A new potentiometric sensor based on a high-performance composite for nanomolar determination of mercury (II) in environmental samples

A new potentiometric sensor for the rapid determination of Hg2+ based on modified carbon paste electrode consisting of room temperature ionic liquid, 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6), multi-walled carbon nanotubes (MWCNTs), alumina nanoparticles and a synthetic macrocyclic diamide '7,10,13-triaza-1-thia-4,16-dioxa-6,14-dioxo- 2,3;17,18-dinaphtho-cyclooctadecane' as an efficient ionophore was constructed. Prepared composite is an ideal paste because it has low drift of potential, high selectivity and fast response time (10 s), which leads to a more stable potential signal. The morphology and properties of electrodes surface were characterised by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy. A linear dynamic range of 2.01-2.01 x 10(7) mu g L-1 with detection limit of 1.40 mu g L-1 Hg2+ was obtained at pH range of 2.5 to 4.5. The prepared modified electrode shows several advantages such as simple preparation method, high stability of the composite paste, high sensitivity, long-term life time (at least 13 weeks) and remarkable potentiometric reproducibility. The modified electrode was successfully applied for the accurate determination of trace amounts of Hg (2+) in environmental samples.