Direct electrochemistry and electrocatalysis of myoglobin immobilized on Fe2O3 nanoparticle-sodium alginate-ionic liquid composite-modified electrode.

A biocomposite material composed of sodium alginate (SA), Fe(2)O(3) nanoparticles, and ionic liquid 1-decyl-3-methylimidazolium bromide ([DMIM]Br) was fabricated and used for the immobilization of myoglobin (Mb) on the surface of a carbon ionic liquid electrode (CILE). The CILE was fabricated by mixing graphite powder with ionic liquid N-butylpyridinium hexafluorophosphate (BPPF(6)) together. UV-Vis absorption and FTIR spectroscopic results indicated that Mb retained its native structure in the composite material. A pair of well-defined redox peaks appeared on the cyclic voltammogram in pH 7.0 phosphate buffer solution (PBS) with the formal peak potential (E(0')) at -0.256 V (versus SCE), which was the typical electrochemical behavior of Mb heme Fe(III)/Fe(II) redox couples. The Mb-modified electrode showed good electrocatalytic activity to the reduction of trichloroacetic acid (TCA) and NaNO(2) with wide linear range, good sensitivity, and reproducibility. The calibration range for TCA detection was between 0.6 and 12.0 mmol L(-1) with the linear regression equation as Iss (μA)=42.44C (mmol L(-1))+50.57 and a detection limit of 0.4 mmol L(-1) (3σ). The Mb-modified electrode also applied to NaNO(2) determination in the concentration range from 4.0 to 100.0 mmol L(-1) with a detection limit of 1.3 mmol L(-1) (3σ). So the proposed electrode has potential applications as third-generation biosensors.