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Cavity ring-down spectroscopy with an automated control feedback system for investigating nitrate radical surface chemistry reactions.
Rev Sci Instrum 2012 Aug; 83(8):085103
Nitrate radical (NO3*) surface chemistry of indoor environments has not been well studied due to the difficulty in generating and maintaining NO3* at low concentrations for long term exposures. This article presents the Surface Chemistry Reactant Air Delivery and Experiment System (SCRADES), a novel feedback controlled system developed to deliver nitrate radicals at specified concentrations (50-500 ppt, +/-30 ppt) and flow rates (500-2000 ml min-1) to a variety of indoor surfaces to initiate reaction chemistry for periods of up to 72 h. The system uses a cavity ring-down spectrometer (CRDS), with a detection limit of 1.7 ppt, to measure the concentration of NO3* supplied to a 24 1 experiment chamber. Nitrate radicals are introduced via thermal decomposition of N2O5 and diluted with clean dry air until the desired concentration is achieved. Additionally, this article addresses details concerning NO3* loss through the system, consistency of the NO3* concentration delivered, and stability of the CRDS cavity over long exposure durations (72 h).
Indoor-environmental-quality; Nitrates; Organic-compounds; Aldehydes; Ketones; Carboxylic-acids; Dicarboxylic-acids; Air-contamination; Analytical-processes; Analytical-chemistry; Indoor-air-pollution
Jason E. Ham, Exposure Assessment Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, West Virginia 26505
Issue of Publication
Healthcare and Social Assistance; Services
Review of Scientific Instruments
Page last reviewed: September 2, 2020Content source: National Institute for Occupational Safety and Health Education and Information Division