Amperometric monitoring of hydrogen peroxide in workplace atmospheres by electrodes supported on ion-exchange membranes

An amperometric sensor is described which is suitable for the continuous mo nitoring of traces of hydrogen peroxide present in workplace atmospheres as gaseous species or as aerosols, without preliminary concentration steps be ing needed. It consists of a porous Pt sensing electrode, facing the sample , chemically deposited onto one side of a Nafion(R) 117 membrane which acts as a solid polymer electrolyte (SPE). The uncoated side of this membrane i s contacted by an electrolyte solution (0.2 M acetate buffer at pH 4.8, +0. 8 M NaClO4) contained in an internal compartment equipped with a Pt counter electrode and a Ag \ AgCl \ Cl-(sat.)(-) reference electrode. Hydrogen per oxide detection was achieved by applying a potential of 1.0 V to the sensin g electrode, which was chosen on the basis of preliminary voltammetric inve stigations. The anodic current due to the oxidation of hydrogen peroxide in creases linearly with its concentration within a wide range (from 0.1 to 40 ppm v/v) and a detection limit of 40 ppb v/v was estimated for a signal-to -noise ratio of 3. The estimated detection limit is about three orders of m agnitude lower than I ppm. which is the recommended exposure limit for hydr ogen peroxide in workplace atmospheres, evaluated as an 8-h time-weighed av erage concentration. Moreover, the long term stability of this amperometric sensor appears to be totally satisfactory in that reproducible responses w ere observed even after long periods of continuous use. The absence of sign ificant interfering effects is also discussed. (C) 2001 Elsevier Science B. V. All rights reserved.