Deoxyribonucleic acid (DNA) is an important hereditary substance in humans and in almost all other living organisms. It plays a vital role in the storage of genetic information and instructs the biological synthesis of proteins and enzymes through the process of replication and transcription of heritage information Thus, the identification and quantification of either individual and/or group of purine and pyrimidine bases are important for diagnosis of certain diseases and genetic disorders. Though there exits quite a few methods for such sensing, there is a great demand for a cheap, sensitive and interference free electrode for simultaneous determination of all the four neuclobases due to their important role in medical diagnosis, crime detection and biocomputing.

In the present work, an efficient electrochemical sensor has been fabricated for simultaneous determination of purine bases adenine (AD), guanine (GU) and pyrimidines bases thymine (TY), cytosine (CY) using Cu doped CeO₂ nanoparticles modified glassy carbon electrode (Cu-CeO₂/GCE). Direct electrocatalytic activities of DNA bases have been studied in phosphate buffer solution (PBS, pH 7.0) without any enzyme using voltammetric techniques. 3 wt% Cu doped CeO₂ modified GCE showed two well defined anodic peaks each corresponding to the oxidation of purine (AD, GU) and pyrimidine (TY, CY) bases with significant peak to peak potential separation of 312 mV (AD-GU) and 200 mV (TY-CY) which were large enough for the selective and simultaneous determination of these bases in their mixture. Under optimum conditions, calibration plots for the simultaneous detection of the purine and pyrimidine bases were linear in the concentration range of 0.1– 500 μM for AD, 1–650 μM for GU, 1-300 μM for TY and 1-250 for CY with detection limit values of 0.021, 0.031, 0.024 and 0.038 μM respectively. Additionally the developed sensor exhibited good repeatability, reproducibility, sufficient stability and good anti-interference ability and was successfully applied for simultaneous detection of AD, GU, TY and CY in denatured DNA sample with satisfactory results.

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