A novel conductometric creatinine biosensor based on solid-state contact ammonium sensitive PVC–NH2 membrane

► This study reports a novel, highly sensitive and stable conductometric biosensor. ► The biosensor was based on solid-state contact ammonium-sensitive membrane sensor chip. ► Creatininase was chemically immobilized on the surface of the ammonium sensitive membrane. ► The biosensor exhibited reproducible and stable response at least for 10h. ► It also showed excellent operational and storage stability for at least 4 weeks. A novel, highly sensitive and stable conductometric biosensor for creatinine determination is developed. The biosensor is based on solid-state contact ammonium-sensitive sensor. Creatininase is chemically immobilized on the surface of the solid-state contact ammonium-sensitive membrane via glutaraldehyde covalent attachment method. The developed conductometric creatinine biosensors demonstrate high sensitivity and short response time toward creatinine. The detection limit of the biosensor was about 2×10−6M and the response time was shorter than 10s in phophate buffer solution at pH 7.20. The linear dynamic range of the biosensor was between 1×10−1 and 9×10−6M creatinine concentration in phosphate buffer solution at pH 7.20. The biosensor exhibited good operational and storage stability for at least 4 weeks kept in dry at 4–6°C. It had a reproducible and stable response during continuous work at least for 10h with the relative standard deviation of 0.5% (n=48) for creatinine of 1×10−3M in phosphate buffer solution.