ISO DIS 17735

Description / Abstract: This International Standard gives general guidance for the sampling and analysis of airborne organic isocyanates in workplace air.

This International Standard is appropriate for a wide range of organic compounds containing isocyanate groups, including monofunctional isocyanates (e.g. phenyl isocyanate), diisocyanate monomers (e.g. 1,6-hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), 4,4’-diphenylmethane diisocyanate (MDI), and isophorone diisocyanate (IPDI)), prepolymers (e.g. the biuret and isocyanurate of HDI), as well as chromatographable intermediate products formed during production or thermal breakdown of polyurethane.

In mixed systems of HDI and IPDI products, it is impossible to identify and quantify low levels of IPDI monomer using this International Standard, due to coelution of IPDI monomer with HDI-uretidinedione.

It is known that the method underestimates the oligomer in MDI-based products. Total isocyanate group (NCO) will be underestimated in MDI-based products by about 35% as compared to dibutylamine titration.

The method has been successfully modified to be used with LC-MS-MS for TDI monomer using an isocratic 70% acetonitrile/30% 10 mM ammonium formate mobile phase.

The useful range of the method, expressed in moles of isocyanate group per species per sample, is approximately 1 × 10⁻¹⁰ to 2 × 10⁻⁷. The instrumental detection limit for the monomers using both ultraviolet (UV) detection and fluorescent (FL) detection is about 2 ng monomer per sample. The useful limit of detection for the method using reagent impregnated filters is about 10-20 ng monomer per sample for both UV and FL detection. For a 15 l sample, this corresponds to 0.7-1.4 μg.m-3. For impinger samples, which require solid phase extraction, experience has shown that the useful limit of detection is about 30-80 ng monomer per sample.