Consuming products that contain Ba2+ ions may cause some problems to human health such as hypopotassaemia, gastroenteritis, changes in nerve reflexes, muscle weakness and cardiac arrhythmias [1-3]. Therefore, because of the pollution growth as a result of these activities, it is necessary to develop sensitive and selective techniques to detect and quantify Ba2+ ions. The electrochemical methods are more suitable for this purpose due to good properties such as high selectivity and sensitivity, being less time consuming and inexpensive. In this work, carmoisine (CA) was applied as a new electroactive label for Ba2+ electrochemical detection at the surface of DNA-based carbon paste electrode modified with Ag-rGO nanocomposite as genosensor using differential pulse voltammetry (DPV). The performance of the biosensor has been evaluated, as well as its applicability to the analysis of real samples. The peak current of CA increased with increasing of Ba2+ ions concentration and the DNA-based sensor showed linear ranges of 0.06-0.80 nM and 1.0-80 nM and a limit of detection (LOD) of 0.045 nM (Figure 1) . Fig. 1: A) DPV curves of 10−3 M accumulated CA on the G4/Ag-rGO/ CPE in 50 mM Tris–HCl buffer solution (pH=7.4) containing various concentrations of Ba2+: (a) 0.0, (b) 0.06, (c) 0.1, (d) 0.2, (e) 0.4, (f) 0.6 , (g) 0.8, (h) 1.0, (i) 5.0, (j) 10.0, (k) 20.0, (l) 30.0, (m) 40.0, (n) 50.0, (o) 60.0 and (p) 80.0 nM. (B) The difference of cathodic peaks current in the absence and presence of Ba2+ ions (ΔI) in the differential pulse voltammograms (A) against the Ba2+ concentrations. Inset shows the related calibration plots of Ba2+ concentrations in the ranges (a) 0.06 –0.8 nM and (b) 1–80 nM.
