Liquid-Liquid Microextraction Techniques for Mercury Speciation in Environmental Samples

Liquid-liquid microextraction (LLME) techniques have emerged as powerful tools for the speciation of mercury in various environmental matrices. By combining efficient preconcentration with minimal solvent consumption, LLME variants enable the separation of inorganic and organomercury species at trace levels. Dispersive liquid–liquid microextraction (DLLME) utilises a fine dispersion of extraction solvent in the sample to achieve rapid mass transfer, while emerging solvent systems such as natural deep eutectic solvents (NADES) and ionic liquids (ILs) offer enhanced selectivity and environmental compatibility. Solidified floating organic drop microextraction (SFODME) and cloud point–DLLME further refine phase separation, improving enrichment factors and lowering detection limits. Coupled with analytical techniques such as cold vapour atomic absorption spectrometry (CV-AAS), graphite furnace atomic absorption spectrometry (GFAAS) or liquid chromatography with UV–Vis detection, these methods facilitate robust quantification of Hg2+ and methylmercury across water, soil, biota and atmospheric particulate samples. Recent advances focus on green chemistry metrics, automation via microfluidic platforms and in situ sampling to ensure high sensitivity, reproducibility and traceability of results. The global significance of mercury speciation is underscored by its impact on ecosystem health, human exposure through the food chain and compliance with international monitoring initiatives.

Research from Nature Portfolio

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Research from all publishers

A study reported in 2024 demonstrated an ionic liquid-based solidified floating organic drop micro-extraction (IL-SFODME) method to preconcentrate trace mercury from diverse water samples without the need for chelating agents. Optimisation of IL type, pH, temperature and stirring conditions achieved an enrichment factor exceeding 170 and a detection limit of 0.12 µg L−1 by GFAAS, with relative standard deviations below 3 %. Validation on real and reference samples confirmed excellent accuracy and operational simplicity. In 2023, a natural deep eutectic solvent composed of decanoic acid and menthol was applied to DLLME for the simultaneous speciation of Hg2+ and organomercurials in tap, river and wastewater. The method achieved detection limits down to 0.9 µg L−1 for methylmercury, recoveries between 75–118 % and green preparative metrics in line with sustainability goals. A 2022 review of microextraction-based approaches highlighted recent innovations in sorptive and solvent-based extraction, emphasising the need for SI-traceable methodologies, in situ deployment and the integration of novel bio-based materials to address current analytical gaps across air, water, soil and biota compartments.

Liquid-Liquid Microextraction Techniques for Mercury Speciation in Environmental Samples publication trend

The graph below shows the total number of articles in liquid-liquid microextraction techniques for mercury speciation in environmental samples across all publications each year (not limited to Nature Index journals).

Technical terms

Liquid–liquid microextraction (LLME): A miniaturised liquid–liquid extraction technique using microlitre solvent volumes for preconcentration and separation of analytes.

Dispersive liquid–liquid microextraction (DLLME): A variant of LLME in which the extraction solvent is dispersed into the sample via a dispersive solvent or agitation to form fine droplets and enhance mass transfer.

Natural deep eutectic solvent (NADES): A biodegradable, non-toxic solvent formed from natural components such as organic acids and sugars, used to replace conventional organic solvents.

Ionic liquid (IL): A salt in the liquid state at ambient temperatures, with negligible volatility and tunable solvation properties for selective extraction.

Solidified floating organic drop microextraction (SFODME): A LLME approach where the extraction solvent solidifies at low temperature, facilitating easy phase separation and collection.

Cold vapour atomic absorption spectrometry (CV-AAS): An analytical detection method for mercury based on the generation of gaseous Hg0 and its absorption of ultraviolet light.

References

1. Natural deep eutectic solvent-based microextraction for mercury speciation in water samples. Analytical and Bioanalytical Chemistry (2023).
2. Recent applications and novel strategies for mercury determination in environmental samples using microextraction-based approaches: A review. Journal of Hazardous Materials (2022).
3. Determination of Mercury(II) on A Centrifugal Microfluidic Device Using Ionic Liquid Dispersive Liquid−Liquid Microextraction. Micromachines (2019).
4. Ionic Liquid-Based Solidified Floating Organic Drop Micro-Extraction Followed by Graphite Furnace Atomic Absorption Spectrometry for the Determination of Mercury in Water Samples. Applied Sciences (2024).