Liquid Phase Microextraction Techniques for Metal Ion Analysis

Liquid phase microextraction (LPME) encompasses a suite of sample preparation methodologies designed to isolate and concentrate trace metal ions from aqueous matrices using minimal volumes of extracting solvents. Key approaches include dispersive liquid–liquid microextraction (DLLME), vortex-assisted liquid phase microextraction and solvent bar microextraction. Green chemistry innovations have driven the adoption of deep eutectic solvents (DESs) and natural DESs as environmentally benign extractants, offering tunable polarity, low volatility and biodegradability. Integration of LPME with atomic absorption spectrometry, inductively coupled plasma optical emission or mass spectrometry, and laser-induced breakdown spectrometry enables multi-element detection at sub-ng mL⁻¹ levels. Recent advances focus on optimising extraction kinetics, tailoring ligand structures for selective metal-ion complexation and broadening applicability to complex matrices such as pharmaceuticals, environmental waters and foodstuffs. Collectively, these developments underscore the global significance of LPME techniques in environmental monitoring, food safety and pharmaceutical quality control.

Research from Nature Portfolio

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Research from all publishers

Recent studies have showcased the versatility of DES-based microextraction for pharmaceutical analysis, where a biodegradable menthol-decanoic acid DES achieved 12–85-fold improvements in limits of quantitation for Cd, Co, Hg, Ni, Pb and V in oral and parenteral drugs prior to ICP-OES detection. In environmental monitoring, dispersive liquid–liquid microextraction coupled with graphite furnace atomic absorption spectrometry employed a bespoke chelating agent and chlorobenzene–acetonitrile system to determine ultra-trace copper in water samples with detection limits down to 0.01 ng mL⁻¹ and an enrichment factor exceeding 100. Additionally, vortex-assisted liquid-phase microextraction utilising a hydrophobic l-menthol–ethylene glycol DES combined with GFAAS has been applied to lead, cadmium and mercury quantification in fish tissues, yielding detection limits of 0.05–0.10 µg kg⁻¹ and recoveries above 90%.

Liquid Phase Microextraction Techniques for Metal Ion Analysis publication trend

The graph below shows the total number of articles in liquid phase microextraction techniques for metal ion analysis across all publications each year (not limited to Nature Index journals).

Technical terms

Liquid phase microextraction (LPME): A group of techniques that use small volumes of liquid extractants to isolate and concentrate analytes from aqueous samples.

Dispersive liquid–liquid microextraction (DLLME): A rapid extraction method where an extraction solvent and a disperser solvent are simultaneously injected, forming a fine emulsion to enhance mass transfer.

Deep eutectic solvents (DESs): Mixtures of hydrogen bond donors and acceptors that form liquids with melting points lower than individual components, used as green extractants.

Graphite furnace atomic absorption spectrometry (GFAAS): A sensitive technique where a small sample is atomised in a heated graphite tube for trace metal detection.

Enrichment factor (EF): The ratio of analyte concentration in the extract to that in the original sample, indicating preconcentration efficiency.

References

1. Speciation of chromium by dispersive liquid–liquid microextraction followed by laser-induced breakdown spectrometry detection (DLLME–LIBS). Journal of Analytical Atomic Spectrometry (2015).
2. Dispersive liquid-liquid microextraction based on deep eutectic solvent for elemental impurities determination in oral and parenteral drugs by inductively coupled plasma optical emission spectrometry. Analytica Chimica Acta (2021).
3. New Potentials in the Extraction of Trace Metal Using Natural Deep Eutectic Solvents (NADES). Food Analytical Methods (2019).
4. Research Progress on Deep Eutectic Solvents and Recent Applications. Processes (2023).
5. Determination of Ultra-Trace Amounts of Copper in Environmental Water Samples by Dispersive Liquid-Liquid Microextraction Combined with Graphite Furnace Atomic Absorption Spectrometry. Separations (2023).
6. Solvent Bar Micro-Extraction of Heavy Metals from Natural Water Samples Using 3-Hydroxy-2-Naphthoate-Based Ionic Liquids. Molecules (2018).
7. An Environmental-friendly Procedure Based on Deep Eutectic Solvent for Extraction and Determination of Toxic Elements in Fish Species from Different Regions of Iraq. Journal of Food Protection (2023).