Portable analyzer for continuous monitoring of sulfur dioxide in gas stream based on amperometric detection and stabilized gravity-driven flow

摘要

The construction, optimization and application are described for a portable gas analyzer which gives real-time measurement of sulfur dioxide in a gas stream. The SO_2 is absorbed from the analyte gas stream into a gravity-driven carrier solution flowing through a diffusion scrubber (DS), in the form of a bundle of polymeric hollow fibers. The sulfite ions in the carrier solution are detected by anodic amper-ometry at a novel carbon nanotube (CNT) electrode polarized at 0.35 V vs Ag/AgCl reference electrode. A novel compact design is the result of integrating the DS with the amperometric detector and yields a light weight portable analyzer (900 g) with a small footprint. The optimized analyzer has favorable performance characteristics such as (ⅰ) good sensitivity (LOD=4ppm, S/N=3), (ⅱ) wide linear dynamic range up to 5000 ppm, (ⅲ) reasonably fast response time (t_(95%), 4.1 min), (ⅳ) excellent signal stability and repeatability (RSD = 1.3%), and (ⅴ) continuous standalone operation for 6 h. The interfering effect of H_2 S is avoided by removing H_2S using a prior guard column. The analyzer can successfully monitor the removal of SO_2 from SO_2-N_2 gas mixtures and in determining sulfite in foodstuffs.