Chamber validation study of simultaneous collection and analysis of aromatic diisocyanates and the corresponding diamines using the ASSET-ICA sampler

Simultaneous sampling of diisocyanates and diamines is of great importance since occupational exposure to both diamines and diisocyanates may occur during production of the diisocyanates and polyurethane (PU) products or during thermal degradation of PU material. A methodology for the simultaneous collection and determination of diisocyanates and diamines using ASSET EZ4-ICA dry sampler (Supelco, PA, United States) was presented. The sampler was previously validated and is sold commercially for isocyanate detection. This work investigated to also include diamine determinations (specifically MDA and TDA) to enable a user-friendly approach, without the use of fragile glassware and solvents during sampling. In addition, a sampler based on the same design as the ASSET-sampler but with a modified impregnation with dibutyl amine (DBA) and sulfuric acid was also demonstrated. During sampling, isocyanates were collected and derivatized with DBA and the diamines were derivatized in a subsequent work-up procedure with ethyl chloroformate to form carbamate esters. For the ASSET-ICA sampler, no breakthrough was observed for 2,4'-MDA or 4,4'-MDA for sampling at 200 mL/min for up to 4 h (240 min). For 2,4-TDA and 2,6-TDA, no breakthrough was observed for up to 60 min of sampling. For the sampler with modified impregnation, no breakthrough of TDA was observed for up to 240 min of sampling. No losses were observed for the MDA isomers when storing the samplers in a refrigerator (8 °C) for up to 21 d after sampling. However, for the TDA isomers, minor losses could be observed after storage for 8 d. Storing the samplers in a freezer (-18 °C) or performing the addition of 500 µL of 3M sulphuric acid to the sampler filter media after sampling improved the stability of the TDA isomers during storage and no losses were observed for 21 d of storage. Also, for the sampler with modified impregnation, storage for up to 21 d could be made without any significant losses of TDA. Comparable concentrations were measured in ASSET-ICA samplers and in impinger-filter samples when sampling of a controlled test atmosphere was performed at different relative humidity (30% to 70% RH) and also during sampling of thermal degradation products from PU foam.