Background: Parabens are derivatives of synthetic esters of p-hydroxybenzoic acid, which due to their biocide activity, have found extensive applications in food products, pharmaceuticals and cosmetics as chemical preservatives [1]. Due to the widespread uses of parabens as preservatives in various industries, development of appropriate analytical methods for determining parabens in different matrices is necessary. The electroanalytical techniques, especially electrochemical sensors [2-4], are alternatives for detection of parabens in real samples. Herein, an electrochemical sensor based on a bilayer composite of phosphomolybdate doped polypyrrole (PPy-PMo12) and nanodiamond (ND) at a disposable gold chip (GCHIP) has been introduced for detection of propylparaben (PP). Methods: Voltammetry experiments were carried out using an Electroanalyzer system with a conventional home-made glass electrochemical cell and a three-electrode configuration. Results: In order to obtain the optimization condition, the amount of ND, dopant concentration, the scan rate and the pH of buffer solutions were investigated. To evaluate the electrocatalytic activity of the proposed modified electrode, cyclic voltammograms of PP oxidation at the GCHIP, ND/GCHIP, PPy-PMo12/GCHIP and PPy-PMo12/ND/GCHIP modified electrodes were recorded in a solution of Britton-Robinson buffer (pH 7.00) containing 200 μmol L-1 of PP. To evaluate the sensing performance of the proposed electrode, LSV technique was employed to construct a calibration curve under the optimum conditions. The linear range 5-200 μmol L-1 and limit of detection 2.1 μmol L-1 was obtained. In order to evaluate the applicability of the proposed PP sensor for real sample, a commercial shampoo product was subjected to the analysis and satisfactory recoveries were obtained. Conclusion: In this work, a bilayer composite composed of PMo12/PPy organic-inorganic hybrid material electrodeposited on a pre-casted ND film at a disposable GCHIP has been employed for construction of a disposable PP electrochemical sensor. The obtained PPy-PMo12/ND/GCHIP showed favorable electrical conductivity and increased electrocatalytic activity for PP oxidation due to the synergistic effects.

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