Comprehensive comparison of sampling methods for evaluating hexamethylene diisocyanate (HDI) in the air of an automotive collision repair facility.

A methodology for workplace air monitoring of aromatic and aliphatic, mono- and polyisocyanates by derivatisation with di-n-butylamine (DBA) is presented. Air sampling was performed using midget impinger flasks containing 10 ml of 0.01 mol l(-1) DBA in toluene and a glass-fibre filter in series after the impinger flask, thereby providing the possibility of collecting and derivatising isocyanates in both the gas and particle phases. Quantification was made by LC-MS, monitoring the molecular ions [MH]+. Air samples taken with this method in car repair shops showed that many different isocyanates are formed during thermal decomposition of polyurethane (PUR) coatings. In addition to isocyanates such as hexamethylene (HDI), isophorone (IPDI), toluene (TDI) and methylenediphenyl diisocyanate (MDI), monoisocyanates such as methyl (MIC), ethyl (EIC), propyl (PIC), butyl (BIC) and phenyl isocyanate (PhI) were found. In many air samples the aliphatic monoisocyanates dominated. During cutting and welding operations, the highest levels of isocyanates were observed. In a single air sample from a welding operation in a car repair shop, the highest concentrations found were: MIC, 290; EIC, 60; PIC, 20; BIC, 9; PhI, 27; HDI, 105; IPDI, 39; MDI, 4; and 2,4-TDI and 2,6-TDI 140 microg m(-3). Monitoring the particle size distribution and concentration during grinding, welding and cutting operations showed that ultrafine particles (< 0.1 microm) were formed at high concentrations. Isocyanates with low volatility were mainly found in the particle phase, but isocyanates with a relatively high volatility such as TDI, were found in both the particle and gas phases.

Validation of Transferability of DBA Derivatization and LC–MS/MS Determination Method for Isocyanates via an Interlaboratory Comparison

Washing the clothes of cat owners is a simple method to prevent cat allergen dispersal

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

Enhancement of the cycling stability of lithium-sulfur batteries by using a reactive additive for blocking dissolution of lithium polysulfides

91 Isocyanates Aerosols Sampling for Occupational Exposures Assessment

An air sampling method for the determination of isocyanates, aminoisocyanates and amines formed during the thermal degradation of polyurethane (PUR) is presented. The method is based on the collection of air samples using impinger flasks containing di-n-butylamine (DBA) in toluene with a glass fibre filter in series. Isocyanates are derivatized with DBA to urea derivatives, and amines are derivatized in a subsequent work-up procedure with ethyl chloroformate (ET) to carbamate esters. Amine, aminoisocyanate and isocyanate derivatives were characterized using liquid chromatography-time of flight mass spectrometry (LC-TOFMS) and liquid chromatography-chemiluminescent nitrogen detection (LC-CLND). Quantification was performed by LC-MS, monitoring molecular ions [MH]+ in the electrospray mode. The instrumental detection limits for amines, aminoisocyanates and isocyanates were in the ranges 30-40, 2-3 and 3-70 fmol, respectively. Thermal degradation products of PUR were observed in high concentrations during welding in district heating pipes and PUR-coated metal sheets. Eleven isocyanates, three amines and five aminoisocyanates were identified. The concentrations of isocyanates, aminoisocyanates and amines in samples collected in the smoke close to the welding spot were in the ranges 150-650, 4-290 and 1-70 ppb, respectively. In samples collected in the breathing zone, isocyanates and aminoisocyanates were observed in the ranges 9-120 and 4-19 ppb, respectively. The compounds were present in both gas and particle phases. Volatile compounds dominated in the gas phase, whereas less volatile compounds dominated in the particle phase. The method presented makes it possible to sample and determine amines and aminoisocyanates, in addition to isocyanates. The need to monitor these compounds is clearly illustrated by the high concentrations found during the thermal degradation of PUR.

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

Diffusive sampling of methyl isocyanate (MIC) on 4-nitro-7-piperazinobenzo-2-oxa-1,3-diazole (NBDPZ)-coated glass fibre (GF) filters is strongly affected by high relative humidity (RH) conditions. It is shown that the humidity interference is a physical phenomenon, based on displacement of reagent from the filter surface. In this paper, this drawback has been overcome by changing the filter material to the less polar polystyrene divinyl benzene (SDB). A series of experiments was performed to compare the analyte uptake on the two filter materials for different sampling periods and analyte concentrations at both low and high RH conditions. Additionally, the materials were investigated as well for passive sampling of ethyl (EIC) and phenyl isocyanate (PhIC) with NBDPZ and 1-(2-methoxyphenyl) piperazine (2-MP) as an alternative derivatising agent. Using 2-MP, the mean GF/SDB response ratios were determined to be 1.02 for MIC (RSD: 6.1%) and 1.03 for EIC (RSD: 6.8%), whereas PhIC could only be determined on SDB filters. Using NBDPZ as reagent, the negative influence of high humidity disappeared when SDB filters were used instead of GF filters. Even at low RH conditions, sampling with SDB material generally resulted in a higher analyte uptake than with GF filters. The GF/SDB response ratios were independent of sampling time or analyte concentration and were determined to be 0.70 (RSD: 4.7%) for MIC, 0.84 (RSD: 4.5%) for EIC and 0.95 (RSD 5.4%) for PhIC, meaning that the NBDPZ diffusive sampler based on SDB can be used at all humidity conditions without any restrictions.

The partitioning of photosynthetically-derived organic carbon between particulate and dissolved phases has important implications for marine carbon cycling. In this study we utilized 14C-bicarbonate assimilation to quantify rates of photosynthetic production of both particulate and dissolved organic carbon (DOC) at Station ALOHA (22˚45’N, 158˚W) in the North Pacific Subtropical Gyre (NPSG). At near-monthly time scales over ~5 years, we examined retention of 14C-labeled organic matter by both glass fiber filters and 0.2 µm pore size polycarbonate membrane filters that are commonly used for measurements of 14C-based plankton productivity. Use of polycarbonate filters resulted in significantly lower (averaging 60%) estimates of 14C-production compared to glass fiber filters. Coincident measurements of chlorophyll a concentrations from both 0.2 µm polycarbonate and glass fiber filters were not significantly different, suggesting the differences in 14C-productivity between these filter-types did not derive from differences in retention of photosynthetic biomass by these filters. Moreover, consistent with previous studies, results from experiments aimed at quantifying retention of organic matter by these filters suggested the difference between these two types of filters resulted from retention of DOC by glass fiber filters. We also quantified rates of 14C-DOC production to evaluate the partitioning of photosynthetic production between dissolved and particulate phases over daily to monthly time scales in this ecosystem. Unlike the strong depth-dependence observed in measurements of particulate organic carbon production, measured rates of 14C-DOC demonstrated no clear depth-dependence. On average, depth-integrated (0-75 m) rates of 14C-DOC production rates were equivalent to 18 ± 10% of the total (particulate and dissolved) productivity. Our findings indicate that in this oligotrophic ecosystem, rates of dissolved and particulate production can be temporally decoupled over daily to monthly time scales.

Relative differences in reactivity between reagents (all of which are secondary amines) particularly affect polyfunctional isocyanates, such as hexamethylene diisocyanate (HDI) and tolylene diisocyanate (TDI), compared with monoisocyanates. Thus, in 1994–1995, we carried out a programme of work to study the relative reactivity of the standard reagents, and of two alternative derivatising agents, by performing comparison tests on reaction rates. In the meantime, the reactivity of standard reagents used internationally for the determination of isocyanates in workplace atmospheres, as compared with some proposed “more reactive” alternative competitors, has been addressed by various authors. We measured the relative rates of reactions (partial rate factors) using the monomeric diisocyanates HDI and TDI and the monoisocyanate phenylisocyanate (PHI) separately in absorber solutions containing twin mixtures of different reagents. The partial rate factors of the reactions were found to vary by orders of magnitude using the diisocyanates HDI and TDI. They show a dependence on the chemical structure. Using the monoisocyanate PHI, our experimental results are consistent with literature data. Furthermore, our results clearly demonstrate that the proposed “most reactive” reagent dibutylamine (DBA) is less reactive towards HDI and TDI than is the reagent 1-(2-methoxyphenyl)piperazine (2-MP). In spite of the different reaction rates found, in our experience, up to now, there is “no-effect” on the analytical results when comparison tests are performed by monitoring isocyanates in air using DBA and the well known standard reagents. Work continues and results will be given in a following paper.

Isocyanates are well-known irritants and sensitizers, and measuring their occupational airborne exposure is challenging due to their high chemical reactivity and semi-volatile nature. This study builds on a previous publication by our team that focused on comparing evaluation methods for isocyanates. The current research aims at developing, validating, and applying a laboratory generation system designed to replicate real-world conditions for spraying clear coats in autobody shops using hexamethylene diisocyanate (HDI)-based products. The system involved a spray gun connected to two chambers in series, enabling sample collection and analysis. The system successfully generated HDI and isocyanurate concentrations ranging from 0.008 to 0.040 mg m-3 and 0.351 to 3.45 mg m-3, respectively, with spatial homogeneity (RSD) of 5.8% and 16.5%. The particle-size distribution (MMAD) of 4 μm was measured using a cascade impactor and an electrical low-pressure impactor. The samples generated were used to correlate the amount of isocyanates collected with scanning electron microscope images of droplets on a filter. Three methods were compared to the reference method-an impinger with a backup glass fibre filter (GFF) and 1,2-methoxyphenylpiperazine (MP) based on ISO 16702/MDHS 25-in six generation experiments: (1) Swinnex cassette 13 mm GFF MP (MP-Swin); (2) closed-face cassette 37 mm GFF (end filter and inner walls) MP (MP-37); and (3) denuder and GFF dibutylamine (DBA) (ISO 17334-1 Asset). The analysis revealed clear trends regarding which sampler sections collected HDI (mainly in the vapor phase) or isocyanurate (exclusively in the particulate phase). The study found no significant bias between the tested methods (MP-Swin, MP-37, and Asset) and the reference method (impinger) for both HDI monomer and isocyanurate. The three tested methods showed limits of agreement beyond the acceptable range of ±30% (95% confidence interval), largely due to data variability, though MP-Swin and MP-37 exhibited lower variability than Asset. The results will be further evaluated in a real-world environment where similar clear coats are used.

An LC–MS method is presented for the determination of aliphatic isocyanate [hexamethylene diisocyanate] (HDI), isophorone diisocyanate (IPDI), biuret and isocyanurate] adducts of HDI as their dibutylamine (DBA) derivatives. The method is based on sampling in midget impinger flasks containing 10 ml of 0.01 mol l–1 DBA in toluene (see parts 1–3 of this series†). The excess reagent and the solvent are removed by evaporation. The enriched samples are then analysed using LC–electrospray MS. Quantification of HDI–DBA and IPDI–DBA was effected by monitoring the molecular ion [MH]+. Linear calibration graphs were obtained in the range 50–500 nmol l–1 with correlation coefficients of 0.9965–0.9997. The RSD for samples spiked at a concentration of 1 nmol l–1 was 1.7 and 2.9% for the two IPDI–DBA isomers (n = 8) and 1.2% for HDI–DBA (n = 8). On injecting 4 µl of the 0.5 ml sample, the instrumental detection limit was about 20 nmol l–1, which corresponds to about 0.1 µg m–3 for HDI and 0.2 µg m–3 for IPDI for a 15 l air sample.No degradation was observed after storage of the derivatives for up to 4 months in acetonitrile or toluene. No losses were seen when the derivatization reaction took place in the presence of interferents such as morpholine, hexamethylenediamine, isophoronediamine and phenol corresponding to concentrations of 10 ppm in air for a 15 l air sample. The influence of water was studied by spiking with volumes corresponding to a relative humidity of 80% at 30 °C in 15 l of air. The reaction rates of HDI and IPDI with DBA were found to be 2–3 times faster than those for 1-(2-methoxyphenyl)piperazine.

Pesticides can enter the atmosphere during spraying or after application, resulting in environmental or human exposure. The study describes the optimisation and validation of analytical methods for the determination of more than 300 pesticides in the particulate and gaseous phases of the air. Pesticides were sampled with high-volume air samplers on glass-fibre filters (GFFs) and glass columns filled with polyurethane foam (PUF) and XAD-2 resin. Comparing different extraction methods, a QuEChERS extraction with acetonitrile was selected for the GFFs. For the PUF/XAD-2 columns, a cold-column extraction with dichloromethane was used. Instrumental determination was performed using liquid chromatography/electrospray ionisation-time-of-flight mass spectrometry (LC/ESI-QTOF) and gas chromatography/electron impact ionisation-tandem mass spectrometry (GC/EI-MS/MS). Recovery experiments showed recovery rates between 70 and 120% for 263 compounds on the GFFs and 75 compounds on the PUF/XAD-2 columns. Semi-quantitative determination was performed for 39 compounds on the GFFs and 110 compounds on the PUF/XAD-2 columns. Finally, 27 compounds on the GFFs and 138 compounds on the PUF/XAD-2 columns could be determined only qualitatively. For the determination of the PUF/XAD-2 samples, signal suppression (LC) or signal enhancement (GC) due to matrix effects were determined. Method quantification limits of the optimised methods ranged from 30 to 240 pg/m3 for the target compounds on the GFFs, and from 8 to 60 pg/m3 on the PUF/XAD-2 columns. The applicability of the method was demonstrated by means of environmental air samples from an agricultural area in the Netherlands.

Aerogel preparation of MgO and CaO nanoparticles involves a sol−gel approach where methoxides are converted to hydroxide gels followed by hypercritical drying and vacuum dehydration. This produces, for these particular hydroxides/oxides, ultrafine particulates rather than monoliths. These particulate materials have exhibited unexpectedly high surface chemical reactivities that have allowed their successful use as high-capacity destructive adsorbents for toxic chemicals, including chlorocarbons, organophosphorus compounds, and acid gases. Detailed characterization involving X-ray diffraction (XRD), gas adsorption/pore distribution analysis, infrared, TEM, AFM, XPS, probe molecule adsorption, and elemental analysis has allowed a rationale to be developed that helps explain the high chemical reactivities observed, especially for CaO. Pore volume and size distribution, unusual surface morphologies with a high ratio of edge ion/surface ions, and trace residual (persistent) surface −OH and −OCH3 seem to be the main factors allowing these nanoparticulates to be isolable and stable and yet highly reactive, and results for CaO are emphasized herein.