Ionic Liquid-Based Microextraction Techniques in Analytical Chemistry

Ionic liquids have emerged as versatile solvents in microextraction, combining negligible vapour pressure, thermal stability and tunable polarity with green chemistry credentials. Their unique solvation properties facilitate the selective pre-concentration of organic and inorganic analytes across environmental, food and biological matrices. Techniques such as dispersive liquid–liquid microextraction (DLLME), single-drop microextraction (SDME) and solid-phase microextraction (SPME) exploit the high phase-transfer efficiency of ionic liquids to achieve large enrichment factors with minimal use of organic solvents. Advances include magnetic ionic liquids that enable rapid phase separation under an external field, thermo-responsive systems that trigger phase inversion with temperature changes, and ultrasound-assisted methods that reduce extraction times. Integrated with high-performance liquid chromatography or mass spectrometry, these approaches deliver low limits of detection, wide linear ranges and high reproducibility, supporting reliable monitoring of pollutants, pesticides, pharmaceuticals and biomolecules on a global scale.

Research from Nature Portfolio

A temperature-controlled, ultrasound-enhanced dispersive liquid–liquid microextraction method was developed for the determination of pyrethroid residues in herbal tea. An imidazolium-based ionic liquid served as extraction solvent, with ultrasonication and precise heating improving mass transfer and droplet dispersion. Optimisation of solvent volumes, pH and sonication time yielded linear responses over a broad concentration range, limits of detection in the low microgram-per-litre level and recoveries above 74%. The technique demonstrated rapid, reliable pretreatment and could be readily coupled to reversed-phase chromatography for routine quality control in botanical matrices.

Research from all publishers

A thermo-sensitive magnetic ionic liquid was integrated into an aqueous biphasic system for trace analysis of quinolone antibiotics in milk. Magnet-assisted phase separation and successive enrichment steps achieved high sensitivity without organic solvents, while recyclability of the ionic liquid enhanced sustainability. The method delivered satisfactory recoveries and limits of detection in complex dairy samples.

An ionic liquid-dispersive microextraction protocol was paired with liquid chromatography-electrospray ionisation mass spectrometry to quantify antifouling biocides in fresh and marine waters. Systematic optimisation of ionic liquid type, disperser solvent, pH and salt concentration led to enrichment factors exceeding 40, recoveries above 78% and detection limits as low as 0.01 µg L⁻¹. This demonstrates the adaptability of ionic liquid microextraction for trace monitoring in diverse aqueous environments.

Innovations in food analysis have employed ionic liquids in both DLLME and solid-phase microextraction to determine contaminants in food specimens. These studies combine structural designability of imidazolium and phosphonium cations with sorbent materials to extract pesticides and additives with high selectivity, low solvent consumption and rapid turnaround times, exemplifying the broad applicability of ionic liquid-based miniaturised extraction.

Ionic Liquid-Based Microextraction Techniques in Analytical Chemistry publication trend

The graph below shows the total number of articles in ionic liquid-based microextraction techniques in analytical chemistry across all publications each year (not limited to Nature Index journals).

Technical terms

Ionic liquid: A molten salt at or near room temperature, characterised by negligible vapour pressure, high thermal stability and tunable solvation properties.

Dispersive liquid–liquid microextraction (DLLME): A miniaturised technique where a small volume of extraction solvent is dispersed into an aqueous sample to form fine droplets, maximising contact area and extraction efficiency.

Solid-phase microextraction (SPME): A solvent-free technique that uses a coated fibre to adsorb analytes directly from a sample or its headspace, followed by thermal desorption into an analytical instrument.

Magnetic ionic liquid (MIL): An ionic liquid containing paramagnetic ions, enabling rapid phase separation under an external magnetic field without centrifugation.

Enrichment factor: The ratio of analyte concentration in the extraction phase to its initial concentration in the sample, indicating the pre-concentration capability of the microextraction technique.

References

1. Recent Advances in Applications of Ionic Liquids in Miniaturized Microextraction Techniques. Molecules (2018).
2. Determination of pyrethroid residues in herbal tea using temperature-controlled ionic liquid dispersive liquid-liquid microextraction by high performance liquid chromatography. Scientific Reports (2020).
3. Functionalized aqueous biphasic system coupled with HPLC for highly sensitive detection of quinolones in milk. LWT (2023).
4. Ionic Liquid-Dispersive Micro-Extraction and Detection by High Performance Liquid Chromatography–Mass Spectrometry for Antifouling Biocides in Water. Molecules (2023).
5. Ionic Liquid-Assisted DLLME and SPME for the Determination of Contaminants in Food Samples. Separations (2022).
6. Magnetic Ionic Liquids in Sample Preparation: Recent Advances and Future Trends. Separations (2021).
7. Ultrasound‐assisted temperature‐controlled ionic liquid dispersive liquid‐phase microextraction combined with reversed‐phase liquid chromatography for determination of organophosphorus pesticides in water samples. Electrophoresis (2016).