosemide at concentrations 0.001 M and 0.01 M in surfactants: sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) has been carried out by measuring different transport properties. Conductance measurements of anionic surfactant SDS and cationic surfactant CTAB have been measured in solutions of aqueous Furosemide at above said concentrations in the temperature range 293 to 313 K. From these measurements, critical micelle concentrations, CMC’s of SDS and CTAB have been determined in these solutions. From CMC data, various thermodynamic parameters viz. standard Gibbs free energy, Δ<i>G<img src='http://www.niscair.res.in/jinfo/subscript8.gif' border=0></i> enthalpy, Δ<i>H<img src='http://www.niscair.res.in/jinfo/subscript8.gif' border=0></i> and entropy of micellization, Δ<i>S<img src='http://www.niscair.res.in/jinfo/subscript8.gif' border=0></i> have been evaluated. The negative Δ<i>H<img src='http://www.niscair.res.in/jinfo/subscript8.gif' border=0></i> and positive Δ<i>S<img src='http://www.niscair.res.in/jinfo/subscript8.gif' border=0></i> values for these systems suggest the contribution due to electrostatic interactions in addition to hydrophobic interactions. There is also an indication that the micellization tends to be energy driven process at higher temperature. Enthalpy- Entropy compensation is also presented to calculate compensation temperature T_c. In addition, sound velocity and density measurements have been carried out at all temperatures and used to calculate the isentropic compressibility, <i>K_s</i> apparent molar volume, <i>φ_v</i> and apparent molar adiabatic compressibility, <i>φ_k</i>. The results obtained from these studies are supported by spectrophotometric techniques i.e. UV/visible and Fluorescence spectroscopy. All these parameters provide insight in terms of drug – surfactant interactions as a consequence of various electrostatic and hydrophobic interactions. Further the results show that the micellization of SDS becomes highly cooperative in comparison to CTAB in the presence of Furosemide. Another important conclusion drawn from these studies is that at lower concentration of Furosemide, the CMC value of SDS is increased considerably whereas in case of CTAB an opposite effect has been observed.