Multivariate diagnostics of electrochemical sensor drift by in situ impedance spectroscopy and voltammetry: A benzenediol-based framework

Performance drift in electrochemical sensors remains a challenge in long-term and/or corrosive applications. We present a generalisable , in situ diagnostic framework based on electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), using screen-printed electrodes (SPE) and benzenediols (catechol, resorcinol and hydroquinone) in acidic media as a model system. Two sensor types, unmodified and Pt/C-modified SPEs, were tested across repeated CV cycles, with polarisation resistance ( R P ) and effective capacitance ( C eff ) extracted from equivalent circuit models. Unmodified SPEs showed progressive activation, while modified SPEs exhibited early improvement followed by degradation. To synthesise trends across R P , C eff , and net charge transfer ( Qₙ ) obtained from CV data, principal component analysis (PCA) was applied. PCA revealed smooth, directional evolution for unmodified SPEs and disordered, non-monotonic drift in modified SPEs, reinforcing the EIS results. This approach enables online, non-destructive tracking of electrochemical sensor health and offers a transferable framework for performance assurance, quality control, and lifecycle monitoring. It repositions EIS from static characterisation to an embedded, multivariate diagnostic tool. • Electrochemical Impedance Spectroscopy with Cyclic Voltammetry tracks sensor drift. • Principal Component Analysis of resistance, capacitance, and charge transfer reveals performance trends. • Benzenediol sensing validates the diagnostic framework.