Novel Hybrid Copper-Based Electrode for Non-Enzymatic Electrochemical Lactic Acid Sensing in Milk Samples

Abstract

A novel developed non-enzymatic electrochemical sensor was designed for the detection of lactic acid (LA) in perishable products, with a focus on monitoring milk spoilage. The sensor utilizes a hybrid copper-based electrode consisting of cuprous oxide (Cu2O), copper oxide (CuO), and copper hydroxide (Cu(OH)2), which collectively contribute to enhanced performance through their synergistic effects. Cyclic voltammetric studies revealed distinct oxidation peaks associated with LA detection, highlighting the superior catalytic effect of the Cu2O/CuO/Cu(OH)2 electrode compared to CuO alone. Further optimization of the metal loading on the electrode surface led to improve LA sensing properties. The sensor exhibited a wide linear response range (0.25–7 mM), high sensitivity (817.66 μA·mM−1·cm−2), and a low limit of detection (0.25 mM). Selectivity tests indicated negligible interference from common dairy product constituents, while stability tests showed consistent performance over a 3 week storage period (100% stability). The practical usability of the sensor was demonstrated through the quantitative analysis of LA in pasteurized milk, with recovery values ranging from 99.7% to 106.9%, confirming the feasibility of the sensor for real sample analysis. The developed multiphase copper-based electrode presents a promising platform for the sensitive and reliable detection of LA within the dairy industry.