A Novel Analytical Scheme for Measuring Total Reactive Isocyanate Group Based on 1,8-Diaminonaphthalene

Details

• Personal Author:
  Bello D ; Ernst MK ; Nourian F ; Steinmetz MA ; Streicher, Robert P.
• Description:
  Research Purpose: Commercial isocyanate products are often complex mixtures of isocyanate species and analytical standards exist only for a few species. Quantitation of individual species is therefore difficult and labor intensive. Furthermore, current methods cannot measure unreacted isocyanate groups bound to non-chromatographable species, such as high molecular weight prepolymers or partial reaction products formed, for example, during spray foam applications of fast curing formulations. A new analytical method has been developed to overcome these issues. Relevance: The new method offers unique advantages for airborne and surface sampling of fast curing aerosols of aromatic isocyanates, and the only practical way for monitoring unreacted isocyanate groups attached to non-chromatographable species. Since the method involves only a single analyte and offers minimal sample workup with short analysis run time, it offers an economical and unambiguous technique for conducting total isocyanate group determinations. When combined with existing analytical techniques, unique insights can be gained on the chemical composition of complex samples and for studying the health relevance of exposure to such species. Methods: The analytical method utilizes 1,8-diaminonaphthalene (DAN) as the derivatizing reagent. Isocyanates are first converted into ureas during sample collection, analogous to established isocyanate methods. In a second post-collection step, the different DAN ureas are converted into a single analyte, perimidone. This step results from an intramolecular cyclization reaction in which the carbonyl (C=O) group that was a part of the original isocyanate group (-N=C=O), is effectively extracted to yield perimidone and the amine corresponding to the original isocyanate species. The amount of perimidone is proportional to the amount of total isocyanate contained in the sample. Air sampling is accomplished using impingers containing DAN in DMSO. A small aliquot of impinger solution (0.5 ml) is mixed with an equal volume of formic acid (a catalyst for cyclization). After 30 min, 10 uL acetone is added to the sample to consume excess DAN, followed by the addition of an internal standard, d6-perimidone (10 ng/mL). The sample is analyzed in 15 min runs by liquid chromatography - tandem mass spectrometry (LC-MS/MS) using a C18 column and mobile phase gradient. Perimidone is monitored via three transitions in the positive ion mode. Results: Laboratory validation of the DAN analytical scheme was performed via spikes of known amounts of several aromatic isocyanate bulk products in DAN/DMSO. The yield of perimidone averaged 98% (range 88-108%) of the theoretical isocyanate content determined via dibutylamine titration. The method is also highly reproducible and sensitive (limit of detection <100 pg/ mL). Conclusions: The DAN isocyanate chemistry has been developed into a working analytical method and its performance in laboratory testing has been satisfactory. An initial field study comparing DAN with several established methods has been completed and will be summarized. Field testing results showed that the total reactive isocyanate group (TRIG) values found with DAN were higher than those found with other TRIG determination methods, highlighting the ability of the DAN method to more fully assay isocyanate groups present. [Description provided by NIOSH]
• Subjects:
  Chemistry Chemistry, Analytic Isocyanates Laboratories Occupational Health Safety
• Keywords:
  Analytical Chemistry Analytical Methods Chemical Reactions Laboratory Testing Polyurethane Foams
• Publisher:
  Work Wellness and Disability Prevention Institute (WWDPI)
• Document Type:
  Text
• Genre:
  Abstract or Summary
• Place as Subject:
  Maryland ; Massachusetts ; Ohio ; OSHA Region 1 ; OSHA Region 3 ; OSHA Region 5
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DART - Division of Applied Research and Technology
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  80
• NIOSHTIC Number:
  nn:20054303
• Citation:
  Isocyanates & Health: Past, Present and Future, April 3-4, 2013, Potomac, Maryland. Vancouver, BC, Canada: Work Wellness and Disability Prevention Institute (WWDPI), 2013 Apr; :80
• Email:
  dhimiter_bello@uml.edu
• CAS Registry Number:
  1,8-Diaminonaphthalene (CAS RN 41,1,2,2-Tetrabromoethane (CAS RN 79-27-6))
• Federal Fiscal Year:
  2013
• Peer Reviewed:
  False
• Source Full Name:
  Isocyanates & Health: Past, Present and Future, April 3-4, 2013, Potomac, Maryland
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:329c509ded52e852f1d2a030d1ee89f90527a8aae4f1ac42d17f9253e83a7e6ea1360c69c7bccf68824ae6effddb34098bbd949936047a8cd601cb5ba688121b
• Download URL:
  https://stacks.cdc.gov/view/cdc/216895/cdc_216895_DS1.pdf
• File Type:
  [PDF - 705.20 KB ]