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Issue 10, 2014
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The applicability of proton transfer reaction-mass spectrometry (PTR-MS) for determination of isocyanic acid (ICA) in work room atmospheres

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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 (R2 > 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.

Graphical abstract: The applicability of proton transfer reaction-mass spectrometry (PTR-MS) for determination of isocyanic acid (ICA) in work room atmospheres

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Publication details

The article was received on 30 Jun 2014, accepted on 18 Aug 2014 and first published on 19 Aug 2014


Article type: Paper
DOI: 10.1039/C4EM00363B
Environ. Sci.: Processes Impacts, 2014,16, 2423-2431

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    The applicability of proton transfer reaction-mass spectrometry (PTR-MS) for determination of isocyanic acid (ICA) in work room atmospheres

    M. J. Jankowski, R. Olsen, C. J. Nielsen, Y. Thomassen and P. Molander, Environ. Sci.: Processes Impacts, 2014, 16, 2423
    DOI: 10.1039/C4EM00363B

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