Error-calibrated sensing: ratiometric biosensor for carcinogenic formaldehyde in food safety monitoring.

Global food safety requires reliable biosensors in complex matrices. Yet, conventional single-signal electrochemical biosensors suffer from high inter-electrode variability (RSD <12.14%) and low accuracy (<87.84%) due to common-mode signal fluctuations. This study presents a ratiometric biosensor with a dual-electrode design that enables calculation of the current ratio (IWE2/IWE1) between a formaldehyde dehydrogenase-functionalized sensing electrode and an inert graphene reference to mitigate systemic fluctuations. This self-calibrating configuration reduced variability (RSD of 6.92%), improved accuracy (>97.29%), and minimized interference effects (from 7.54% to 1.52%). Spanning a linear range of 0.02-0.50 mM with a LOD of 0.004 mM, the biosensor achieved 97.22-103.87% recovery in coffee samples (RSD = 0.21%). Validation against the Nash assay showed strong correlation (R2 = 0.995) with comparable accuracy at 0.10-0.50 mM concentrations, yet up to nine-fold higher accuracy at 0.02 mM (p < 0.05), confirming its superior suitability for practical application in food safety monitoring.