Ym. Roh et al., Development of a new approach for total isocyanate determination using thereagent 9-anthracenylmethyl 1-piperazinecarboxylate, ANALYST, 125(9), 2000, pp. 1691-1696
Diisocyanates and polyisocyanates are widely used in the manufacture of pol
yurethane materials and coatings. Exposure to airborne isocyanate species i
s known to cause respiratory disorders. Measurement of isocyanate exposure
levels has traditionally involved collection and derivatization of isocyana
te species in an air sample followed by reversed-phase HPLC analysis. HPLC
analysis of isocyanate samples is complicated for several reasons. Air samp
les may contain isocyanate species of very different reversed-phase retenti
on (e.g., monomeric and polymeric isocyanates) and some species may not eve
n be chromatographable. Also, pure analytical standards are available only
for monomeric isocyanates, so non-monomeric isocyanate species are typicall
y quantified based on the response of monomer standards, which assumes that
the non-monomeric species have the same response factor as the monomer. Fi
nally, the analysis of the raw chromatographic data containing many peaks i
s labor intensive. The method described here would circumvent many of the l
imitations of traditional methods. In this method, isocyanate species are d
erivatized with 9-anthracenylmethyl 1-piperazinecarboxylate (PAC) upon coll
ection. At this point, a portion of the sample can be analyzed for individu
al components of interest (such as monomers) and/or a portion can be treate
d with a reagent that converts all PAC derivatives to a single analyte. Qua
ntification of this analyte gives a measure of total isocyanate group. This
paper examines the reactivity of PAC, the separation of PAC derivatives fr
om excess PAC reagent, the conversion of PAC derivatives to a single analyt
e and the HPLC determination of this analyte and PAC derivatives of several
monomeric isocyanates.