ABSTRACT This paper presents a new Schiff base molecule of (Z)-N’-(2-hydroxy-5-nitrobenzylidene) nicotinohydrazide (BNH) that has been synthesised and characterised using Fourier transform infrared spectroscopy, Proton and Carbon-13 Nuclear Magnetic Resonance and High-resolution Ionisation Mass Spectroscopy. The study herein describes the novel chemical modification of glassy carbon electrode (GCE) by drop casting method using the synthesised Schiff base molecule to detect tetracycline (TC) antibiotic. Improved sensitivity of the electrode to the analyte results from the electrode modification using functional group present in the Schiff bases. The electrochemical behaviour of a modified electrode on tetracycline using voltammetric techniques were studied and optimised. The modified electrode showed a good selectivity in the presence of some interferences. The calibration curve for TC was achieved in a linear range of 10–60 μmol L−1 under optimised conditions. The detection limit and quantification for TC was found to be 2.1 μmol L−1 and 9 μmol L−1. The obtained results suggested that tetracycline may be measured in milk samples using the BNH modified glassy carbon electrode.