Voltammetric and spectrophotometric studies of toxic disinfection by-product 2,6-dichloro-1,4-benzoquinone and its behavior with DNA

Water disinfection processes may generate several dangerous substances that can affect both human beings and the environment. As a known contaminant in drinking water, the compound 2,6-dichloro-1,4-benzoquinone (DCBQ) and its degradation products in aqueous solution are of continuing concern regarding environmental, biomedical, and technical applications. There is great interest in the development of analytical methods capable of elucidating the mechanisms of the interactions of DCBQ and its degradation products with the nucleic acids of living organisms. Here, a systematic voltammetric study employing a glassy carbon electrode was performed, for the first time, to investigate the redox properties of DCBQ and its interactions with double-stranded DNA (dsDNA). The DCBQ has a reversible process at pH range from 3.70 to 12.60 and pH-dependent until pH 9.20, resulting in the formation of a reversible oxidation product in a pH-dependent system to pH 6.00 at a glassy carbon electrode. By varying incubation time and pH of electrolyte solutions, DCBQ showed spontaneous degradation which was presented by the change of its electrochemical behavior in solution. The spontaneously degraded DCBQ underwent a reversible and pH-dependent process for 3.70 <= pH <= 6.00. By spectrophotometry experiments, the spontaneous decomposition of DCBQ in aqueous solution was verified. DCBQ interacted indirectly with dsDNA and its degradation product(s) interacted with the deoxyguanosine homopolynucleotide with release of guanine and adenine from the double helix, but no oxidative damage to the dsDNA by DCBQ or its product(s) was detected.