Salicylaldehyde based Schiff base: synthesis, characterisation and application for selective electrochemical detection of Cu²⁺ in real samples

ABSTRACT

A simple salicylaldehyde-based Schiff base 2,2'-((1,3-phenylenebis(azanylylidine))bis(methanylylidene))dipehnol (PAMD) was synthesised by condensation reaction between salicylaldehyde and benzene-1,3-diamine (2:1 ratio) and characterised by spectral techniques such as NMR, FTIR and HRMS, followed by investigation for its spectroscopic behaviour towards diverse metal ions using UV and fluorescence studies. PAMD was found to exhibit sensitivity towards Cu²⁺ only. The receptor PAMD was then explored for its electrochemical behaviour using cyclic voltammetry, which displayed an irreversible anodic peak at 1.00 V due to imine group. Furthermore, PAMD was subjected to differential pulse voltammetry, which exhibited a sensitive response for Cu²⁺ in the linear range of 0–3.8 μM with lowest detection limit of 0.03 μM. The complexation between PAMD and Cu²⁺ was also supported by large values of binding constant (1.3 × 10⁵ M⁻¹) and negative free energy change (ΔG^∘ = -29.2 kJmol⁻¹) obtained from Benesi–Hildebrand equation. The carbon paste electrode (CPE) modified with PAMD displayed a Nernstian response to Cu²⁺ in the concentration range from 1.0 × 10⁻⁶ to 1.0 × 10⁻¹ M and lowest detection limit of 4.0 × 10⁻⁷ M. The PAMD-CPE was successfully applied for determination of Cu²⁺ content in real samples such as groundwater, soil, and food grains (wheat and rice).

KEYWORDS:

• Schiff base
• Cu²⁺ detection
• voltametric sensor
• carbon paste electrode
• water
• soil
• food grains

Acknowledgments

The authors acknowledge the financial support from Science & Engineering Research Board, Department of Science and Technology, New Delhi, and the Ministry of Human Resources Development, Government of India, under RUSA 2.0 Program. Both first author (S.K.) and second author (J.K.) are thankful to CSIR, New Delhi, for the senior research fellowship.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/03067319.2023.2247334.

Additional information

Funding

This work was supported by the Science and Engineering Research Board [SB/FT/CS-057/2014].