Development of an optical flow-through biosensor for the determination of sulphite in environmental samples

A continuous-flow biosensor arrangement based on the dual immobilization of a biocatalyst on controlled-pore glass and the reaction product on a resin support both packed in the flow-cell of a photometric detector for the determination of sulphite is proposed. The method thus developed affords low detection and quantitation limits (3 and 10 ng ml−1 of sulphite, calculated as ±3σ and ±10σ, respectively, for n = 20), wide linear range (10–1000 ng ml−1 of sulphite), good precision (R.S.D. = 2.6% for 60 ng ml−1 and 0.7% for 200 ng ml−1 of the analyte), and a sampling frequency of 16 h−1. The hydrodynamic assembly has been applied to the determination and recovery of the analyte in spiked, aqueous samples with excellent results.