Chemically Modified Multiwalled Carbon Nanotubes as Efficient Material for Construction of New Al(III) Ion Selective Carbon Paste Electrode

A selective potentiometric ion-selective electrode for the determination of aluminium ion (Al³⁺) in aqueous solution based on incorporation of 2-((3-silylpropylimino) methyl) phenol in carbon paste matrices has been reported. For modification of the electrode response, the influence of multiwalled carbon nanotubes (MWCNTs) amount is investigated to improve conductivity and transduction of chemical signal to electrical signal. It is found that incorporation of MWCNTs at optimum composition of carbon paste (graphite powder: NaTPB: Nujol: carrier in the mass (mg) ratio of 150/9.0/40.0/100) significantly enhanced selectivity and sensitivity toward Al³⁺ ions over a wide concentration range of 1.0×10^-7 to 5.0 × 10^-2 mol L^-1 with detection limit of 8.5 × 10^-8 mol L^-1 and a Nernstian slope of 19.7±0.2 mV per decade^-1 of Al³⁺ concentration. The electrode response is independent of pH in the range of 3.5-7.0 with short the response time of about 5 s. The potentiometric selectivity coefficients of proposed Al³⁺ ion selective electrode calculated based on fixed interference method, separation solution method, and matched potential method show its moderate selectivity for Al³⁺ ion toward other metal ions. Finally, the proposed electrode is successfully used as an indicator for potentiometric determination of Al³⁺ in water samples.