Selective extraction of anionic and cationic dyes using tailored hydrophobic deep eutectic solvents

Area of Science:

• Analytical Chemistry
• Green Chemistry

Background:

• Deep eutectic solvents (DESs) offer tunable properties for separation science.
• Vortex-assisted liquid-liquid microextraction (LLME) is an efficient sample preparation technique.
• Selective separation of anionic and cationic dyes remains a challenge.

Purpose of the Study:

• To prepare and evaluate hydrophobic ionic and non-ionic DESs for vortex-assisted LLME.
• To investigate the selective extraction of anionic and cationic dyes using these DESs.
• To elucidate the extraction mechanism and assess the analytical performance.

Main Methods:

• Preparation of eight hydrophobic DESs (four ionic, four non-ionic).
• Application of DESs in vortex-assisted liquid-liquid microextraction (LLME).
• Analysis of anionic (tartrazine, amaranth) and cationic (phenosafranine, methylene blue) dyes.
• Mechanism investigation using FT-IR and 1H NMR spectroscopy.

Main Results:

• Ionic DESs selectively extracted anionic dyes, achieving 99.3% efficiency for tartrazine.
• Non-ionic DESs selectively extracted cationic dyes, reaching 99.9% partitioning for phenosafranine.
• Low limits of detection (0.06 μg mL⁻¹) and quantification (0.20 μg mL⁻¹) were achieved for tartrazine.
• Hydrogen bonding and electrostatic forces were identified as key extraction mechanisms.

Conclusions:

• Hydrophobic DESs demonstrate excellent selectivity for separating anionic and cationic dyes via LLME.
• The developed method offers high extraction efficiency, feasible operation, and selectivity.
• This approach presents an attractive alternative for dye separation and analysis.