Simple Collection and 5-minute UHPLC Assay for 11 Isocyanates

By: Wayne K. Way, Reporter US Volume 32.1

Using ASSET EZ4-NCO Samplers and Titan C18 UHPLC Columns

Isocyanates are highly reactive, low molecular weight chemicals. They are widely used in the manufacture of flexible and rigid foams, fibers, coatings such as paints and varnishes, and elastomers. Spray-on polyurethane products containing isocyanates have been developed for a wide range of retail, commercial and industrial uses to protect cement, wood, fiberglass, steel and aluminum, including protective coatings for truck beds, trailers, boats, foundations and decks.

Isocyanates are powerful irritants to the mucous membranes of the eyes, and gastrointestinal and respiratory tracts. Isocyanates can also desensitize workers, making them subject to severe asthma attacks if they are exposed again. Preventing exposure to isocyanates is a critical step in eliminating the health hazard. Engineering controls such as closed systems and ventilation should be the principal method for minimizing isocyanate exposure in the workplace. Other controls, such as worker isolation and personal protective clothing and equipment may also be necessary. Monitoring exposure is equally critical in the health and well-being of workers.

With that in mind, a simple collection tube for personal monitoring and associated analytical assay has been developed to support the industrial hygiene market. The ASSET™ EZ4-NCO Dry Sampler (Figure 1) for isocyanates is safe for the worker to use for personal sampling because it requires no field addition of reagents, no field extraction and no special storage requirements. In addition, it is the only sampling device that achieves reliable low detection limits compared to existing commercially available devices. The ASSET EZ4-NCO sampling device is a unique dry sampler based on derivatization of isocyanate groups with di-n-butylamine (DBA). The sampler consists of a denuder and a filter, both impregnated with DBA. The extract is analyzed using LC-MS/MS offering the ultimate sensitivity and low detection limits not achievable with other methods.

The design offers several advantages over existing devices such as:

  • The ability to achieve low detection limits for both vapor and particulate phase isocyanates
  • Sampling time can range from 5 minutes to 8 hours
  • Fast derivatization reactions into stable derivatives
  • No special storage requirements; stable for 4 weeks after sampling
  • High capacity
  • No interferences
  • No breakthrough
  • No field extraction

Figure 1. ASSET EZ4-NCO Dry Sampler

 

Discussion
Figure 2 shows the chromatogram of a series of 11 common isocyanates. This isocyanate test mix is available as a standard, Cat. No. 40141-U. The gradient mobile phase employs LC-MS suitable solvents and buffers consisting of water, acetonitrile and formic acid. All peaks are well resolved, exhibiting baseline resolution. Peak shapes are symmetrical with minimal tailing. The 5 cm × 2.1 mm Titan™ UHPLC column. Cat. No. 577122-U, used in Figure 2 is a new offering from Supelco. Titan UHPLC columns are the outcome of the patent pending Ecoporous™ process, an economical route to UHPLC grade silica.

Figure 2. Chromatogram of 11 Common Isocyanates with MS Detection


CONDITIONS: column: Titan C18, 5 cm x 2.1 mm, 1.9 µm (577122-U); mobile phase: (A) 0.05% formic acid in 5:95 acetonitrile:water; (B) 0.05% formic acid in 95:5 acetonitrile:water; flow rate: 0.5 mL/min; pressure: 270 bar; column temp.: 30 °C; detector: MS, ESI (+), MRM; inj.: 2 µL; sample: isocyanates in acetonitrile, 0.06 µg/mL

 

Featured Products  
Description Cat. No.
Sample Collection Device  
ASSET EZ4-NCO Dry Sampler, 10 ea 5027-U
ASSET EZ4-NCO Dry Sampler, 50 ea 5028-U
Analytical Column  
Titan C18, 5 cm x 2.1 mm, 1.9 µm particles 577122-U
Analytical Standard  
DBA Isocyanate Standard Mix, 6 x 1 mL,
  Isocyanic acid-di-n-butylamine (ICA-DBA), 1 µg/mL
  Ethyl isocyanate-di-n-butylamine (EIC-DBA), 1 µg/mL
  Hexamethylene diisocyanate-2(di-n-butylamine) (HDI-2(DBA)), 1 µg/mL
  Isophorone isocyanate-2(di-n-butyl amine) isomer 1 (IPDI-2(DBA)), 1 µg/mL
  Isophorone isocyanate-2(di-n-butyl amine) isomer 2 (IPDI2-2(DBA)), 0.4 µg/mL
  4,4'-Methylenediphenyl diisocyanate-2(di-n-butylamine) (4,4'-MDI-2(DBA)), 1 µg/mL
  Methyl isocyanate-di-n-butylamine (MIC-DBA), 1 µg/mL
  Phenyl isocyanate-di-n-butylamine (PhI-DBA), 1 µg/mL
  Propyl isocyanate-di-n-butylamine (PIC-DBA), 1 µg/mL
  2,4-Toluene diisocyanate-di-n-butylamine (2,4-TDI-2(DBA)), 1 µg/mL
  2,6-Toluene diisocyanate-2(di-n-butylamine) (2,6-TDI-2(DBA)), 1 µg/mL
40141-U

View the complete line of isocyanate standards

Trademarks
Titan is a registered trademark of Sigma-Aldrich Co. LLC
ASSET is a trademark of Sigma-Aldrich Co. LLC

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