A label-free impedimetric strategy using interdigitated electrodes for tetracycline detection in Milk

The extensive use of tetracycline in livestock production has resulted in residues in dairy products, necessitating analytical methods that are accurate, robust, and compatible with complex food matrices. This work presents a label-free, non-enzymatic impedimetric sensor based on interdigitated electrodes (IDEs) for quantitative tetracycline detection in milk. Electrochemical impedance spectroscopy is used to monitor interfacial charge-transfer processes, emphasizing practical analytical translation rather than the development of new nanomaterials. The IDE-based sensor exhibits a signal-on response, with charge-transfer resistance decreasing monotonically as tetracycline concentration increases. Using Nernst-type linearization, the sensor achieves a linear range of 62.5-1000 nM, with limits of detection and quantification of 2.47 nM and 8.23 nM, respectively. High accuracy in spiked milk samples (relative error < 5%), strong matrix tolerance, good analytical discrimination, reproducibility, and stability demonstrate the sensor's practical potential for routine tetracycline residue screening in dairy products.