Automated Low-Pressure Carbonate Eluent Ion Chromatography System with Postsuppressor Carbon Dioxide Removal for the Analysis of Atmospheric Gases and Particles

• Published in: Aerosol science and technology 2005-11, Vol.39 (11), p.1072-1084
• Main Authors: Rahmat Ullah, S. M., Williams, Allen, Dasgupta, Purnendu K.
• Format: Article
• Language: English
• Subjects: Aerosols; Carbon dioxide; Chemistry; Chromatography; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry
• ISSN: 0278-6826; 1521-7388
• DOI: 10.1080/02786820500421554

We present a low-pressure, automated, semi-continuous Gas-Particle Ion Chromatograph to measure soluble ionogenic gases and soluble ionic constituents of PM 2.5 . The system utilizes a short separation column, an isocratic carbonate eluent and post suppressor CO 2 removal. Measured constituents include ammonium, nitrate, and sulfate in the particle fraction, and nitric acid, sulfur dioxide, and ammonia among soluble gases. Two independent sampling channels are used. In one channel, a wet denuder collects soluble gases. In the second channel, following removal of large particles by a cyclone and soluble gases by a wet denuder, a hydrophobic filter-based particle collector collects and extracts the soluble components of PM 2.5 . The aqueous particle extract is aspirated by a peristaltic pump onto serial cation and anion preconcentrator columns. Gas samples are similarly loaded onto another set of serial cation and anion preconcentrator columns. The cation preconcentrator is eluted with NaOH and the evolved NH 3 is passed across a membrane device whence it diffuses substantially into a deionized water receptor stream; the conductivity of the latter provides a measure of NH 3 (NH 4 + ). The anion preconcentrator column(s) are subjected to automated periodic analysis by ion chromatography. This system provides data every 30 min for both particles (NO 3 − , SO 4 2 − and NH 4 + ) and gases (HNO 3 , SO 2 and NH 3 ). Gas and particle extract samples are each collected for 15 min. The analyses of the gas and particle samples are staggered 15 min apart. The limit of detection (S/N = 3) for NO 3 − , SO 4 2− and NH 4 + are 2.6, 5.3, and 2.1 ng/m 3 , respectively.