Air Monitoring

Introducing the New ASSET-EZ4 ICA Dry Sampler for Measurement of Isocyanic Acid and Related Compounds During an Industrial Process

Dec 14 2016 Read 974 Times

Isocyanic acid (ICA) is the smallest member among isocyanate compounds. It’s known to be produced during the process of burning of fossil fuels; as well as during forest fires and woodburning [2]. Heating of polyurethane materials (PU), plastics and coatings derived from isocyanates will also generate small molecular weight isocyanates including ICA and methylisocyanate (MIC) [3]. For this study, ASSET EZ4-ICA was used to measure the air during the industrial process for manufacturing insulation.

Previously, a dry sampler was presented which is used to capture and derivatize a variety of isocyanate compounds [3]. It’s called ASSET™ EZ4-NCO and uses dibutylamine as a derivatization and capturing agent. However, the inherent background of ICA is too high to enable accurate measurement of ICA during sampling periods shorter than four hours.

To address the high ICA background constraint, a new sampler was developed and designed specifically for sampling ICA. Its low background levels allow for the quantitation of ICA for short term sampling, as short as five minutes. To evaluate its performance, it was used to collect air samples for both ICA and MIC from a production line at an insulation manufacturing facility. During production, the starting material is heated up to 270ºC, and ICA and MIC are released into the air as byproducts. The ASSET EZ4-ICA samplers were placed next to the fully automated process and sampling was performed by the certified Occupational Hygienist. During sampling, each sampler was connected to a low flow pump and the air flow was set at 200 mL/min. The flow rate of the pumps was verified before and after sampling. Samples were collected at five minutes, one hour and four hour time intervals. The temperature and humidity of the air during the sampling was 27ºC and 25%, respectively. Duplicate samples were taken for each time study. After sampling was completed, the samplers were capped and shipped to the analytical laboratory where they were extracted and analysed via LC/MS/MS.

Field blank samples were also collected by exposing the samplers to the air in the production facility, the office area and the laboratory by removing and reinstalling the caps of the samplers. No detectable amounts of ICA or MIC were found.

The ASSET EZ4-ICA sampler was successfully used for sampling the air during the insulation manufacturing process. The sampler was found to be excellent for measuring both ICA and MIC for the short five-minute samples, since it exhibits low background (<0.005 µg levels from blank samplers). It was found that the sampler may have reached its capacity after two hours of sampling at 200 mL/min flow rate since high concentrations of the ICA were produced during the production process. The highest concentration of ICA measured during the span of one-hour time was 404 µg/m³ and for MIC the highest measured concentration was 22.5 µg/m³. This study suggests ASSET EZ4-ICA samplers can be used to collect ICA and/or MIC for sampling times up to two hours when sampling at a flow rate of 200 mL/min.

To read more about this study, please click here.


1. Brady J. M., et al. Environ. Sci. Technol. 2014, 48, 11405-11412
2., accessed  12/2/2015
3. Karlsson, D., Dalene, M., Scarping, G., Marand, A. J. Environ. Monit. 2001, 3, 432-436.

The work described here was performed by M. Andersson, L. Andersson and N. Johansson at Department of Occupational and Environmental Medicine, Örebro, Sweden.

ASSET is a trademark of Sigma-Aldrich Co. LLC.

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