A Nitrite Biosensor Based on Coimmobilization of Nitrite Reductase and Viologen‐Modified Polysiloxane on Glassy Carbon Electrode

Copper containing nitrite reductase (Cu‐NiR) and viologen‐modified sulfonated polyaminopropylsiloxane (PAPS‐SO 3 H‐V) were co‐immobilized on glassy carbon electrode (GCE) by hydrophilic polyurethane (HPU) drop‐coating, and the electrode was tested as a reagentless electrochemical biosensor for nitrite detection. The newly synthesized PAPS‐SO 3 H‐V as an electron transfer (ET) mediator between electrode and NiR was effective, and could be effectively immobilized in HPU membrane. The NiR and PAPS‐SO 3 H‐V co‐immobilized GCE used as a nitrite biosensor showed the following performance factors: sensitivity=12.0 nA μM −1 , limit of detection ( LOD )=60 nM ( S / N =3), linear response range=0–18 μM ( r 2 =0.996) and response time ( t 90% )=60 s, respectively. Lineweaver–Burk plot shows that apparent Michaelis–Menten constant ( K $\rm{{_{M}^{app}})}$ is 101 μM. Storage stability of the sensor is 51 days (80% of initial activity) in condition of storing in ambient air at room temperature. The sensor showed a relative standard deviation ( RSD ) of 3.2% ( n =5) even in condition of injection of 1 μM nitrite. Interference study showed that common anions in water sample such as chlorate, chloride, sulfate and sulfite do not interfere with the nitrite detection. However, nitrate interfered with a relative sensitivity of 80% due to inherent character of the enzyme used.