Denuder tube preconcentration and detection of gaseous ammonia using a coated quartz piezoelectric crystal

The feasibility of using a cylindrical denuder tube for sampling gaseous ammonia, followed by detection with a piezoelectric quartz crystal, was investigated. Gaseous ammonia was sampled with a tungsten oxide-coated cylindrical denuder tube and then thermally desorbed onto a piezoelectric quartz crystal coated with pyridoxine hydrochloride–Antarox CO-880. A linear calibration graph of peak area response versus ammonia concentration sampled was obtained for ammonia concentrations between 3.1 and 8.2 µg l–1. A concentration of 29 ng l–1 of ammonia in air was detected with a signal-to-background ratio of 14:1 by achieving an enrichment ratio of 900 with the tungsten oxide denuder tube.