| 1. |
- Gustavsson, Marcus, et al.
(författare)
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Adsorption Efficiency of Respirator Filter Cartridges for Isocyanates
- 2010
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Ingår i: Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 0003-4878 .- 1475-3162. ; 54:4, s. 377-390
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Tidskriftsartikel (refereegranskat)abstract
- In some industries, the temperature and the humidity will vary greatly between different work places, such as outdoor work in arctic or tropical climates. There is therefore a need to test respirator filters at conditions that simulate conditions that are relevant for the industries that they are used in. Filter cartridges were exposed to controlled atmospheres of varying isocyanate concentration, air humidity, and temperature in an exposure chamber. For isocyanic acid (ICA) and methyl isocyanate (MIC), the exposure concentrations were between 100 and 200 p.p.b., monitored using a proton transfer reaction mass spectrometer. ICA and MIC were generated by continuous thermal degradation of urea and dimethylurea. The breakthrough was studied by collecting air samples at the outlet of the filter cartridges using impinger flasks or dry samplers with di-n-butylamine as derivatization reagent for isocyanates followed by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. For hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI), the exposure concentrations were between 4 and 20 p.p.b. and were generated by wet membrane permeation. To reveal the profile of adsorption in different layers of the respirator filters, representative samples from each of the layers were hydrolyzed. The hydrolysis products hexamethylene diamine and isophorone diamine were determined after derivatization with pentafluoropropionic anhydride (PFPA) followed by LC-MS/MS analysis. The two filter types studied efficiently absorbed both ICA and MIC. There was no trend of impaired performance throughout 48-h exposure tests. Even when the filters were exposed to high concentrations (similar to 200 p.p.b.) of ICA and MIC for 96 h, the isocyanates were efficiently absorbed with only a limited breakthrough. The majority of the HDI and IPDI (> 90%) were absorbed in the top layers of the absorbant, but HDI and IPDI penetrated farther down into the respirator filters during 120 h of exposure as compared to 16 h exposure.
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| 2. |
- Gylestam, Daniel, 1979-, et al.
(författare)
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Sampling of Respirable Isocyanate Particles
- 2014
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Ingår i: Annals of Occupational Hygiene. - : Oxford University Press (OUP). - 0003-4878 .- 1475-3162. ; 58:3, s. 340-354
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Tidskriftsartikel (refereegranskat)abstract
- An advanced design of a denuder impactor (DI) sampler has been developed for characterization of possible airborne isocyanate exposure in different particle size fractions. The sampler is equipped with 12 different parallel denuder tubes, 4 impaction stages with the cut-off values (d50) of: 9.5, 4, 2.5 and 1 µm, and an end filter that collects particles < 1 µm. All collecting parts were impregnated with di-n-butylamine DBA as the reagent in a mixture with acetic acid. The performance of the DI sampler was studied on a standard atmosphere containing gas and particulate isocyanates. The isocyanate atmosphere was generated by liquid permeation of 2,4-, 2,6-Toluene Diisocyanate (TDI), 1,6-Hexamethylene Diisocyanate (HDI) and Isophorone Diisocyanate (IPDI). 4,4’-Methylene Diphenyl Diisocyanate (MDI) particles were generated by heating of technical MDI and condensing the mixture of gas and particle-borne MDI in an atmosphere containing mixed salt particles. The study was performed in a 0.85 m3 environmental chamber with stainless steel walls. With the advancement of the DI sampler it is now possible to collect isocyanate particle samples for up to 320min. The performance of the DI sampler is essentially unaffected by the humidity. The DI sampler and the ASSET™ EZ4-NCO sampler (Sigma-Aldrich/Supelco, Bellefonte, PA, USA) gave similar results. Sample losses within the DI sampler are low. In the environmental chamber it was observed that the particle distribution may be affected by the humidity and ageing. A scanning mobility particle sizer (SMPS) was used to separate a flow of selected fractions containing MDI particles from mixed MDI and salt particles. The particle-size distribution had a maximum at about 300nm, but later in the environmental chamber 1 µm dominated. The distribution was very different as compared to with only NaCl or MDI present. The biological relevance for studying isocyanate nano particles is significant as these have the possibility to reach the lower airways where allergic reactions may occur. SMPS and isocyanate air sampling can be used for the investigation of isocyanate nano particles.
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