Electrochemical determination of ethanol on carbon paste electrode chemically modified with [N,N '-cis-1,2-cyclohexylene bis (salicylideneaminate)] nickel(II) Schiff base complex

Author(s)

Lima, Guilherme Vieira ; Mello, Lucas dos Santos ; Dockal, Edward Ralph ; de Oliveira, Marcelo Firmino

• Document type: Journal article
• Source: Microchemical Journal; v. 175, p. 10-pg., 2022-01-21.

Abstract

This study describes two electroanalytical methods that employ a carbon paste electrode (CPE) chemically modified with [N,N'-cis-1,2-cyclohexylene-bis(salcylidenoaminate) nickel(II)] for ethanol oxidation-cyclic voltammetry (CV) and amperometry (AMP), both conducted in aqueous medium containing 1.0 mol L-1 NaOH as supporting electrolyte. For CV, potentials were scanned from 0.0 to + 0.8 V (vs Ag/AgCl) at 50 mV s(-1); for AMP, the applied potential for ethanol oxidation was + 0.55 V (vs Ag/AgCl). During CPE modification, the CPE was heated with the [Ni(cis-salcn)] complex at 60 degrees C, to ensure paste agglutination. The [Ni(cis-salcn)] thermal stability was assessed by thermogravimetric analyses and differential scanning calorimetry, which demonstrated that the complex was stable up to 350 degrees C. Scanning electron microscopy and energy dispersive spectrometry revealed uniform [Ni(cis-salcn)] distribution on the chemically modified electrode surface. The proposed mechanism for electron exchange between ethanol and the electrode surface involved ethanol oxidation by the complex [(cis-salcn)(H2O)Ni(III)ONi(III)(OH)(cis-salcn)](-) (Ni III), generated by electrochemical [Ni(cis-salcn)] activation in alkaline medium (1 mol L-1 NaOH). Ethanol was quantified by single-pulse amperometry, which showed linear dependence from 5 to 250 mmol L-1 with linear determination coefficient of 0.9918 +/- 0.0058, average amperometric sensitivity of 1.33 mu A L mmol(-1), limit of detection of 0.75 mmol L-1, and limit of quantification of 2.50 mmol L-1. Therefore, compared to other nickel compounds reported in the literature, [Ni(cis-salcn)] displays good amperometric sensitivity, which is important for the development of techniques for electrochemical ethanol oxidation for diverse purposes. (AU)

• FAPESP's process: 16/23825-3 - Development of voltammetric sensors for determination of cocaine and delta-9-tetrahydrocannabinol in samples seized by the police
• Grantee: Marcelo Firmino de Oliveira
• Support Opportunities: Regular Research Grants