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

Hydrogen peroxide (H2O2) 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 H2O2, a tubular reactor containing immobilized peroxidase was constructed using an immobilization of enzymes on Amberlite IRA-743 resin. The linear dynamic range in H2O2 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.