Magnetic silica/titania xerogel applied as electrochemical biosensor for catechol and catecholamines

A magnetic silica/titania material with planned textural properties was obtained by sol-gel method through hydrolysis and condensation of tetraethyl orthosilicate and titanium isopropoxide in the presence of magnetite particles. The resultant material (SiTiMPs) was used as support for direct immobilization of tyrosinase (SiTiMPs-Ty) avoiding additional modification steps. This was possible due to the chemical reactivity of titania due to its surface acidity and also to the textural properties of the material like pore size near 20 nm and specific surface area of 158 m2 g−1. These characteristics combined to the presence of magnetite lead to possibility to prepare carbon paste electrodes with SiTiMPs-Ty material with high electroactive area when tested in the ferricyanide/ferrocyanide redox system. This electrode was applied as efficient electrochemical biosensor for catechol and catecholamines, such as dopamine and epinephrine. It can be observed great sensitivities for all analytes tested in wide linear range. The calculated detection limits were 0.23 μmol L−1, 0.72 μmol L−1 and 2.94 μmol L−1 for catechol, dopamine and epinephrine, respectively. This electrode presented excellent response for simultaneous analyses of catechol and epinephrine, with high sensitivity and low detection limits. The present sensor showed good reproducibility for catechol detection with a relative standard deviation of 6.9% (n = 5).