SAMPLING AND ANALYSIS OF ISOCYANATES IN SPRAY-PAINTING OPERATIONS

Several methods were used for the sampling and analysis of airborne 1, 6-hexamethylene diisocyanate (HDI) and polyisocyanates during spray-pa inting operations. National Institute for Occupational Safety and Heal th (NIOSH) Method 5521 uses an impinger filled with 1-(2methoxyphenyl) piperazine in toluene for collection and derivatization, HPLC separati on, and simultaneous UV and EC detection. This method was compared dir ectly to Occupational Safety and Health Administration (OSHA) Method 4 2, which is based on sample collection on a fiber filter coated with 1 -(2-pyridyl)piperazine, HPLC separation, then UV detection. NIOSH Meth od 5521, modified so that polyisocyanate concentrations were determine d based on polyisocyanate standards, also was compared with NIOSH Meth od 0500, which is a gravimetric assay for total particulates. The resu lts for HDI monomer demonstrate that NIOSH Method 5521 appears to give higher results than those obtained using OSHA Method 42, especially w hen the total particulate concentration is high. Furthermore, field st udies show that polyisocyanate concentrations during spray paint opera tions may exceed a concentration of 1 mg/m(3), which is believed to be hazardous. Finally, preliminary results indicate that the true concen tration of polyisocyanate in air, in all cases but one, was within two rimes the theoretical concentration based on the total particulate ma ss.