AUTOMATED DETERMINATION OF HYDROGEN PEROXIDE AT THE MICRO-MOLAR LEVEL IN RAINWATER AND SNOW USING A STOPPED-FLOW APPROACH IN A HYBRID SEQUENTIAL INJECTION/FLOW INJECTION MANIFOLD

A new automated method is reported for the determination of H2O2 in real samples. The method is based on the quenching effect of the analyte on the reaction between tris(2-carboxyethyl) phosphine (TCEP) and Ellman's reagent (DTNB). All necessary steps were accomplished under flow conditions using a hybrid sequential injection (SI)/flow injection (FI) setup. The sensitivity was enhanced by applying a stopped-flow step (120s) in order to promote the reaction between H2O2 and TCEP. The proposed analytical protocol was validated for linearity (10-75 mu mol L-1), limits of detection (c(L) = 1.0 mu mol L-1), quantitation (c(Q) = 3.3 mu mol L-1), precision (s(r) = 1.3-1.7%), accuracy, and selectivity. It was then applied successfully to the analysis of H2O2 in spiked rainwater and snow samples.