Multi-walled carbon nanotube-functional ionophore based composite potentiometric sensor for selective detection of lead in water

Abstract

A functional ionophore (tetramethyl thiuram disulfide or TMTDS) and multi-walled carbon nanotubes (MWCNTs)-based composite paste was prepared by a novel and simple approach, to fabricate a two-electrode system for detection of lead ions in drinking water, by potentiometric method. Homogenous and properly dispersed paste was obtained by blending TMTDS and MWCNTs powder in silicon oil. The working electrode contained the ionophore and the potential between working and reference electrodes were used for assessing performance of the proposed sensor. Effect of various operating conditions, such as, concentration of TMTDS in working electrode, solution pH, temperature, inter-electrode distance and sensing time was carried out to obtain the best sensor. Highest sensitivity was achieved at 24 wt% TMTDS concentration, neutral pH, room temperature (298 K), 2-minute sensing time and 0.5 cm inter-electrode spacing. Following this, the best sensor was used for electrochemical characterization, such as, impedance spectroscopy, cyclic voltammetry, chronoamperometry and differential pulse voltammetry at different lead concentrations. Studies were also performed to show the content of different ions in the leachate solution from the prepared electrode. Compared to other conventional electrodes, synthesized composite paste-based electrode displayed significant enhancement in selective determination of lead. Proposed method offers scope for on-site detection of lead ions, even at trace levels, ranging from 0.2 μg/l till 150 μg/l. Sensitivity of the sensor toward lead ions was calculated and a detection limit of 31 μg/l was observed.