Water insoluble, self-binding viologen functionalized ionic liquid for simultaneous electrochemical detection of nitrophenol isomers

Herein, a water insoluble viologen functionalized ionic liquid (Vio-IL) was designed for the simultaneous electrochemical detection of 2-nitrophenol and 4-nitrophenol. Carboxyl functionalized benzimidazolium based ILs were hierarchically synthesized and the water insoluble carboxylic IL was covalently attached with aminopropylmethyl viologen through DCC coupling to obtain water insoluble Vio-IL gel. Vio-IL was immobilized by simple dropcasting over a multiwalled carbon nanotube deposited screen printed carbon electrode to obtain Vio-IL/MWCNT/SPE. The Vio-IL/MWCNT/SPE exhibited two sets of well-resolved redox peaks corresponding to V2+ to V+circle and V+circle to V-0 redox couple. Furthermore, Vio-IL/MWCNT/SPE has shown excellent electrocatalytic activity towards the reduction of 2- and 4-nitrophenol individually, and also for the simultaneous determination of 2- and 4-nitrophenol. The linear range, sensitivity and detection limit for simultaneous detection of 2-nitrophenol at Vio-IL/MWCNT/SPE were found to be 4-494 mu M, 0.884 mu A mu M-1 cm(-2), 1.5 mu M and that for 4-nitrophenol were 2-259 mu M, 2.615 mu A mu M-1 cm(-2), 0.70 mu M. The Vio-IL/MWCNT/SPE established excellent sensitivity and selectivity towards the simultaneous determination of 2- and 4-nitrophenol together with impressive stability and reproducibility. The exemplary analytical parameters achieved are due to the rational immobilization of the mediator covalently in the highly conducting IL/MWCNT backbone which maintained the mediator characteristics effectively. (C) 2020 Elsevier B.V. All rights reserved.