Flow-injection system with enzyme reactor for differential amperometric determination of hydrogen peroxide in rainwater

Differential determinations of hydrogen peroxide (H2O2) have been performed by amperometry, combining flow-injection analysis (FIA) and a tubular reactor containing immobilized enzymes. A gold microelectrode modified by electrochemical deposition of platinum was employed as working electrode. Hydrogen peroxide was quantified in rainwater using amperometric differential measurements at +0.60 V versus Ag/AgCl(sat). For the enzymatic consumption Of H2O2, a tubular reactor containing immobilized catalase was constructed, using a novel way for immobilization of enzymes on Amberlite IRA-743 resin. The linear dynamic range in H2O2 extends from 1 to 100 x 10(-6) mol/l, at pH 7.0. At flow rate of 2.0 ml/min and injecting 150 mul sample volumes, the sampling frequency of the 90 determinations/h is afforded. The reproducibility of the current peaks for hydrogen peroxide in 10(-5) mol/l range concentration shown a R.S.D. better than 1%. The detection limit of the method is 2.9 x 10(-7) mol/l (1.5 ng of H2O2 in a 150 pd sample). The rainwater samples analyses were compared with the parallel amperometric determinations using static mercury electrode and by spectrophotometry, showing very good correlation between the three methods. (C) 2001 Elsevier Science B.V. All rights reserved.