The automated calibration and analysis of very low mixing ratios of the reactive volatile organic halocarbons CH3I, CHCl3, C 2H5I, 2-C3H7I, CH2Br 2, CH2ClI, CHBr2Cl, 1-C3H 7I, CH2BrI, CHBr3 and CH2I 2 for long term atmospheric field measurements are described. Analytes were pre-concentrated from 3 1 of air onto an adsorbent trap cooled to -10°C using Peltier plates, and rapidly transferred to a gas chromatograph (GC) by resistive heating. A two stage Carboxen 1016/Carbotrap C adsorbent trap allowed good analyte recovery and rapid desorption without the need for post-desorption cryofocussing. Halocarbons were detected using a mass spectrometer (MS) in selective ion mode. Detection limits were between 0.02 and 0.12 pptv (parts per trillion by volume) for approximately hourly samples of CHCl3, CH3I, C2H5I, 1-C 3H7I, 2-C3H7I, CH2ClI, CH2Br2, CHBr2Cl, CH2BrI, CHBr 3 and CH2I2 with a precision of 3-8%. A novel calibration system was constructed which utilised fixed volume (50 μl) injections of the output of thermostatted permeation tubes into a stream of nitrogen gas in order to dilute parts per million by volume (ppmv) mixing ratios into pptv. The calibration was completely automated, allowing multi-point calibrations during routine operation. The overall accuracy of the measurements is estimated to be ±15%. The instrument was used continuously for automated atmospheric measurements during a 4-month research cruise from Germany to Antarctica, and a 6 week field campaign at Mace Head, Ireland. The results for CHCl3 during the latter campaign were within 13% of measurements made by a GC-MS operating continuously at the site within the long term Advanced Global Atmospherics Gases Experiment.
CITATION STYLE
Wevill, D. J., & Carpenter, L. J. (2004). Automated measurement and calibration of reactive volatile halogenated organic compounds in the atmosphere. Analyst, 129(7), 634–638. https://doi.org/10.1039/b403550j
Mendeley helps you to discover research relevant for your work.