A pulse amperometric sensor for the measurement of atmospheric hydrogen peroxide

Gaseous H2O2 is sampled through a Nafion membrane diffusion scrubber while 1 mM HCl is maintained stationary in the scrubber. After a preselected preconcentration time (typically, 5-10 min), a valve is opened to allow the scrubber liquid to now by gravity over an electrochemical H2O2 sensor for a brief period. The miniature flow-over sensor consists of a Pt/Rh wire working electrode and a Pt wire counter electrode wound respectively on separate segments of a Nafion solid polymer electrolyte tubing supported on a Ag/AgCl wire reference electrode. A simple electronic interface and a personal computer are used to control and record the electrochemical measurement. The liquid phase detection limit for this sensor is similar to 30 nM H2O2 in the anodic oxidation mode. For a 9 min gas sample preconcentration period, the LOD (S/N = 3 criterion) is 0.11 ppbv H2O2(g). Ambient H2O2 data obtained with this instrument were in excellent agreement with those obtained by an established fluorometric technique in a blind intercomparison.