Method for determining airborne diisocyanates

A method has been developed for quantitatively determining 3 typical diisocyanates, viz. 2,4-toluylene diisocyanate (2,4-TDI), hexamethylene diisocyanate (HDI) and 4,4-diphenyl-methane diisocyanate (MDI). The technique relies on chemisorption onto a suitable carrier material contained in an absorption tube coated with 1-(2-pyridyl)piperazine (2-PP). Stable urea derivatives with high molar absorptivity are formed, desorbed from the carrier material, separated by means of highpressure liquid chromatography and identified. The limits of detection for a sample volume of 20 1 of air are 0.9g m^–3 for 2,4-TDI and HDI, and 0.6g m^–3 for MDI. The derivatives are stable at 4°C for longer than 30 days. The influence of atmospheric humidity and the interference of dibutylamine on the detection reaction were investigated for 2,4-TDI and HDI. The whole procedure is easy to perform, highly sensitive and very reproducible and is suitable for monitoring concentrations of 2,4-TDI, HDI and MDI.Dedicated to Prof. Dr. W. Fresenius on the occasion of his 75th birthday