The partition coefficients of p-nitrophenol between 0.05N HCl and CHCl3 were measured with or without tri-O-methyl-β-cyclodextrin (methyl-β-CD) at 15.5, 20.0, and 25.0°C. The partition coefficients increased linearly with methyl-β-CD concentration. In the presence of 3.00×10-2M methyl-β-CD, the value was about 2.5 times larger than that measured in the absence of methyl-β-CD. Methyl-β-CD was not detected in the aqueous phase by polarimetry, and most of the methyl-β-CD molecules were present in the CHCl3 phase. The increase of the partition coefficients can be interpreted in terms of 1 : 1 complex formation between methyl-β-CD and p-nitrophenol. The complexes of methyl-β-CD and p-nitrophenol in the aqueous solution and the CHCl3 solution were studied quantitatively by ultraviolet absorption measurements. The formation of inclusion complex in D2O was also investigated by proton magnetic resonance spectroscopy.
