Analytical problems encountered with NIOSH method 5521 for total isocyanates.
Am Ind Hyg Assoc J 1995 May; 56(5):474-479
The failure of the ratio criterion in the analysis of total isocyanates for a 1,6-hexamethylene-diisocyanate (822060) (HDI) based product was discussed. The analysis was made using the NIOSH Method 5521 to determine the concentration of total HDI in air. The air samples were collected during a survey at a facility involved in spray painting operations. Two coats of paint were being applied. The first was a white epoxy based primer and the top coat consisted of pigment and catalyst which were mixed in the spray gun. In the majority of the seven field samples collected and tested, a false negative response was obtained in the high performance liquid chromatography chromatograms. In some of the field blanks and in some of the field samples as well, an anomalous peak gave a false positive response. By using the complete ultraviolet absorption spectrum from a photodiode array (PDA) ultraviolet detector, it was possible to supplement the ratio criterion of Method 5521 and obtain successful identification of the two peaks. The author cautions that the addition of a PDA ultraviolet detector for confirmation of isocyanate oligomer is not recommended for routine use in the analysis of aromatic isocyanate products, as the aromatic rings are sources of ultraviolet activity in addition to that resulting from the derivatized isocyanate groups.
NIOSH-Author; Analytical-chemistry; Chemical-analysis; Analytical-methods; Chromatographic-analysis; Air-sampling-techniques; Spray-painting
American Industrial Hygiene Association Journal