title: The applicability of proton transfer reaction-mass spectrometry (PTR-MS) for determination of isocyanic acid (ICA) in work room atmospheres.
abstract: A method is presented for the real-time quantitative determination of isocyanic acid (ICA) in air using proton transfer reaction-mass spectrometry (PTR-MS). Quantum mechanical calculations were performed to establish the ion-polar molecule reaction rate of ICA and other isocyanates. The PTR-MS was calibrated against different ICA air concentrations and humidity conditions using Fourier transform-infrared spectroscopy (FT-IR) as quantitative reference. Based on these experiments a simple humidity dependant model was derived for correction of the PTR-MS response for ICA. The corrected PTR-MS data was linearly correlated (R(2) > 0.99) with the data acquired by FT-IR. The PTR-MS instrumental limit of detection (LOD) for ICA was 2.3 ppb. Humid atmospheres resulted in LODs of 3.4 and 7.8 ppb, at an absolute humidity (AH) of 4.0 and 15.5 g m(-3), respectively. Furthermore, off-line sampling using denuder and impinger samplers using di-n-butylamine (DBA) as derivatization reagent was compared with PTR-MS measurements in a dynamically generated standard ICA atmosphere. Denuder (n = 4) and impinger (n = 4) sampling subsequent to liquid chromatography mass spectrometry (LC-MS) determination compared to corrected PTR-MS data resulted in recoveries of 79.6 (8.1% RSD) and 99.9 (9.3% RSD) %, respectively. Measurements of ICA from thermally decomposed cured 1,6-hexamethylene diisocyanate (HDI)-paint was performed using PTR-MS and denuder (n = 3) sampling. The relation between the average ICA responses using denuders (34.4 ppb) and PTR-MS (42.6 ppb) was 80.6%, which coincided well with the relative recovery obtained from the controlled laboratory experiments using dynamically generated ICA atmospheres (79.6%). The variability in ICA air concentration during the welding process (170% RSDPTR-MS) illustrated the need for real-time measurements.
authors.affiliation: National Institute of Occupational Health, P.O. Box 8149, Oslo N-0033, Norway. mikolaj.j.jankowski@stami.no.
authors.forename: Mikolaj Jan
authors.initials: MJ
authors.lastname: Jankowski
authors.forename: Raymond
authors.initials: R
authors.lastname: Olsen
authors.forename: Claus Jørgen
authors.initials: CJ
authors.lastname: Nielsen
authors.forename: Yngvar
authors.initials: Y
authors.lastname: Thomassen
authors.forename: Paal
authors.initials: P
authors.lastname: Molander
mesh_terms: D000395:Air Pollutants, Occupational / Q000032:analysis*; D003485:Cyanates / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods*; D013058:Mass Spectrometry
chemical_list: D000395:Air Pollutants, Occupational; D003485:Cyanates; C005057:isocyanic acid