Tuning solvent-solute interactions enable visual colorimetric detection of nitro-aromatic explosives

Area of Science:

• Analytical Chemistry
• Organic Chemistry
• Environmental Science

Background:

• The Janowski reaction is crucial for detecting nitro-aromatic explosives visually.
• Solvent effects on this reaction are not well understood.
• Nitro-aromatic compounds pose significant safety and environmental risks.

Purpose of the Study:

• To investigate the solvent-dependent activity of the Janowski reaction.
• To develop a visual colorimetric assay for nitro-aromatic explosives.
• To understand the role of solvent properties in reaction efficiency.

Main Methods:

• Studied the Janowski reaction between 2,4-dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) with NaOH in four different solvents.
• Analyzed the solubility of reaction products (Meisenheimer complexes) in various solvents.
• Established a visual colorimetric assay based on observed color changes.

Main Results:

• Acetone, a solvent with high donor number and low polarity, effectively dissolved Meisenheimer complexes, enhancing the Janowski reaction.
• A visual colorimetric assay was developed, capable of detecting DNT and TNT.
• The assay demonstrated low detection limits (1.4 μM for DNT, 1.2 μM for TNT) and high selectivity, even in soil samples.

Conclusions:

• Solvent choice significantly impacts the Janowski reaction's efficiency for explosive detection.
• Acetone facilitates the reaction by solubilizing intermediates, enabling a simple, rapid, and visual detection method.
• This study provides insights into solvent effects and offers a practical assay for nitro-aromatic explosives.