Explosives Analysis Using Thin-Layer Chromatography-Quantum Cascade Laser Spectroscopy

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Chromatography

Background:

• High explosives (HEs) are significant anthropogenic contaminants.
• Accurate identification and quantification of HEs are crucial for safety and environmental monitoring.
• Existing analytical methods can be time-consuming or require specialized equipment.

Purpose of the Study:

• To present a new hyphenated technique combining thin-layer chromatography (TLC) and mid-infrared (MIR) laser spectroscopy.
• To demonstrate the method's utility for rapid screening, identification, and quantification of nitroaromatic and aliphatic nitro high explosives (HEs).
• To validate the technique by comparing results with established methods like attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy.

Main Methods:

• Developed a hyphenated technique integrating TLC for analyte separation with MIR laser spectroscopy for detection.
• Utilized 2,4,6-trinitrotoluene (TNT) as a model analyte for method validation.
• Employed multivariate analysis, including Partial Least Squares (PLS) regression and PLS-Discriminant Analysis (PLS-DA), for data evaluation, quantification, and classification.

Main Results:

• The TLC-MIR laser spectroscopy method provided rapid, robust, and reproducible analysis.
• Characteristic TNT spectral bands were identified at approximately 1350 cm⁻¹ and 1550 cm⁻¹.
• Achieved a detection limit of 84 ng and a quantification limit of 252 ng for TNT.
• Multivariate analysis effectively processed spectroscopic data for quantification and classification.

Conclusions:

• The new TLC-QCL technique offers a practical, low-cost, and fast approach for HE analysis.
• The method is sensitive and precise, with potential for portability as MIR laser technology advances.
• This technique is suitable for fieldwork and rapid screening of contaminants.