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In this work, a polymeric brilliant cresyl blue (BCB) and dihexadecyl phosphate (DHP) dispersed Multi-walled carbon nanotubes (MWNTs) composite film modified glass carbon electrode (PBCB-MWNTs-DHP/GCE) denoted as epinephrine (EP) sensor was prepared by an in-situ electropolymerization method. The electrochemical response of EP at the sensor is much better. Voltammetric investigations indicated that the improved response of EP at the sensor mainly arose from the enhanced adsorption of EP at PBCB-MWNTs-DHP film, perhaps through the hydrogen bonding and p -p interactions between EP and PBCB. The sensor was applied to the determination of EP in injection by a standard addition method and the results were satisfied. Brilliant cresyl blue (BCB), a phenoxazine dye, could be electropolymerized on the GCE in different pH solutions [17]. Only a few works have been reported about the application of the poly (brilliant cresyl blue) (PBCB) [18]. In this work, the in situ electropolymerization of BCBMWNTs-DHP composite was performed at a GCE. PBCB-MWNTs-DHP film was proved to apparently improve the electrochemical response of EP. Based on this, a sensitive and selective electrochemical method for the determination of EP was proposed, which was successfully applied to the determination of EP in injection samples. KeywordsThe electrochemical responses of 5.0 Â 10 À6 M EP at different electrodes such as bare GCE, MWNTs-DHP/ GCE, PBCB/MWNTs-DHP/GCE and EP sensor in 0.1 M PBS (pH 6.0) have been investigated. The experimental results prove that EP sensor produces the best response towards the oxidation of EP. The in situ electropolymerization for the surface functionalization of CNTs has several advantages: it can reduce the usage of modifier, produce more uniform composites and make full use of the whole composite films, especially the inner layers, which is essential to the achievement of high signal-to-noise ratio and sensitivity.The surface morphology of different films is characterized by SEM. As shown in Figure 1, many nanoparticles were observed on both the MWNTs-DHP film (Fig. 1a) and the PBCB-MWNTs-DHP film (Fig. 1b), however, the PBCBMWNTs-DHP film is more compact and uniform because of the covering of thin PBCB film on the nanotubes. The PBCB-MWNTs-DHP film has plenty of nanopores that allow the free entry of substrates.The solution pH was found to significantly influence the electrochemical response of EP at the sensor (Fig. 2). In the range of pH 3.0 to 9.0, the oxidation peak current of EP firstly increases up to pH 6.0 and then decreases by contraries (Fig. 2, insert a). Similarly, the oxidation peak potential positively shifts up to pH 5.0 and then shifts to the negative direction (Fig. 2, insert b), moreover, the oxidation peak potential has a good linear relationship with the pH value in the range of 5.0 to 9.0 [E p (V) ¼ 0.49 þ 0.046 pH], which shows that the number of proton and transfer electron are 1143

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