Analysis of Multiple NITC Derivatives of Volatile Amines Using Acclaim RSLC 120 C18

Significance of the topic

Volatile amines pose significant occupational and environmental health risks due to their toxicity and pungent odor. Accurate, sensitive monitoring of these compounds in workplace air is essential for ensuring compliance with safety regulations and protecting worker health. Traditional OSHA methods rely on normal-phase liquid chromatography, but modern reversed-phase techniques can deliver faster, more robust analyses.

Objectives and overview of the study

This study demonstrates a reversed-phase gradient LC method for the analysis of multiple volatile amine derivatives formed with 1-naphthyl isothiocyanate (NITC). The aim is to consolidate several OSHA methods into a single, efficient assay that improves peak shape, lowers detection limits, and accelerates total run time while maintaining broad analyte coverage.

Methodology

Airborne amines are first captured on sorbent tubes and derivatized with NITC to yield UV-active thiourea products. The derivatives are separated on a C18 column using a binary gradient of acetonitrile/methanol (2:1, v/v) and 10 mM formic acid in water. Detection is performed by diode array UV at 284 nm. The total analysis time is 5.5 minutes per injection.

Used instrumentation

• Column: Thermo Scientific™ Acclaim™ RSLC 120 C18, 2.1 × 100 mm, 2.2 µm
• LC system: Thermo Scientific™ Dionex™ UltiMate™ 3000
• Mobile phases: A–acetonitrile:methanol (2:1, v/v); B–10 mM formic acid in water
• Gradient: 45% A/55% B at 0 min to 96% A/4% B at 2.3 min, held to 5.5 min
• Flow rate: 0.425 mL/min; column temperature: 30 °C; injection volume: 1.0 µL
• Detector: Diode array UV (spectra 200–600 nm), monitoring at 284 nm

Main results and discussion

The method successfully resolved eleven peaks, including ten amine-NITC derivatives (ethanolamine, diethanolamine, methylethanolamine, methylamine, dimethylamine, ethylamine, diethylamine, ethylenediamine, diethylenetriamine, triethylenetetramine) and unreacted NITC. Peak shapes were sharp and symmetric, with baseline resolution achieved in under 6 minutes. Detection limits improved relative to normal-phase methods, enabling trace-level quantitation.

Benefits and practical applications

• Combines analyte lists from multiple OSHA methods into one assay
• Reduced analysis time and solvent consumption
• Enhanced sensitivity and reproducibility
• Streamlined workflow for occupational air monitoring and industrial hygiene laboratories

Future trends and potential applications

Advancements in ultra-high-pressure liquid chromatography could allow even faster separations. Coupling with mass spectrometry would expand the range of detectable amines and improve specificity. Automating sample derivatization and integrating on-site monitoring devices will further enhance workplace safety programs.

Conclusion

The reversed-phase RSLC C18 method for NITC-derivatized volatile amines offers a rapid, sensitive, and cost-effective alternative to conventional normal-phase techniques. It consolidates multiple target lists, improves analytical performance, and supports robust workplace exposure assessments.