Validated method for overcoming nitroaromatic thermolability in unmodified GC/MS using molecular isotope dilution...

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Mass Spectrometry

Background:

• Nitroaromatic explosives are common environmental contaminants.
• Accurate quantification of thermally labile explosives using GC/MS is challenging in standard laboratory settings.
• Existing methods often require specialized hardware or instrument modifications.

Purpose of the Study:

• To develop and validate a molecular isotope dilution mass spectrometry (m-IDMS) method for quantifying nitroaromatic explosives.
• To address challenges of thermal degradation and deuterium isotope effects in GC/MS analysis.
• To provide a validated method suitable for laboratories with standard instrumentation.

Main Methods:

• Developed and validated a molecular isotope dilution mass spectrometry (m-IDMS) method.
• Applied the method to quantify 2-nitrotoluene (2-NT), 2,6-dinitrotoluene (2,6-DNT), and 2,4,6-trinitrotoluene (2,4,6-TNT).
• Validated using laboratory spikes, certified reference materials (CRM), and proficiency tests.

Main Results:

• Achieved parts-per-billion limits of detection and linearity across three orders of magnitude.
• Demonstrated a relative mean uncertainty of 7.8% (95% CI) with no significant bias.
• m-IDMS improved sensitivity by 7x and uncertainty by 3x compared to calibration curves, accounting for a 6.46 isotope effect.

Conclusions:

• The validated m-IDMS method accurately quantifies thermolabile nitroaromatic explosives in environmental samples.
• The method is efficient, optimized, and requires no instrument modification, making it accessible for constrained labs.
• This approach overcomes limitations of standard GC/MS techniques for explosive analysis.