Determination of methyl isocyanate in air by fluorimetry

Abstract

The fluorimetric determination of methyl isocyanate in air is described. Methyl isocyanate in air was absorbed with dimethyl sulfoxide and hydrolyzed to form methylamine. Methylamine was reacted with acetylacetone and formaldehyde in pH 5.6 HOAc–NaOAc buffer solution to form N-methyl-2,6-dimethyl-3,5-diacetyl- 1,4-dihydropyridine, which is a fluorescent substance. The measurement of relative fluorescence intensity was carried out at 474 nm with excitation at 404 nm. Effects of pH, heating time and foreign ions on the determination of methyl isocyanate were examined. The relationship between fluorescence intensity and concentration of methyl isocyanate was linear in the range 0.00–0.80 µg ml^–1. The linear regression equation was C = 0.001 I + 0.0092, with a linear regression correlation coefficient of 0.9994. The recovery was 98.3–104.5% and the relative standard deviation was 1.5%. The method is rapid, simple and highly sensitive, and can be used for the determination of methyl isocyanate in air. The results obtained agreed with those of an extraction-photometric method.