lunes, 8 de octubre de 2018

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

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 hours), 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-hour average ambient air ozone levels in the range 20
– 120
mg/m3 (detection limit 1.6 mg/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 13752. 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. Read more.