Fast batch injection analysis of H2O2 using an array of Pt-modified gold microelectrodes obtained from split electronic chips

Graphical abstract: Highlights: → An array of gold microelectrodes modified with Pt was used for batch injection analysis of H2O2 in rainwater. → The microelectrode array (n = 14) was obtained from electronic chips developed for surface mounted device technology. → The analytical frequency of the method can attain 300 determinations per hour. → The volume-weighted mean concentration of H2O2 in rainwater investigated (n = 25) was 14.2 μmol L-1. - Abstract: A fast and robust analytical method for amperometric determination of hydrogen peroxide (H2O2) based on batch injection analysis (BIA) on an array of gold microelectrodes modified with platinum is proposed. The gold microelectrode array (n = 14) was obtained from electronic chips developed for surface mounted device technology (SMD), whose size offers advantages to adapt them in batch cells. The effect of the dispensing rate, volume injected, distance between the platinum microelectrodes and the pipette tip, as well as the volume of solution in the cell on the analytical response were evaluated. The method allows the H2O2 amperometric determination in the concentration range from 0.8 μmol L-1 to 100 μmol L-1. The analytical frequency can attain 300 determinations per hour and the detection limit was estimated in 0.34 μmol L-1 (3σ). The anodic current peaks obtained after a series of 23 successive injections of 50 μL of 25 μmol L-1 H2O2 showed an RSD < 0.9%. To ensure the good selectivity to detect H2O2, its determination was performed in a differential mode, with selective destruction of the H2O2 with catalase in 10 mmol L-1 phosphate buffer solution. Practical application of the analytical procedure involved H2O2 determination in rainwater of Sao Paulo City. A comparison of the results obtained by the proposed amperometric method with another one which combines flow injection analysis (FIA) with spectrophotometric detection showed good agreement.