Beyond potentiometry: an amperometric approach to urea detection using antimony electrodes

In this study, we present an amperometric urea biosensor based on a custom-made antimony electrode modified with an enzymatic membrane containing immobilised urease. The biosensor showed a high sensitivity, ranging from 306.6 to 77.5 nA/mM depending on the buffer solution capacity (5–50 mM PBS). Stability tests demonstrated that the sensor retained 65% of its initial activity after 10 days at room temperature. Good repeatability was observed, with relative standard deviations below 10% for 10 replicate measurements at 0.5 mM urea. Validation with aqueous samples showed a strong correlation with a commercial colorimetric assay, with deviations not exceeding 10%. During the tests with biological samples (human saliva and serum), the biosensor reported lower urea concentrations compared with the colorimetric method, indicating that interfering compounds present in complex biological matrices can affect biosensor performance. The developed biosensor represents a simple, cost-effective and adaptable platform for urea determination, showing a strong potential for integration into point-of-care diagnostic systems.