Poly(malachite green) films were synthesized electrochemically on the glassy carbon electrode in the potentiodynamic mode. The characterization and growth mechanism of as-prepared films were studied with FT-IR spectroscopy, UV-vis spectroscopy, cyclic voltammetry, chronocoulometry, and electrochemical impedance spectroscopy. Charge transfer and ion transport of poly(malachite green) films were investigated in the aqueous solutions with different types of supporting electrolytes. The poly(malachite green) film coated glassy carbon electrode showed catalytic ability towards ascorbic acid and dopamine. The difference of the anodic peak potential of ascorbic acid on the poly(malachite green) film modified electrode from that of dopamine was 180 mV. Based on their voltammetric responses, the poly(malachite green) film coated glassy carbon electrode was utilized as an electrochemical sensor for the content determination of ascorbic acid and dopamine simultaneously and separately in pharmaceutical and injections. (c) 2006 Elsevier Ltd. All rights reserved.