Morphine is a powerful opioid pain medication and commonly used narcotic pain killer and is toxic during overdose or when abused. Compared to conventional analytical techniques, the electroanalytical method has significant advantages viz. low cost, simplicity, ease of operation and facile miniaturization. In the present paper different approaches based on various modifications adopted for effective electrochemical sensing of morphine are reviewed in a comprehensive way. Among different modified electrodes available for the detection of morphine, carbon based materials—CNTs and graphene—display effective quantification and are attractive in terms of cost compared to noble metals. In addition, the performance of reported sensors in terms of their including detection range (LDR), limit of detection (LOD) and technique used are presented. The present review compares various electroanalytical techniques adopted for the determination of morphine.

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The unique properties of graphene blended with palladium deposition were used for sensing application by virtue of its charge transfer properties. Epinephrine (EP) is anodically oxidized on a glassy carbon electrode (GCE) modified by palladium graphene composite in phosphate buffer solution of pH 7. The electrodeposited palladium over the GCE -graphene surface ensures fast electrochemical determination of EP. The electrode served as a sensing platform for the simultaneous voltammetric determination of EP, ascorbic acid (AA) and uric acid (UA). The electrochemical deposition of palladium has greatly enhanced the surface properties. Cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry were used to assess the electrochemical performance. Investigations reveal that the process is adsorption controlled involving two electrons and the average catalytic rate constant is 2.39 × 10 3 M −1 s −1 . Palladium incorporated electrode sensitively determined EP in presence of the usual interferents uric acid (UA) and ascorbic acid (AA) with well resolved peaks at very minute concentrations. DPV method enabled the highest sensitivity of 100nM for EP, 170nM for UA and 22μM for AA. The modified electrode offered excellent performance toward real samples such as blood serum and urine.

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