Nitrite reduction and detection at a carbon paste electrode containing hemoglobin and colloidal gold

Area of Science:

• Electrochemistry
• Biosensors
• Nanotechnology

Background:

• Nitrite (NO2-) is an important analyte in environmental and biological systems.
• Development of sensitive and selective biosensors for nitrite detection is crucial.
• Existing methods may lack sensitivity, selectivity, or require reagent use.

Purpose of the Study:

• To develop a novel, renewable, and reagentless nitrite biosensor.
• To investigate the direct electron transfer of immobilized hemoglobin (Hb) for nitrite sensing.
• To establish a new sensing mechanism for sensitive nitrite determination.

Main Methods:

• Fabrication of a biosensor using colloidal gold nanoparticle and carbon paste technology with immobilized Hb.
• Electrochemical characterization of the immobilized Hb.
• Amperometric detection of nitrite based on an interfacial charge transfer followed by a chemical reaction (EC) mechanism.

Main Results:

• The immobilized Hb exhibited direct electrochemistry with a formal potential of -42 mV (vs. NHE).
• The biosensor showed sensitive determination of nitrite with a linear range of 0.1–9.7 µmol dm⁻³ and a detection limit of 0.06 µmol dm⁻³.
• A linear range of 0.1–1.2 mmol dm⁻³ was achieved for high nitrite concentrations at pH 4.0.
• The biosensor surface was renewable and demonstrated satisfactory performance in native water samples.

Conclusions:

• A novel and efficient reagentless nitrite biosensor was successfully developed.
• The biosensor, based on Hb direct electron transfer and an EC mechanism, offers high sensitivity and renewability.
• The developed biosensor is suitable for practical nitrite determination in real water samples.