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 reac tor containing immobilized enzymes. A gold microelectrode modified by elect rochemical deposition of platinum was employed as working electrode. Hydrog en peroxide was quantified in rainwater using amperometric differential mea surements at +0.60 V versus Ag/AgCl(sat). For the enzymatic consumption Of H2O2, a tubular reactor containing immobilized catalase was constructed, us ing a novel way for immobilization of enzymes on Amberlite IRA-743 resin. T he 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 reproducibil ity of the current peaks for hydrogen peroxide in 10(-5) mol/l range concen tration 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 samp les analyses were compared with the parallel amperometric determinations us ing static mercury electrode and by spectrophotometry, showing very good co rrelation between the three methods. (C) 2001 Elsevier Science B.V. All rig hts reserved.