Simultaneous Preconcentration Research Articles

Advancements in Multiple‐Step On‐Line Preconcentration Techniques for Enhanced Sensitivity in Capillary Electrophoresis

ABSTRACTMultiple‐step on‐line preconcentration, a combination of at least two stacking techniques has been developed to increase the sensitivity in capillary electrophoresis (CE) for analytes in various samples. It is usually conducted sequentially, or in some cases, synergistically, where different stacking modes occur simultaneously. Multiple‐step techniques allow simultaneous preconcentration and separation of various kinds of analytes in different complex samples in a single CE run. This review aims to provide recent advances in multiple‐step on‐line preconcentration techniques in CE. We critically review technical papers published for the last 7 years up until July 2024, subsequently organized according to the combination of the main stacking techniques, that is, field amplification, large volume sample stacking, transient isotachophoresis, micelle to solvent or micelle to cyclodextrin stacking, and others. The procedures, fundamental mechanism, analytical figures of merits achieved, and their feasibility for complicated sample matrices are reviewed.

Green dispersive liquid–liquid microextraction of copper and nickel using a dual-function hydrophobic natural deep eutectic solvent for the analysis of water samples

An environmentally friendly and simple dispersive liquid–liquid microextraction method based on a hydrophobic natural deep eutectic solvent (NADES) was developed for the simultaneous preconcentration of Cu and Ni from water samples. The NADES composed of a 1:1 molar ratio of menthol and decanoic acid, presents hydrophobic characteristics and allows to simultaneously extract both analytes avoiding the addition of ligands or emulsifier agents. The extraction was performed in 1.0 min using 0.500 mL of NADES and a sample volume up to 25.0 mL in 0.5 M ammonium chloride-ammonia buffer solution at pH 8.2. The content of Ni and Cu in the NADES phase was determined using Flame Atomic Absorption Spectroscopy. Under optimal conditions, limits of detection of 1.9 µg L−1 for Cu and 4.6 µg L−1 for Ni were obtained, with precision (expressed as RSD% value) better than 5 % for both metals (n = 3). The method was applied to extract and determine Cu and Ni in water samples with different characteristics: tap water, bottled water, river water, dam water, and seawater. The recoveries for spiked water samples ranged between 97 and 110 % for Cu and 92–98 % for Ni, demonstrating the suitability of the method. The environmental impact of the method was assessed using the AGREE, AGREEprep, and ChlorTox metric tools, resulting in scores of 0.58, 0.61, and 0.48 g, respectively.

Simultaneous preconcentration and quantification of ultra-trace tin and lead species in seawater by online SPE coupled with HPLC-ICP-MS

BackgroundTin and lead contamination is a global threat to marine ecosystems considering their species-specific toxicity, bioavailability and mobility. Hence simultaneous measurement of multiple tin and lead compounds at μg L−1 to pg L−1 levels in environmental water is always an indispensable but challengeable task. High performance liquid chromatography coupled with inductively coupled plasma mass spectrometry (HPLC-ICP-MS) is one of the most widely used choices for this purpose because of good sensitivity, strong separation power and good compatibility. Previous HPLC-ICP-MS methods based on a single elemental speciation strategy are low-efficiency and sensitivity-insufficient for a large set of unstable samples and interaction of multiple metal(loid)s down to ng L−1 levels. ResultsIn this study, we developed a sensitive, efficient and environment-friendly analytical method for accurate quantification of inorganic and organic species of tin and lead simultaneously based on HPLC-ICP-MS with online integration of solid phase extraction (SPE). By using graphene oxide modified silica conditioned with 1 mM benzoic acid to enrich tin and lead species from 10 mL sample, detection limits were improved to 2–8 pg per liter due to satisfactory enrichment factors (522−2848 folds). The SPE-HPLC-ICP-MS method was applicable to quantification of ultra-trace tin and lead species at pg L−1 levels in uncontaminated seawater. Tributyltin was the only tin species detected at subnanograms per liter levels while Pb(II) was the only lead species detected at several nanograms per liter in thirteen coastal seawater samples collected in Hangzhou Bay, indicating light contamination of tin and lead. SignificanceOverall, the proposed SPE-HPLC-ICP-MS method is highly sensitive, efficient and environment-friendly that are fairly suitable to routine speciation analysis of tin and lead in environmental, food, and biological samples.

Development of a dispersive liquid–liquid microextraction procedure based on a natural deep eutectic solvent for ligand-less preconcentration and determination of heavy metals from water and food samples

In the current study, a ligand-less dispersive liquid–liquid microextraction technique assisted ultrasound and vortex equipment (DLLME-A-US-V) procedure was used for the simultaneous preconcentration and extraction of heavy metal ions. The proposed method was done by a natural hydrophobic deep eutectic solvent for the extraction of arsenic, cadmium, lead, and mercury ions without a complexing agent. The natural deep eutectic solvent was prepared from l-menthol (M) and salicylic acid (SA). The precursor of deep eutectic solvents strongly affects the extraction of metal ions. Among the studied solvents, hydrophobic deep eutectic solvents showed the highest extraction recovery. Under optimal experimental conditions, the method linearity, limits of detection (LOD), limits of quantification (LOQ), relative standard deviations (RSD %), enrichment factors (EF), and extraction recovery (% ER) were equal to 0.005–14 µg/L, 0.0043–0.0088 µg/L, 0.0143–0.0294 µg/L, 1.66–2.83 %, 112–120, and 90–96 %, respectively. The obtained coefficients of determination (r2) were also higher than 0.991. This method was successfully applied to determine some heavy metals in food samples in the ultra-trace range with the recovery values of real samples being 93–108 %.

A flow-batch lab-in-syringe foam microextraction platform for the simultaneous preconcentration and in situ membraneless gas-liquid separation of mercury prior to cold vapor atomic absorption spectrometry

Herein, the proof-of-concept of a novel lab-in-syringe (LIS) foam microextraction platform is presented as a front-end to cold vapor atomic absorption spectrometry (CVAAS) for the simultaneous preconcentration and membraneless gas-liquid separation (GLS) of inorganic mercury in biological samples. The proposed method is based on the on-line formation of the ammonium pyrrolidine dithiocarbamate complex with mercury that was retained in the pores of polyurethane foam immobilized on the piston of the LIS system. Metal complex elution and in situ mercury vapor generation are accomplished inside the microsyringe in a flow-batch format, while the separation of vapor species is achieved via the membraneless GLS found at the top of the syringe’s barrel. Under optimized operation conditions, for 90 s preconcentration time, the limit of detection was 0.02 μg L−1 and the repeatability (RSD) was 3.8% (at the 0.5 μg L−1 concentration level), within a working range extending up to 4.0 μg L−1. The practicality of the novel manifold was demonstrated using the Blue Applicability Grade Index, while the accuracy of the method was evaluated using certified reference materials and spiked samples.

Simultaneous Preconcentration and Determination of Nile Blue A and Rhodamine B in Aqueous Samples by the Cloud Point Extraction Coupled with the Solution Scanometric Method

Simultaneous Preconcentration and Determination of Nile Blue A and Rhodamine B in Aqueous Samples by the Cloud Point Extraction Coupled with the Solution Scanometric Method

Metal-organic framework-based high-performance column chip for micro gas chromatography: hybrid function for simultaneous preconcentration and separation of volatile organic compounds.

Numerous attempts have been made to replace commercial bulky gas chromatography (GC) systems with compact GC systems for monitoring volatile organic compounds in indoor air. However, recently developed compact GC systems are still too bulky in terms of user convenience, portability, and on-site analysis. Hence, an advanced miniaturization of compact GC systems is needed. Importantly, the small and high-performance gas pretreatment chip devices should be developed for compact GC systems. This paper reports the development of a metal-organic framework (MOF)-coated hybrid micro gas chromatography column chip (hybrid GC chip) capable of preconcentration and separation on harmful volatile organic compounds at low-concentration in one single chip device. The hybrid GC chip, 2 cm × 2 cm in size, was fabricated using a microelectromechanical systems process. The synthesized MOF-5 particles were coated on the inner wall of the fabricated hybrid GC chip and acted as an adsorbent and a stationary phase. The developed hybrid GC chip afforded high preconcentration factors with 1033-1237 and high separation resolutions with 3.8-13.3. The developed column showed good performance as a gas preconcentrator and separation column, and is the first device to perform both roles in one single chip device.

Simultaneous Preconcentration of Fast Green FCF and Rhodamine B Using Deep Eutectic Solvent and Determination via High-Performance Thin Layer Chromatography

The aim of the current investigation is the development of a green, quick, easy, and accurate method for simultaneous preconcentration of fast green FCF (FG) and rhodamine B (Rh B) using a deep eutectic solvent (DES). Then, the high-performance thin layer chromatography (HPTLC) technique was used for the determination of analytes. Decanoic acid and tetrabutylammonium bromide were chosen as the components of DES. HPTLC analysis was performed on an aluminum plate silica gel 60 F254. Methanol-ammonia and ethyl acetate were selected as the mobile phase. Scanning of the plates was accomplished by scanner 3. Effective parameters on the preconcentration process such as concentration of salt, volume of DES, stirrer time, and pH were investigated via central composite design (CCD). Data validation demonstrated good repeatability. The limit of detection for FG and Rh B was obtained as 0.08 and 0.01 µg·mL−1, respectively. The enrichment factor for FG and Rh B was achieved as 7.43 and 10.77, respectively. The linear ranges for FG and Rh B were acquired as 0.10–1.20 and 0.05–1.20 µg·mL−1, respectively. The preconcentration factor for both analytes was 21.66. Finally, the proposed method was successfully used for the quantitation of FG and Rh B in pastille and lipstick.

Thiol-Functionalized MIL-100(Fe)/Device for the Removal of Heavy Metals in Water.

The preparation of a functional device based on a functionalized MIL-100(Fe) metal-organic framework for the solid-phase extraction of heavy metals is reported. By a simple and easy straightforward grafting procedure, a thiol-functionalized MIL-100(Fe) material (MIL-100(Fe)-SH) with a S/Fe ratio of 0.80 and a surface area of 840 m2 g-1 was obtained. MIL-100(Fe)-SH exhibited a higher Hg(II) extraction (96 ± 5%) than that of MIL-100(Fe) (78 ± 4%) due to the interaction between thiol groups and Hg(II) ions. For practical applications, the obtained MIL-100(Fe)-SH was integrated by a simple method to a 3D printed support based on a matrix of interconnected cubes using poly(vinylidene fluoride) as binder, obtaining a functional device that simultaneously acts as stirrer and sorbent. The developed device showed high efficiency for the removal of Hg(II), good reusability, and excellent performance for the simultaneous preconcentration and further detection and quantification of Hg(II), Pb(II), and As(V) in tap, well, and lake water samples.

Ultrasound-enhanced dispersive solid phase extraction of Cd (II), Co (II), and Ni (II) using magnetic Pinus pinea

A new ultrasound assisted dispersive solid phase extraction (DSPE) technique has been combined with flame atomic absorption spectrometry (FAAS) to enable the simultaneous preconcentration, determination and removal of cadmium, cobalt and nickel ions from aqueous samples. In this procedure, a magnetic Pinus pinea bio-adsorbent was synthesized and used as bio-adsorbent. The parameters such as solution pH, ultrasound time, analyte concentration and interfering ions were successfully optimized. All three metal ions were extracted within a mere 120 s at pH 6 and the extraction recovery values of the all three analytes were quantitative (˃95%) under the optimal conditions. The adsorption processes of the metal ions were analyzed and adsorption of the metal ions were identified by Energy Dispersive X-Ray Mapping technique. A certified reference material was analyzed for the accuracy of the method. Finally, the developed method was applied for preconcentration and determination of the analytes in real water samples including natural spring water, natural mineral water and factory process water.

Simultaneous preconcentration of 9Be and cosmogenic 10Be for determination of the 10Be/9Be ratio in (coastal) seawater

AbstractBeryllium isotopes have emerged as a quantitative tracer of continental weathering, but accurate and precise determination of the cosmogenic 10Be and stable 9Be in seawater is challenging, because seawater contains high concentrations of matrix elements but extremely low concentrations of 9Be and 10Be. In this study, we develop a new, time‐efficient procedure for the simultaneous preconcentration of 9Be and 10Be from (coastal) seawater based on the iron co‐precipitation method. The concentrations of 9Be, 10Be, and the resulting 10Be/9Be ratio for Changjiang Estuary water derived from the new procedure agree well with those obtained from the conventional procedure requiring separate preconcentration for 9Be and 10Be determinations. By avoiding the separate preconcentration, our newly developed procedure contributes toward more time‐efficient handling of samples, less sample cross‐contamination, and a more reliable 10Be/9Be ratio. Prior to this, we validated the iron co‐precipitation method using artificial seawater and natural water samples from the Amazon Estuary regarding: (1) the “matrix effect” for Be analysis, (2) its extraction efficiency for pg g−1 levels Be in the presence and absence of organic matter, and (3) the data comparability with another preconcentration method. We calculated that for the determination of 9Be and 10Be in most open ocean seawater with typical 10Be concentrations of > 500 atoms g−1, good precisions (< 5%) can be achieved using less than 3 liters of seawater compared to more than 20 liters routinely used previously. Even for coastal seawater with extremely low 10Be concentration (e.g., 100 atoms g−1), we estimate a maximum amount of 10 liters to be adequate.

Surface engineered functional biomaterials for hazardous pollutants removal from aqueous environment

The issue of water contamination by heavy metal ions as highly persistent pollutants with harmful influence primarily on biological systems, even in trace levels, has become a great environmental concern globally. Therefore, there is a need for the use of highly sensitive techniques or preconcentration methods for the removal of heavy metal ions at trace levels. Thus, this research investigates a novel approach by examining the possibility of using pomegranate (Punica granatum) peel layered material for the simultaneous preconcentration of seven heavy metal ions; Cd(II), Co(II), Cr(III), Cu(II), Mn(II), Ni(II) and Pb(II) from aqueous solution and three river water samples. The quantification of the heavy metals was performed by the means of FAAS technique. The characterization of biomaterial was performed by SEM/EDS, FTIR analysis and pHpzc determination before and after the remediation process. The reusability study as well as the influence of interfering ions (Ca, K, Mg, Na and Zn) were evaluated. The conditions of preconcentration by the column method included the optimization of solution pH (5), flow rate (1.5 mL/min), a dose of biosorbent (200 mg), type of the eluent (1 mol/L HNO3), sample volume (100 mL) and sorbent fraction (<0.25 mm). The biosorbent capacity ranged from 4.45 to 57.70 μmol/g for the investigated heavy metals. The practical relevance of this study is further extended by novel data regarding adsorbent cost analysis (17.49 $/mol). The Punica granatum sorbent represents a highly effective and economical biosorbent for the preconcentration of heavy metal ions for possible application in industrial sectors.

Modification of Magnetic Graphene Oxide by an Earth-Friendly Deep Eutectic Solvent to Preconcentrate Ultratrac Amounts of Pb(II) and Cd(II) in Legume Samples

A novel magnetic solid-phase extraction adsorbent using deep eutectic solvent-coated magnetic graphene oxide (EgLiCl-mGO) was proposed for simultaneous preconcentration of Pb(II) and Cd(II). The nanocomposite was characterized by Fourier Transform Infrared Spectroscopy, X-ray diffractometry, and alternative gradient force magnetometer. Parameters that could affect the preconcentration recoveries of the target ions were investigated via the one-factor-at-a-time method. The optimum conditions are pH of 4 ± 0.5, EgLiCl-mGO amount of 1.0 × 10−2 g, adsorption time of 5 min, eluent of HNO3 (1 mL, 2 mol L−1), and desorption time of one minute. The swelling property of the adsorbent versus pH was studied. The linearity of the dynamic range for Pb(II) (5.0 × 10−6–4.0 × 10−4 g L−1) and Cd(II) (5.0 × 10−6–15 × 10−5 g L−1) was recorded. The limits of detection were Pb(II): 1.2 × 10−6 g L−1 and Cd(II): 47 × 10−8 g L−1. The preconcentration factor of 50 was calculated for both ions and the relative standard deviations were 1.27% for Pb(II) and 0.94% for Cd(II). Reusability, effect of interference ions, selectivity, isotherm adsorption, kinetic adsorption, and thermodynamic adsorption were established. The adsorbent was successful at preconcentrating the ions in legumes.

Simultaneous Preconcentration and Determination of Cu(II), Ni(II), and Co(II) in Food and Environmental Samples by the Application of Chelate Adsorption on Amberlite XAD-1180

Simultaneous Preconcentration and Determination of Cu(II), Ni(II), and Co(II) in Food and Environmental Samples by the Application of Chelate Adsorption on Amberlite XAD-1180

Application of oxidized multi-walled carbon nanotubes and zeolite nanoparticles for simultaneous preconcentration of codeine and tramadol in saliva prior to HPLC determination

In this work, a dispersive micro-solid phase extraction technique along with high-performance liquid chromatography-UV detection was developed for simultaneous preconcentraion and determination of trace levels of codeine and tramadol in human saliva. This method is based on the adsorption of codeine and tramadol on a mixture of oxidized multi-walled carbon nanotubes and zeolite Y nanoparticles with 1:1 ratio as an efficient nanosorbent. Various analytical parameters influencing the adsorption step including the amount of adsorbent, the pH of the sample solution, the temperature, the stirring rate, the contact time of the sample solution, and the adsorption capacity were investigated. Based on the results, 10 mg adsorbent, sample solutions with pH = 7.6, temperature of 25 °C, stirring rate 750 rpm and contact time 15 min, in the adsorption step shows the best results for both drugs. Then the effective parameters on the analyte desorption stage such as the type of desorption solution, pH of the desorption solution, desorption time and desorption volume were investigated. Studies have shown that water/methanol (50:50 v/v) as desorption solution, pH = 2.0, desorption time of 5 min and desorption volume of 2 ml gives the best results.Chromatographic separation was performed on a RP-Shim-pack CLC-ODS-C18 column (250 mm × 4.6 mm, 5 µm) with isocratic mode. The mobile phase contained of acetonitrile:phosphate buffer (18:82, v/v) at pH = 4.5 and the flow rate was 1 ml.min−1. The wavelength of UV detector was adjusted at 210 nm and 198 nm for codeine and tramadol, respectively.Under optimum conditions, the extraction efficiencies of 98.5% and 99.2% were achieved for codeine and tramadol respectively. Enrichment factor of 13, detection limit of 0.3 μg L−1, relative standard deviation of 4.07 for codeine; and an enrichment factor of 15, a detection limit of 0.15 μg L−1, and standard deviation of 2.06 for tramadol were calculated. The linear range of the procedure for each drug was 1.0 to 1000 μg L−1. This method was successfully applied for the analysis of codeine and tramadol in saliva samples.

Ultrasound-assisted dispersive liquid–liquid microextraction combined with ion mobility spectrometry for the simultaneous preconcentration and determination of dimethoate and chlorpyrifos in fruit, vegetable, and water samples

A rapid, sensitive, and reliable method based on ultrasound- assisted dispersive liquid–liquid microextraction followed by ion mobility spectrometry analysis (UA-DLLME-IMS) is reported for the preconcentration and determination of chlorpyrifos and dimethoate in food and water. The sample pH, volume of dichloromethane (extraction solvent), sonication, and centrifuge time, salt effect and sample volume were individually optimized. Under the optimum conditions, the calibration curves were linear from 5 to 200 µg L−1 and 3 to 280 µg L−1. Limits of detection (LOD) of 1.3 and 0.8 µg L−1 were obtained for chlorpyrifos and dimethoate, respectively. The relative standard deviations at 20 μg L−1 (n = 5) for intra- and inter-day precision were 2.8% and 3.9% for chlorpyrifos and 4.1% and 4.6% for dimethoate, respectively. The procedure was validated for the determination of chlorpyrifos and dimethoate in food and water samples.

Simultaneous preconcentration and determination of trace metals in edible plants and water samples by a novel solvent bar microextraction using a meltblown layer of facemask as the extractant phase holder combined with FAAS

A new microextraction method as a facile, efficient, and safe intermediate sample preparation procedure was developed for simultaneous extraction and preconcentration of nickel (II), cobalt (II), and lead (II) in some vegetables and water samples. The new method uses a novel deep eutectic solvent as an extractant on the surface of a meltblown layer of a facemask with an iron wire inside of it. 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) was used as a chelating reagent. The concentrations of the enriched ions were measured using a flame atomic absorption spectrophotometer (FAAS). The introduced method underwent significant parameter optimization, which may influence the extraction process efficiency. Under the best situations, the calibration curve of the method showed excellent linearity over the concentration range 2–150 μg L−1, 3–150 μg L−1, and 7–500 μg L−1 have satisfactory coefficients of determination (R2 ≥ 0.998) for nickel (II), cobalt (II), and lead (II), respectively. Detection limits were within 0.61 – 2.30 μg L−1, and the relative standard deviation values were fewer than 2.6 % (n = 10). Experimental results indicated that the presented method has a high ability to cleanly and enrich metal ions in several samples, including natural water, dill, coriander, and spinach leaves, with limited solvent consumption and low operating costs.

Simultaneous determination and extraction of illegal dyes Sudan orange G and Sudan red 7B using ultrasonic assisted dispersive liquid–liquid microextraction based on deep eutectic solvent followed by derivative UV-VIS spectrophotometry

ABSTRACT An ultrasonic-assisted dispersive liquid–liquid microextraction based on deep eutectic solvent was utilised for simultaneous preconcentration and determination of illegal dyes Sudan orange G (SOG) and Sudan red 7B (SR7B) using second derivative ultraviolet spectrophotometry. Under optimised conditions, the limit of detection (0.014 and 0.011 μg mL−1) and linear dynamic range (0.036–0.900 and 0.030–1.000 μg mL−1) with high determination coefficient of 0.9916 and 0.9937 were obtained for SOG and SR7B, respectively. The relative standard deviations of method (n = 3) for intra- and inter-day were obtained as 3.5% and 10.5% for SOG and 5.0% and 9.0% for SR7B. The preconcentration factor for both dyes was calculated as 75 for all experiments. The applicability of the proposed method was investigated in different real samples, including in chilli powder, lipstick, river water and also in well water. A relative recovery percentage of 88–114% was obtained for these samples. Effect of interferences for the model solutions was also examined wherein satisfactory results confirm reasonable selectivity of the proposed method.

Rapid determination of multiclass antibiotics and their metabolites in milk using ionic liquid-modified magnetic chitosan nanoparticles followed by UPLC-MS/MS

This research introduced a rapid and efficient method for simultaneous pre-concentration and determination of twenty-two antibiotics and their metabolites in milk samples using functional imidazole-based ionic liquid-modified magnetic chitosan nanoparticles followed by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Different techniques characterized the synthesized nanoparticles. Experimental variables were studied and optimized by the one-factor-at-a-time approach and Box-Behnken design. All antibiotics showed good linearity, with correlation coefficients of more than 0.995. The matrix effects were greatly minimized using the proposed method. The range of average recoveries was from 85.9 to 107.5%, and precision values were presented as RSDs, which were below 9.2%. The limits of detection were 0.04–0.19 μg kg−1. The measurement uncertainty was estimated by the bottom-up approach. The conformity method was applied in the analysis of real milk samples. Antibiotic residues were found in 124 samples out of 241 milk samples. Nevertheless, it was found that 24 of 133 raw cow milk samples and 15 of 108 pasteurized milk samples were above maximum residue limits. Finally, the potential human health risk estimated using the hazard quotient approach, based on the estimated daily intake and acceptable daily intake, showed a negligible risk for human health from milk consumption.

New family of Type V eutectic solvents based on 1,10-phenanthroline and their application in metal extraction

Although a theoretically extensive number of hydrophobic eutectic mixtures suitable for solvent extraction are obtainable, to date reported mixtures rely on a limited number of chelating groups, namely phosphine oxide, carboxylic acid, and ketones. Herein, a new family of Type V Deep Eutectic Solvents (DES) based on the polypyridyl ligand 1,10-phenanthroline (phen) is presented with the aim of facilitating the extrapolation of the disclosed findings to other potential systems based on phen or bipyridine derivatives. The hydrophobic eutectic solvent composed of the natural phenolic extract thymol with phen exhibits a solid-liquid phase diagram with a useable liquidus compositional range on the thymol-rich side. The physical properties of the mixture are dependent on the presence of solutes liable to change the nature of the existing hydrogen-bonded network, most notably through the protonation of phen. The metal chelating ability of phen are retained when included as a DES component. Quantitative extraction of various transition metals cations (Cd(II), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II)) as well as the platinum group metal Pd(II) was obtained across a range of solvent compositions. The extraction of Li(I), Mn(II), Co(II) and Ni(II) was further studied as a function of the aqueous phase pH, with the extent of metal partition decreasing with the protonation of phen at pH values below 1.0. Building upon the luminescent properties of phen, the eutectic solvent was further applied as a simultaneous pre-concentration and quantification medium for Fe(II/III), allowing for the facile UV–vis detection of Fe up to 12 μg L−1.