The influence of water-ethanol mixture composition on the complex formation between 18-crown-6 ether and L-phenylalanine was studied by titration calorimetry at T = 298.15 K. The standard thermodynamic parameters (Lambda(r)G(o), Lambda H-r(o), T Lambda S-r(o)) of formation of [Phe18C6] molecular complex were calculated from data obtained by means of the microcalorimetric system TAM III (TA Instruments, USA) at X(EtOH) = 0.0/0.6 mol fraction. The stability of [Phe18C6] and the mechanism of complexation in water were investigated using the H-1 and C-13 NMR spectroscopy. The increase of EtOH concentration results in an increase of the complex stability and of the exothermicity of complexation. (C) 2012 Elsevier B.V. All rights reserved.