A dopamine sensor based on a methoxypolyethylene glycol polymer covalently modified glassy carbon electrode

A dopamine (DA) sensor based on a methoxypolyethylene glycol (MPEG) polymer covalently modified glass carbon electrode (GCE) was fabricated by an electroadsorption method. The electrochemical behavior of the sensor towards the catalytic oxidation of DA in pH 5.0 phosphate buffer solution (PBS) was investigated by cyclic voltammetry. The modified electrode obviously enhanced the current response and decreased the overpotentials for the oxidation of DA. Using differential pulse voltammetry, the sensor gave a linear response to DA over the concentration range of 2.0-140 μM with a detection limit (S/N = 3) of 4.68 × 10(-8) M. It was found that MPEG can complex DA through hydrogen bonding interaction between ethylene oxide units of the polymer and the protonated dopamine in acidic PBS and preconcentrate it in the film, which improved the detection limit and sensitivity of DA. The DA sensor exhibits good sensitivity, selectivity and stability, and has been applied for the determination of DA in dopamine hydrochloride injection solution.