Spectrophotometric determination of aliphatic isocyanates in the occupational atmosphere. Part 1. Determination of total isocyanate concentration

Abstract

This paper describes a spectrophotometric method for use in the field for the determination of aliphatic isocyanates and their oligomers in air. The atmosphere being tested is drawn through a mixture of hydrochloric acid and dimethyl sulphoxide at a sampling rate of 2 l min^–1 for 10 min. Any isocyanates or oligomer present are hydrolysed to the corresponding amine. 1-Fluoro-2,4-dinitrobenzene is added and forms coloured derivatives with the amines. The absorbance of each derivative is measured at approximately 353 nm, and can be directly related to the amount of isocyanate. Concentrations down to 0.002 p.p.m. can be determined.