The addition of deuterium oxide or organic solvents to surfactant‐based electrolytes is an effective method for improving resolution in micellar electrokinetic capillary chromatography (MECC). Buffers containing phosphate, boric acid and sodium dodecyl sulphate at pH or pD 7 in the presence and absence of deuterated and non‐deuterated solvents were used to separate some hydrophobic compounds covering a range of octanol‐water partition coefficients (log P). Significant improvements in resolution of the more hydrophobic compounds were achieved by using mixtures of heavy water and deuterated methanol, instead of water and methanol. Quantitative structure‐retention relationships were also derived to provide a better understanding of the intermolecular interactions that contribute to the separation of analytes in MECC. Multiple regression analysis has shown that capacity factors were significantly related to both log P and molecular refractivity. The latter is a measure of the molecular volume of analytes and is related to their ability to undergo dispersive interactions with the micellar components.