OSHA Method 41 for Diethylamine Using Acclaim Mixed-Mode HILIC-1

Significance of the Topic

Volatile amines such as diethylamine pose significant occupational health risks due to inhalation exposure in industrial settings. Reliable monitoring methods are essential to ensure worker safety, regulatory compliance, and process control in chemical manufacturing, environmental assessment, and quality assurance laboratories.

Study Objectives and Overview

This application note describes a streamlined adaptation of OSHA Method 41 for the determination of diethylamine. The goal is to improve chromatographic performance, reduce analysis time, and maintain compatibility with standard air-sampling derivatization procedures.

Methodology and Instrumentation

The derivatization reaction captures volatile amines from sampled air onto tubes containing 4-chloro-7-nitro-1,2,3-benzoxadiazole (NBD-chloride). After reaction with bicarbonate in tetrahydrofuran at 50 °C for two hours, the resulting NBD-derivative of diethylamine is separated by normal-phase liquid chromatography.

Instrumentation Used

• HPLC Column: Thermo Scientific Acclaim Mixed-Mode HILIC-1 (3 µm, 3 × 150 mm)
• LC System: Thermo Scientific Dionex UltiMate 3000
• Mobile Phase: Iso-octane:Isopropanol 80:20 (v/v)
• Flow Rate: 0.60 mL/min at 25 °C
• Injection Volume: 1 µL
• Detection: Diode Array Detector (spectra 200–600 nm), quantification at 465 nm

Main Results and Discussion

The NBD-diethylamine derivative eluted as a single, well-defined peak at approximately 3.2 minutes. Unreacted NBD-chloride and minor monoethylamine derivative elute separately at 2.3 and 4.4 minutes, respectively, without interfering with the target analyte. Compared with the conventional OSHA Method 41, this protocol delivers sharper peak shapes and reduces run time by up to 30%.

Benefits and Practical Applications

• Enhanced Throughput: Faster analysis supports high sample volumes in occupational monitoring programs.
• Improved Resolution: Clear separation from reagent and by-products minimizes false positives and quantification errors.
• Versatility: Mixed-mode HILIC column accommodates derivative polarity, enabling robust normal-phase separations.
• Compliance: Aligns with OSHA sampling standards while offering superior chromatographic performance.

Future Trends and Applications

Emerging developments may include ultra-high-performance liquid chromatography (UHPLC) formats for further time savings, coupling with mass spectrometry for trace‐level quantification, and adaptation to other volatile amine species. Integration into automated air-monitoring platforms could streamline field deployments and real-time exposure assessment.

Conclusion

The adapted method leveraging Acclaim Mixed-Mode HILIC-1 column chemistry provides an efficient, reliable approach for the determination of diethylamine in occupational air samples. Enhanced resolution, reduced analysis time, and compatibility with existing OSHA sampling protocols make this technique a valuable tool for industrial hygiene laboratories.