Electrochemical determination of l-vanillin using copper hexacyanoferrate film modified gold nanoparticle graphite-wax composite electrode

A simple and sensitive electrochemical determination of l-vanillin (VA), a powerful anti-microbial agent and a commonly employed food preservative was investigated using copper hexacyanoferrate (CuHCF) film modified on 2-mercaptoethylamine functionalized colloidal gold nanoparticles (colloid-Au) graphite-wax composite electrode. As achieved surface modification was characterized using confocal Raman spectroscopy studies which gave rise to peaks at 351, 493, 807 and 2048 cm⁻¹ that corresponds to the characteristics vibrational modes of ν(Fe–C ≡N–Cu), ν(Cu–N), ν(Fe–C) and ν(–C≡N) for the CuHCF film. Further, the elemental analysis investigated using X-ray photoelectron spectroscopy confirms the presence of 2p peaks of Cu (II), Fe(II) and 1 s edge peaks of N for the CuHCF film modified electrode. The modified electrode exhibited a high sensitivity of 0.1817 μA μM⁻¹ at a lower detection potential of 0.68 V towards the VA determination and the limit of detection was observed to be 2.53 × 10⁻⁷ M (S/N = 3). The VA content in commercial roasted coffee beans was also examined with the proposed sensor and the results were found to be satisfactory.