A passive sampling – voltammetric detection approach based on screen-printed electrodes modified with indigotrisulfonate for the determination of ozone in ambient air

Abstract

We explore in this work a novel analytical concept consisting on the combined use of chemically modified commercial screen-printed electrodes as passive samplers and voltammetric detectors for monitoring of ozone levels in ambient air, a highly relevant pollutant for air quality assessment. The proposed approach is based on the modification of commercial carbon screen-printed electrodes by surface deposition of a known amount of indigotrisulfonate (ITS). The screen-printed platforms are then inserted in passive sampler diffusive bodies and exposed to ambient air for a relatively short period (5 h), allowing the reaction of ITS with tropospheric ozone to proceed. After the sampling stage, the remaining ITS onto the electrode surface is solubilized in 0.1 M perchloric acid and quantified by square wave voltammetry using a portable potentiostat. The optimization of the experimental conditions allows to measure 5-h average ambient air ozone levels in the range 20–120 μg/m3 (detection limit 1.6 μg/m3), covering the usual ozone range in most urban and rural environments. The relative standard deviation of the combined passive sampling – voltammetric detection system varied from 9.5 to 17.6%. The proposed methodology was tested in field conditions against a reference UV absorption equipment with acceptable results showing a significant correlation at the 95% confidence level, with slope and intercepts not statistically different from expected values. The uncertainty of the proposed method was estimated to be in the range 25.6–26.2 according to ISO 13,752. The combination of cheap and simple sampling and detection based on chemically modified screen-printed electrodes opens new analytical options in ambient air monitoring, with promising applicability for decentralized testing by simple and affordable air pollution sensors.