| Title: | Cavity ring-down spectroscopy with an automated control feedback system for investigating nitrate radical surface chemistry reactions |
| Address: | "Exposure Assessment Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, West Virginia 26505, USA" |
| ISSN/ISBN: | 1089-7623 (Electronic) 0034-6748 (Print) 0034-6748 (Linking) |
| Abstract: | "Nitrate radical (NO(3)(?╖+)) surface chemistry of indoor environments has not been well studied due to the difficulty in generating and maintaining NO(3)(?╖+) 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 NO(3)(?╖+) supplied to a 24 l experiment chamber. Nitrate radicals are introduced via thermal decomposition of N(2)O(5) and diluted with clean dry air until the desired concentration is achieved. Additionally, this article addresses details concerning NO(3)(?╖+) loss through the system, consistency of the NO(3)(?╖+) concentration delivered, and stability of the CRDS cavity over long exposure durations (72 h)" |
| Keywords: | Automation *Feedback Free Radicals/chemistry Humidity Nitrates/*chemistry Nitrogen Oxides/chemistry Polytetrafluoroethylene/chemistry Spectrum Analysis/*instrumentation Volatile Organic Compounds/chemistry; |
| Notes: | "MedlineFlemmer, Michael M Ham, Jason E eng CC999999/Intramural CDC HHS/ 2012/09/04 Rev Sci Instrum. 2012 Aug; 83(8):085103. doi: 10.1063/1.4739768" |
