A hydroquinone biosensor using modified core–shell magnetic nanoparticles supported on carbon paste electrode

Abstract A hydroquinone biosensor was developed and used to determine hydroquinone concentration in compost extracts based on the immobilization of laccase on the surface of modified magnetic core–shell (Fe 3 O 4 –SiO 2 ) nanoparticles. Laccase was covalently immobilized on the magnetic nanoparticles by glutaraldehyde, which was modified with amino groups on its surface. The obtained magnetic bio-nanoparticles were attached to the surface of carbon paste electrode with the aid of a permanent magnet to determine hydroquinone. A good microenvironment for retaining the bioactivity of laccase was provided by the immobilization matrix. The linear range for hydroquinone determination was 1 × 10 −7 to 1.375 × 10 −4  M, with a detection limit of 1.5 × 10 −8  M. The current reached 95% of the steady-state current within about 60 s. Hydroquinone concentration in compost extracts was determined by laccase biosensor and HPLC, the results of the two methods were approximately the same.