A Comparison of Methods for the Determination of Isocyanates in Air

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Abstract
Isocyanates are in widespread use in certain industries such as in the manufacture of polyurethane products, paints and elastomers. The occupational exposure limit for isocyanates corresponds to 0.3 μg of isocyanate per sample using a 15 minute sampling time. Airborne isocyanates cause a variety of respiratory problems and workplace monitoring is therefore necessary. Two methods have recently been published by the Health and Safety Executive, one colorimetric and one HPLC using both electrochemical and UV detection. This study has compared these two methods using both field samples and laboratory generated standard atmospheres over a range of concentrations relevant to test the method at occupational exposure levels. The result of the field study showed that the colorimetric method was generally being used at its limit of sensitivity. Although potentially more sensitive, HPLC did show some interference with the field samples, thus limiting its sensitivity. The laboratory study showed good correlation between the two methods down to below half the TLV.