Ultramicroelectrode array modified with magnetically labeled Bacillus subtilis, palladium nanoparticles and reduced carboxy graphene for amperometric determination of biochemical oxygen demand

Abstract

The authors describe a microsensor for the determination of biochemical oxygen demand. Different from established BOD detection schemes that incorporate a film of immobilized microbes, the sensitive element of this BOD microsensor consists of magnetite-functionalized Bacillus subtilis that can be immobilized and regenerated on an ultramicroelectrode array (UMEA). Modification and regeneration are magnetically controlled. The oxygen consumed is amperometrically quantified by using an UMEA modified with palladium nanoparticles and reduced carboxy graphene. The assay can be performed within 5 min owing to the fast mass transfer of the magnetite-functionalized microbes on the surface of the UMEA. The calibration plot, best acquired at a voltage of -0.4 V vs. Ag/AgCl, is linear in the 2 to 15 mg⋅L−1 BOD concentration range. A critical comparison with other BOD sensor shows the sensitivity of this sensor to be largely improved. It was successful applied to the determination of BOD in spiked water samples.