Urea solid-state biosensor suitable for continuous dialysis control

A solid state potentiometric biosensor for urea determination was assembled coupling a nonactin-based ISE without an internal solution with immobilized urease. The system proved to be useful for continuous monitoring of urea during dialysis treatment using the ultrafiltrate of blood as sample. A noticeable shift of potential occurred during the dialysis (probably due to continuous extraction of ionophore by the ultrafiltrate). Therefore a flow injection analysis assembly was necessary to control the shift of electrode potential.