4,4’-Methylene Bisphenyl Isocyanate (MDI) by OSHA Method 47 on a Thermo Scientific ™ Acclaim™ PolarAdvantage II (PA2) Column

Significance of the Topic

The determination of 4,4’-Methylene Bisphenyl Isocyanate (MDI) in workplace air is essential due to its high toxicity and classification as a potential carcinogen. Ensuring accurate monitoring of MDI concentrations supports industrial hygiene programs and regulatory compliance in polyurethane manufacturing and related industries.

Goals and Overview of the Study

This work demonstrates the application of OSHA Method 47 for air sampling and analysis of MDI derivatives using high-performance liquid chromatography (HPLC). Key objectives include:

• Achieving reliable separation of MDI derivative from matrix interferences.
• Establishing sensitivity consistent with workplace exposure limits.
• Validating the robustness of the Acclaim PA2 column under prescribed conditions.

Methodology and Instrumentation

Samples of workplace air are collected on derivatization media and treated with 1-(2-pyridyl)piperazine (1,2-PP) following OSHA Method 47. The resulting MDI derivative is analyzed by reversed-phase HPLC.

Instrumentation Used

• Column: Thermo Scientific™ Acclaim™ PolarAdvantage II (PA2), 5 μm, 4.6 × 150 mm
• Pump: Thermo Scientific™ Dionex™ Summit P680 DGP
• Mobile Phase: 39.1% acetonitrile, 50% water, 10 mM ammonium acetate (pH 6.0–6.2)
• Flow Rate: 1.25 mL/min
• Column Temperature: 30 °C
• Injection Volume: 10 μL
• Detection: UV at 254 nm (optional 313 nm); optional fluorescence (ex. 240 nm, em. 370 nm)

Key Results and Discussion

The Acclaim PA2 column achieved baseline separation of the MDI derivative peak within 5 minutes. Chromatograms demonstrate:

• A reference derivative at 4.0 µg/mL with sharp peak shape.
• A low-level sample at 0.20 µg/mL showing adequate signal-to-noise ratio.
• A reagent blank confirming absence of interfering peaks from 1,2-PP.

Retention time repeatability was within acceptable margins, confirming column stability and method reproducibility.

Benefits and Practical Applications

This method offers:

• Rapid and reliable quantification of MDI for occupational exposure assessment.
• High selectivity for MDI derivative in complex sampling matrices.
• Compatibility with standard HPLC instrumentation in industry and research laboratories.

Future Trends and Applications

Advances may include coupling to mass spectrometric detection for enhanced sensitivity, miniaturized sampling devices for on-site monitoring, and expanded panels of diisocyanate derivatives for broader occupational health screening.

Conclusion

The application of OSHA Method 47 on the Thermo Scientific Acclaim PA2 column provides a fast, robust, and sensitive approach for monitoring MDI in workplace air. The validated separation and detection parameters support routine compliance testing and proactive exposure control.

References

• Thermo Fisher Scientific Inc. Application Note 25715, 2009.