A novel ionic liquid, 4-hydroxy-1-methyl-[1-(3-pyrrolyl-propyl)]-piperidinium bromide, was synthesized and characterized. Carboxylic-functionalized graphene oxide nanosheets were modified with this ionic liquid to fabricate a nanocomposite which was denoted as GrO-COO-IL. Characterizations of FTIR, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy confirmed the successful conjunction of these two components. GrO-COO-IL nanocomposites were homogeneously dispersed with utralpure water, and were then coated onto glassy carbon electrode surface. Followed by cyclic voltammetric scanning, a graphene oxide-polymerized ionic liquid film modified electrode (GrO-COO-Poly-IL/GCE) was prepared, and was studied with electrochemical impedance spectroscopy and scanning electron microscope. It was found that both honokiol and magnolol exhibit sensitive voltammetric response at the GrO-COO-Poly-IL/GCE. Simultaneous assay of honokiol and magnolol was realized with differential pulse voltametry. In the presence of magnolol, the oxidation peak current was linearly related to honokiol concentration in the range of 1.0 x 10(-8) similar to 1.0 x 10(-5) mol L-1 with a detection limit of 1.53 x 10(-9) mol L-1 (S/N = 3). Meanwhile, in the presence of honokiol, a linear relationship between the oxidation peak current and magnolol concentration was found from 7.0 x 10(-8) to 1.0 x 10(-5) mol L-1. The detection limit is calculated to be 8.27 x 10(-9) mol L-1 (S/N = 3). In addition, GrO-COO- Poly-IL/GCE was successfully used for determination of honokiol in the traditional Chinese medicine, and was demonstrated to be an effective and sensitive method. (C) 2014 Elsevier Ltd. All rights reserved.