OSHA Method 34 for Dimethylamine Using Acclaim Mixed-Mode HILIC-1

Importance of the Topic

Volatile amines such as dimethylamine present significant occupational health risks due to their toxicity and potential for respiratory irritation. Monitoring these compounds in workplace air is essential for ensuring regulatory compliance and protecting worker health. Derivatization with fluorescent reagents enhances sensitivity and selectivity, enabling more accurate quantification at trace levels.

Objectives and Study Overview

This application note evaluates OSHA Method 34 adaptation for dimethylamine analysis using a mixed-mode HILIC column and NBD-chloride derivatization. The primary goals are to simplify the air-sampling workflow, accelerate chromatographic separation, and improve peak shape compared to traditional reversed-phase methods.

Methodology and Instrumentation

Derivatization and Sampling

• Air samples are drawn through a tube containing a reactive NBD-chloride trap.
• Volatile amines react with NBD-chloride under basic conditions (NaHCO3), forming a highly colored, fluorescent NBD-amine derivative.
• Reaction is carried out in THF at 50 °C for 2 hours.

Chromatographic Conditions

• Column: Thermo Scientific™ Acclaim™ Mixed-Mode HILIC-1, 3 µm, 3 × 150 mm.
• Mobile phase: Iso-octane:Isopropanol (50:50, v/v).
• Flow rate: 0.60 mL/min; column temperature: 25 °C; injection volume: 1 µL.

Detection

• Diode array detector scanning 200–600 nm; monitoring at 465 nm for the NBD derivative.

Main Results and Discussion

The NBD-dimethylamine derivative elutes at approximately 3 minutes, while unreacted NBD-chloride elutes at 1.8 minutes, eliminating coelution issues. Chromatograms demonstrate linear response for 8–41 µg/mL concentrations. Peak symmetry and resolution are significantly improved versus prior reversed-phase methods, reducing analysis time and reagent consumption.

Benefits and Practical Applications

This method offers the following advantages:

• Enhanced sensitivity due to fluorescent derivatization.
• Improved peak shape and baseline stability with mixed-mode HILIC.
• Faster throughput, supporting high-volume air monitoring programs.
• Compatibility with existing OSHA sampling protocols.

It is particularly suited for industrial hygiene laboratories and regulatory compliance testing.

Future Trends and Opportunities

Advances could include on-site portable derivatization and miniaturized HILIC systems for real-time monitoring. Additional applications may extend to other volatile amines and polar analytes in environmental and occupational settings. Integration with automated sampling platforms and high-resolution mass spectrometry could further improve detection limits and selectivity.

Conclusion

The adapted OSHA Method 34 using Acclaim Mixed-Mode HILIC-1 and NBD-chloride derivatization delivers rapid, sensitive, and reliable quantification of dimethylamine in air samples. Its enhanced chromatographic performance and adherence to established sampling approaches make it a robust solution for industrial hygiene and quality-control laboratories.

Reference

• Thermo Fisher Scientific. OSHA Method 34 for Dimethylamine Using Acclaim Mixed-Mode HILIC-1, Application Note PB20657_E, 2012.