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
Healthcare and Social Assistance; Services
Review of Scientific Instruments