Differential amperometric determination of hydrogen peroxide in honeys using flow-injection analysis with enzymatic reactor

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Hydrogen peroxide (H 2O 2) present in honey was rapidly determined by the differential amperometric method in association with flow-injection analysis (FIA) and a tubular reactor containing immobilized enzymes. A gold electrode modified by electrochemical deposition of platinum was employed as working electrode. Hydrogen peroxide was quantified in 14 samples of Brazilian commercial honeys using amperometric differential measurements at +0.60 V vs. Ag/AgCl (sat). For the enzymatic consumption of H 2O 2, a tubular reactor containing immobilized peroxidase was constructed using an immobilization of enzymes on Amberlite IRA-743 resin. The linear dynamic range in H 2O 2 extends from 1 to 100 × 10 −6 mol L −1, at pH 7.0. At flow rate of 2.0 mL min −1 and injecting 150 μL sample volumes, the sampling frequency of the 90 determinations per hour is afforded. This method is based on three steps involving the flow-injection of: (1) the sample spiked with a standard solution, (2) the pure sample and (3) the enzymatically treated sample with peroxidase immobilized. The reproducibility of the current peaks for hydrogen peroxide in 10 −5 mol L −1 range concentration showed a relative standard deviation (R.S.D.) better than 1%. The detection limit of this method is 2.9 × 10 −7 mol L −1. The honey samples analyses were compared with the parallel spectrophotometric determination, and showed an excellent correlation between the methods.