This method has been temporarily withdrawn due to unreliable supply of analytical standards


Isocyanates are a group of highly reactive chemicals that are widely used in manufacture of coatings, foams, elastomers and construction materials. Without proper personal protective equipment, respiratory exposure to products containing isocyanates has lead to many work-related illnesses including severe asthma and even death. Historically in the UK, the method of measuring airborne Isocyanates has been MDHS 25/4, which uses the derivatising agent 1-(2-methoxyphenyl) piperazine to convert isocyanates into a stable and less volatile form.


World regulatory update

Piperazine compounds are used in a variety of isocyanate sampling devices as derivatisation agents to convert the reactive isocyanates into stable compounds that can be analysed by HPLC. In the United Kingdom, early in 2013, piperazine compounds were declared controlled substances due to their increasing use as precursors in the manufacturing of designer drug formulations. Therefore the 1-(2- methoxyphenyl)piperazine used in the UK MDHS 25/4 and ISO-CHEK® filters/solutions, the 1,2-pyridyl piperazine (PP) wet sampler for OSHA methods 42 & 47, as well as the impinger solution containing 1-(9-anthracenylmethyl) piperazine (MAP) for NIOSH 5525 cannot be supplied to occupational hygienists without first obtaining the appropriate licenses.


The Future

MSSL offer to supply and analyse Isocyanates samples taken onto Supelco ASSET™EZ4 Dry Samplers for Isocyanates.

The ASSET EZ4 Dry Sampler is safe for the worker to use for personal sampling because it requires no field addition of reagents, no field extraction, and no special storage requirements. In addition, it is the only sampling device that achieves reliable low detection limits compared to existing commercially available devices. The ASSET EZ4 sampling device is a unique dry sampler based on derivatization of isocyanate groups with di-n-butylamine (DBA). The sampler consists of a denuder and a filter, both impregnated with DBA. The extract is analysed using LC-MS/MS offering the ultimate sensitivity and lower detection limits than other methods, including MDHS 25/4.

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The advantages

  • Increased worker productivity, no need to take the worker off the job to outfit them with an impinger or wet sampler for 15-minute increments during the workday resulting in lost time.

  • Single device captures both aerosol and vapor phase isocyanates.

  • 2-year shelf life.

  • No shipping of toluene reagents; Reduces risk of sample loss (leakage) and eliminates risk of contaminating other VOC samples (charcoal/tenax tubes).

  • Saves money over existing samplers. Sampling isocyanates reliably from as short as 15 minutes to 8 hours reduces the number of sampling devices required and provides true "Time Weighted Average" (TWA) sampling of the work environment.

  • Reliable results, no field desorption or analytical finish uncertainty.

  • After sampling, the ASSET EZ4-NCO device is stable with no special storage requirements; no immediate testing is required.