# Overview of NIOSH Method 5525 **and DAN Method for Total Isocyanate Determination**  Robert P. Streicher NIOSH

# Disclaimer Mention of company names and/or products does not constitute endorsement by the Centers for Disease Control and Prevention. The findings and conclusions in this presentation are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health.

# Common Diisocyanate Monomers **H 2**  **C N**  **N C**  **O C**  **O C**  **H 3**  **O C**  **H 3**  **N C**  **O N**  **C O**  **O M** **D I**  **2 ,**  **6 -** **T D**  **I C**  **H 3**  **N N**  **C O**  **C O**  **N N**  **C O**  **C O** 

**C H**  **3 N**  **C H**  **3 C**  **H 2**  **N C**  **O C**  **O H**  **3 C**  **C H**  **2 N**  **N C**  **O C**  **O H** **D I**  **I P**  **D I**  **H M** **D I**  **2 ,**  **4 -** **T D**  **I**

# Total **Isocyanate**
• All species with free (unreacted) isocyanate groups • Monomer (MDI) • Polymeric MDI (pMDI) – crude mixture of MDI monomer and higher oligomers • MDI prepolymer – product of polyol + excess of MDI or pMDI • Partial reaction products during polyurethane production

## Importance of Measurement of Total **Isocyanate versus Monomer only** • Recognition that not only monomeric isocyanates present exposure hazards • Measurement of monomeric isocyanate may Measurement monomeric isocyanate not be a good surrogate for total isocyanate exposure • Monomer may represent small percentage of isocyanate product (e.g. prepolymers)

# Air Sampling Recommendations

**for MDI/pMDI** • Impingers

– Used for fast- cure particles > 2 μm

- Typical for spray of MDI/pMDI

- Acceptable for vapor collection • Reagent- coated Filters

– Preferred for vapor collection

– Used for:

- All particles < 2 μm

- Slow - cure particles > 2 μm

– Extract filters in the field

– High-boiling solvent on filters (?)

# NIOSH Method 5525 **– MAP Derivatizing**  **Reagent**
N H N C H 2 N 1 - (9 - A nt hr a c e nyl m et hy l ) p i p e ra zi ne ( MA P )

# Advantages **of MAP** • Derivatization - reacts rapidly with isocyanates • Chromatography - pH gradient • Indentification - sensitive and selective by UV/FL • Quantification - universal UV response factor

# Polymeric MDI Bulk

# How the DAN Method Works

**N H**  **2 N**  **H 2**  **N N**  **H 2**  **H +**  **a c**  **e t** **i c**  **D A** **N R**  **N C**  **O C**  **O N**  **H R** 

**N H**  **H N**  **+ R**  **N H**  **2 a**  **c e** **t i**  **c**

**a c** **i d**  **D A** **N 1**  **H -**  **P e**  **r i** **m i**  **d i** **n -**  **2 (** **3 H** **) -** **o n**  **e C**  **O**

# Evaluation **of DAN Chemistry**
• Works well for aromatic isocyanate systems (MDI and TDI) • Problems with quantitative reaction in aliphatic systems (HDI)

# Goals of Analytical Method **Development for Perimidone** • High accuracy • Covers a broad concentration range • Covers a broad range of isocyanate species • Simple and inexpensive: interpretation- free

# Mass **Spectrum of Perimidone 184**  **166** Abundance

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 **166**

155 139 92 83 128

101 63 113 51 75 m/z Abundance

# Perimidone **and Deuterated**  **Perimidone**

N H C H N O N H C H N O N H H N H

H H H H H D D D D D D **MW = 184**  **MW = 190** 

# Total Ion Current Chromatogram of 2.5 ug/mL Perimidone + 30 ug/mL Deuterated Perimidone

3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.00 14.00 Ti me → Abundance

# Mass Spectrum of Sample Containing Perimidone and Deuterated Perimidone **190**

155 160 165 170 175 180 185 190 195 200 Abundance **184 172**  **166** 161 m/z 187

# Acknowledgments

Kathy Ernst, Fariba Nourian (NIOSH) Dr. Dhimiter Bello (U. of Mass. Lowell)

# Uncertainties in Exposure **Assessment and Research Gaps**  **Related to use of MDI Foam Insulation** 

## How Important is Dermal Exposure in

**Respiratory Sensitization?**
• Animal studies are definitive • Observed respiratory sensitization in environments with little or no inhalation exposure • Bello et al., Skin Exposure to Isocyanates: Reasons for Concern , Environ. Health Perspectives 115: 328 - 335 (2007).

# Research Questions in Application **of MDI -** **based Foam Insulation**  • What is the lifetime of isocyanates on the surface of foam? • What is the exposure hazard (inhalation and/or dermal) from cutting newly hardened foam insulation? • How important are isocyanate groups chemically bound (as opposed to adsorbed) to foam surfaces of dust? • How can chemically-bound isocyanate groups be measured?

# Thermal Breakdown of **Polyurethane Foam can present an Exposure Hazard**  • Thermal breakdown of polyurethane produces various isocyanate species including monomer, aminoisocyanates, low molecular weight isocyanates. • May occur when manipulating cured foam or working on adjacent fixtures. • Isocyanate exposure hazard is not recognized by worker or homeowner