A method for the determination of aromatic isocyanates in air in the presence of primary aromatic amines

Abstract

A method is described for the determination of aromatic isocyanates in air in the presence of primary aromatic amines. Samples of the test atmosphere are drawn simultaneously through two different absorbing solutions at 11 minute^–1 for 10 minutes. One sample is collected in a dimethylformamide solution of 1,6-diaminohexane and the other in a dimethylformamide-hydrochloric acid solution of 1,6-diaminohexane. The aromatic amine present, or produced, in each absorbing solution is diazotised and coupled with N-(1-naphthyl)ethylenediamine to form a coloured complex, the optical density of which is measured spectrophotometrically. The difference between the resulting optical densities gives a measure of the isocyanate content of the air. A complete analysis requires about 30 minutes.