Development and validation of a portable gas phase standard generation and calibration system for volatile organic compounds

Abstract

Abstract. We report on the development of an accurate, portable, dynamic calibration system for volatile organic compounds (VOCs). The Mobile Organic Carbon Calibration System (MOCCS) combines the production of gas-phase VOC standards using permeation or diffusion sources with quantitative total organic carbon (TOC) conversion on a palladium surface to CO 2 in the presence of oxygen, and the subsequent CO 2 measurement. MOCCS was validated using three different comparisons: (1) TOC of high accuracy methane standards compared well to expected concentrations (3% relative error), (2) a gas-phase benzene standard was generated using a permeation source and measured by TOC and gas chromatography mass spectrometry (GC-MS) with excellent agreement (<4% relative difference), and (3) total carbon measurement of 4 known gas phase mixtures were performed and compared to a calculated carbon content to agreement within the stated uncertainties of the standards. Measurements from laboratory biomass burning experiments of formic acid by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS) and formaldehyde by proton transfer reaction-mass spectrometry (PTR-MS), both calibrated using MOCCS, were compared to open path Fourier transform infrared spectroscopy (OP-FTIR) to validate the MOCCS calibration and were found to compare well (R 2 of 0.91 and 0.99, respectively).

Calibration and intercomparison of acetic acid measurements using proton-transfer-reaction mass spectrometry (PTR-MS)

“…Known mixing ratios of acetic acid were generated by diluting pure acetic acid emitted from a permeation tube (Kin-Tek Inc.) that was gravimetrically certified (103 ± 5 % ng min −1 at 30 • C) by the manufacturer. The high dilution flow rates yielded stable acetic acid calibration gas streams at low ppbv levels, within the range of those in ambient air, and much less than ppmv level standards typically generated by other techniques (Veres et al, 2010). The dilution flow (F dil ) was used to control the mixing ratio of acetic acid in the calibration gas.…”

Formation of Low Volatility Organic Compounds and Secondary Organic Aerosol from Isoprene Hydroxyhydroperoxide Low-NO Oxidation

“…9 To track system stability and repeatability, a signal calibration was performed periodically, before or after experiments, by flowing a steady concentration of diethylene glycol (DEG) for several minutes, which was quantified using a catalytic converter and CO 2 analyzer following the method of Veres et al 5 The instrument showed excellent stability and repeatability.…”

“…The CO 2 was then measured using a LI-840A CO 2 analyzer (LI-COR). 5 The FIXCIT inlet was used in the calibrations to maintain the same f inlet values. Malonic acid (C 3 H 4 O 4 ) was the most sensitive organic compound tested and was used as the primary LVOC calibrant since it is thought to cluster at rates close to the collision limit 6 .…”

Measurement of HONO, HNCO, and other inorganic acids by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS): application to biomass burning emissions

“…A formic acid standard was added to the system to provide a baseline measure of instrument sensitivity throughout the biomass burning experiments and the subsequent laboratory studies of the inorganic acids. The formic acid source consisted of a thermostatted permeation tube that was routinely measured by catalytic conversion to CO 2 and non-dispersive infrared spectroscopy (NDIR) (Veres et al, 2010a). Nitric acid was also added to the system with a permeation tube, the calibration of which was accomplished by UV absorption spectroscopy as described by Neuman et al (2003).…”