Development of an automatic continuous analyzer for water-soluble gases in air by combining an artificial lung with an ion chromatograph

An automatic measurement system for the simultaneous monitoring of sulfur dioxide (SO2) and ammonia (NH3) in air was developed by combining an artificial lung and an ion chromatograph. An artificial lung was used as a new technique for concentrated collection of trace amounts of gaseous pollutants in air. It was found that SO2 and NH3 were effectively absorbed into ultra-pure water in the artificial lung. Collection efficiencies for SO2 and NH3 were 100% and 98%, respectively, at a gas flow rate of 1 l min–1, and material balances >90% were obtained. No interference from the simultaneous collection of SO2 and NH3 was found. When a 400 ppb standard NH3 gas was measured automatically with this system, the recovery rate was 98%, and the relative standard deviation was 2.7% (n=8). In the case of a 200 ppb standard SO2 gas, the recovery rate was 87%, and the relative standard deviation was 1.6% (n=7). Results from the simultaneous measurement of SO2 and NH3 with the automatic system were equally as good as those obtained by measuring a single component at a time. Calibration curves for SO2 and NH3 showed good relationships between concentration and peak intensity. The linear correlation coefficients were 0.997 and 0.998 for SO2 and NH3, respectively. The detection limits of SO2 and NH3 were 0.06 and 0.1 ppb, respectively, in a 40 l air volume. The system was tested in air and found to be capable of simultaneous measurement of SO2 and NH3 with a 20 min cycle.