Marianne Dalene

Size-separated sampling and analysis of isocyanates in workplace aerosols : Part II: Aging of aerosols from thermal degradation of polyurethane

A new type of isocyanate sampler has been used to investigate aging aerosols generated during thermal degradation of polyurethane (PUR). The sampler consists of a denuder connected in series with a three-stage cascade impactor and a filter. The denuder collects gas-phase isocyanates. The three impactor stages had cut-off diameters (d(50)) of 2.5, 1.0 and 0.5 mum, respectively. The end filter collects particles <0.5 mum. For derivatization of isocyanates in the sampler, di-n-butylamine mixed with an equimolar amount of acetic acid was used for impregnation of the sampler stages. Consecutive sampling using three denuder-impactor samplers was performed in a test chamber, with a total sampling time of 9 min. Analysis of air samples was performed using liquid chromatography-mass spectrometry (LC-MS)/MS. Particle size measurements were performed using a scanning mobility particle sizer (SMPS). A time-dependent behavior was observed for aromatic diisocyanates during aging of the aerosol. Thermal degradation of different PUR materials showed different distribution of isocyanates between gas and particles. Aromatic diisocyanates (toluene diisocyanate (TDI) and methylene diphenyl diisocyanate) were initially in gas phase and associated to very small particles. After a few minutes most of these isocyanates were associated with particles <1 mum. Monoisocyanates and hexamethylene diisocyanate (HDI) were not found to be associated with particles.

Size-Separated Sampling and Analysis of Isocyanates in Workplace Aerosols. Part I. Denuder—Cascade Impactor Sampler

Isocyanates in the workplace atmosphere are typically present both in gas and particle phase. The health effects of exposure to isocyanates in gas phase and different particle size fractions are likely to be different due to their ability to reach different parts in the respiratory system. To reveal more details regarding the exposure to isocyanate aerosols, a denuder-impactor (DI) sampler for airborne isocyanates was designed. The sampler consists of a channel-plate denuder for collection of gaseous isocyanates, in series with three-cascade impactor stages with cut-off diameters (d(50)) of 2.5, 1.0 and 0.5 mum. An end filter was connected in series after the impactor for collection of particles smaller than 0.5 mum. The denuder, impactor plates and the end filter were impregnated with a mixture of di-n-butylamine (DBA) and acetic acid for derivatization of the isocyanates. During sampling, the reagent on the impactor plates and the end filter is continuously refreshed, due to the DBA release from the impregnated denuder plates. This secures efficient derivatization of all isocyanate particles. The airflow through the sampler was 5 l min(-1). After sampling, the samples containing the different size fractions were analyzed using liquid chromatography-mass spectrometry (LC-MS)/MS. The DBA impregnation was stable in the sampler for at least 1 week. After sampling, the DBA derivatives were stable for at least 3 weeks. Air sampling was performed in a test chamber (300 l). Isocyanate aerosols studied were thermal degradation products of different polyurethane polymers, spraying of isocyanate coating compounds and pure gas-phase isocyanates. Sampling with impinger flasks, containing DBA in toluene, with a glass fiber filter in series was used as a reference method. The DI sampler showed good compliance with the reference method, regarding total air levels. For the different aerosols studied, vast differences were revealed in the distribution of isocyanate in gas and different particle size fractions. The opportunity to obtain detailed information regarding the distribution of isocyanates in aerosols in addition to the total air levels make the DI sampler a valuable tool for studies of possible health effects in the different parts of the airways.

Dry Sampling of Gas-Phase Isocyanates and Isocyanate Aerosols from Thermal Degradation of Polyurethane

The performance of a dry sampler, with an impregnated denuder in series with a glass fibre filter, using di-n-butylamine (DBA) for airborne isocyanates (200ml min(-1)) is investigated and compared with an impinger flask with a glass fibre filter in series (1 l min(-1)). An exposure chamber containing 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and 2,4- and 2,6-toluene diisocyanate (TDI) in the concentration range of 5-205 μg m(-3) [0.7-33 p.p.b.; relative humidity (RH) 50%], generated by gas- and liquid-phase permeation, was used for the investigation. The precision for the dry sampling for five series with eight samplers were in the range of 2.0-6.1% with an average of 3.8%. During 120-min sampling (n = 4), no breakthrough was observed when analysing samplers in series. Sixty-four exposed samplers were analysed after storage for 0, 7, 14, and 21 days. No breakdown of isocyanate derivatives was observed. Twenty-eight samplers in groups of eight were collecting isocyanates during 0.5-32h. Virtually linear relationships were obtained with regard to sampling time and collected isocyanates with correlation coefficients in the range of 0.998-0.999 with the intercept close to the origin. Pre- or post-exposure to ambient air did not affect the result. Dry sampling (n = 48) with impinger-filter sampling (n = 48) of thermal decomposition product of polyurethane polymers, at RH 20, 40, 60, and 90%, was compared for 11 isocyanate compounds. The ratio between the different isocyanates collected with dry samplers and impinger-filter samplers was in the range of 0.80-1.14 for RH = 20%, 0.8-1.25 for RH = 40%, 0.76-1.4 for RH = 60%, and 0.72-3.7 for RH = 90%. Taking into account experimental errors, it seems clear that isocyanic acid DBA derivatives are found at higher levels in the dry samples compared with impinger-filter samplers at elevated humidity. The dry sampling using DBA as the reagent enables easy and robust sampling without the need of field extraction.

Adsorption Efficiency of Respirator Filter Cartridges for Isocyanates

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 (approximately 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.

Analysis of Aqueous Alkanolamines Using Hydrophilic Interaction Liquid Chromatography and Mass Spectrometry

A method based on zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) and mass spectrometry (MS) is presented for determination of mono-, di-, triethanolamine (EA, DEA, TEA), iso-, N-propanolamine (IPA, NPA), diisopropyl ethanol amine (DIPEA), 2-diethylethanol amine (DEEA), diisopropanol amine (DIPA), dimethylethanol amine (DMEA), N-methyldiethanol amine (MDEA) in aqueous solutions. Linear calibration graphs (0.04-3.0 µg mL-1, n=9) were obtained with correlation coefficients in the range of >0.96 using N-tripropyl amine (NTPN) as internal standard and >0.99 using NPA as internal standard. The instrumental detection limit was below 44 fmol. Chromatographic separation of the 10 studied alkanolamines was achieved. Injection volumes up to 3 µL was enabled using on-column. The optimal solvent composition was found to be 100 % water with 0.01 % acid at pH<4. Sample solution concentrations of 1.0 µg mL-1 could be injected on the column with sustained chromatography.

Determination of Cotinine in Urine and Saliva Using Hydrophilic Interaction Liquid Chromatography and Tandem Mass Spectrometry

Abstract A new simplified method for monitoring of cotinine in urine and saliva, based on hydrophilic interaction liquid chromatography (HILIC) and tandem mass spectrometry (MS) is presented. Work-up techniques based on filtration, using 0.45 μm pore sizepolypropylene filter, of crude urine and saliva and alkaline extraction of cotinine with methylene dichloride were studied. Multiple reaction monitoring (MRM) of the protonated molecular ions of cotinine and tri-deuterium labelled cotinine resulted in selective determinations with linear calibration graphs (correlation coefficients >0.999) The precision for 10 samples, containing 100 ng cotinine /ml, prepared from urine and saliva by methylene dichloride extraction or filtration were between 2 and 5 %. The detection limit for extracted and filtrated saliva was 2 fmol and for extracted and filtrated urine it was 5 and 9 fmol, respectively. Agreement was obtained for the two different work-up techniques. Extraction of urine/saliva enabled detection at lower levels (down to 5 pg cotinine/ml of urine) compared to filtration, since the possibility of enrichment of the sample but also due to reduction of interfering compounds present in the matrix. However, when performing large exposure studies with many samples to be analysed, the simplified and time saving work-up procedure obtained with filtration is valuable. The higher organic content of the effluent in the HILIC mode and a more efficient separation of polar compounds present in the matrix, favoured the electrospray ionisation compared to reversed phase (RP) LC, thus enabling lower detection limits.