▎ 摘　　要

A simple, sensitive and selective electrochemical method was developed for the simultaneous determination of morphine and codeine using a carbon paste electrode (CPE) modified with a Zn2SnO4-graphene nano composite by differential-pulse voltammetry (DPV). The Zn2SnO4-graphene nanocomposite was prepared via a facile and simple process. The resulting composite was characterized by scanning electron microscopy, X-ray diffraction, thermogravimetric analysis and electrochemical impedance spectroscopy. The prepared nanocomposite modified CPE showed enhanced peak currents for the oxidation of morphine and codeine as compared to those of graphene/CPE, Zn2SnO4/CPE and the bare CPE. The analytical curves for the simultaneous determination of morphine and codeine showed an excellent linear response, ranging from 0.020-15 mu mol L-1 for both of them. The detection limits for determining morphine and codeine were 0.011 and 0.0090 mu mol L-1, respectively. No significant interference was seen for some interfering compounds such as Ca2+, glucose, lactose, sucrose, ascorbic acid, acetaminophen, ethanol, noscapine and others in the detection of analytes. The proposed method was successfully applied for the simultaneous and individual determination of these analytes in human body fluids and pharmaceutical samples.