Fabrication and electrochemical behavior of hemoglobin modified carbon ionic liquid electrode

A new hemoglobin (Hb) and room temperature ionic liquid modified carbon paste electrode was constructed by mixing Hb with 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) and graphite powder together. The Hb modified carbon ionic liquid electrode (Hb-CILE) was further characterized by FT-IR spectra, scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Hb in the carbon ionic liquid electrode remained its natural structure and showed good direct electrochemical behaviors. A pair of well-defined quasireversible redox peaks appeared with the apparent standard potential (E') as -0.334 (vs. SCE) in pH 7.0 phosphate buffer solution (PBS). The electrochemical parameters such as the electron transfer number (n), the electron transfer coefficient (alpha) and the heterogeneous electron transfer kinetic constant (k(s)) of the electrode reaction were calculated with the results as 1.2, 0.465 and 0.434 s(-1), respectively. The fabricated Hb-CILE exhibited excellent electrocatalytic activity to the reduction of H2O2. The calibration range for H2O2 quantitation was between 8.0 x 10(-6) mol/L and 2.8 x 10(-4) mol/L with the linear regression equation as I-ss (mu A) = 0.12 C (mu mol/L) + 0.73 (n = 18, gamma = 0.997) and the detection limit as 1.0 x 10(-6) mol/L (3 sigma). The apparent Michaelis-Menten constant (K-M(app)) of Hb in the modified electrode was estimated to be 1.103 mmol/L. The surface of this electrochemical sensor can be renewed by a simple polishing step and showed good reproducibility.