Voltammetric study of the interaction of the ofloxacin–copper complex with DNA, and its analytical application

The electrochemical behavior of the ofloxacin–copper complex, Cu(II)L₂, at a mercury electrode, and the interaction of DNA with the complex have been investigated. The experiments indicate that the electrode reaction of Cu(II)L₂ is an irreversible surface electrochemical reaction and that the reactant is of adsorbed character. In the presence of DNA, the formation of the electrochemically non-active complexes Cu(II)L₂-DNA, results in the decrease of the peak current of Cu(II)L₂. Based on the electrochemical behavior of the Cu(II)L₂ with DNA, binding by electrostatic interaction is suggested and a new method for determining nucleic acid is proposed. Under the optimum conditions, the decrease of the peak current is in proportional to the concentration of nucleic acids in the range from 3 × 10⁻⁸ to 3 × 10⁻⁶ g · mL⁻¹ for calf thymus DNA, from 1.6 × 10⁻⁸ to 9.0 × 10⁻⁷ g · mL⁻¹ for fish sperm DNA, and from 3.3 × 10⁻⁸ to 5.5 × 10⁻⁷ g · mL⁻¹ for yeast RNA. The detection limits are 3.3 × 10⁻⁹, 6.7 × 10⁻⁹ and 8.0 × 10⁻⁹ g · mL⁻¹, respectively. The method exhibits good recovery and high sensitivity in synthetic samples and in real samples.