Hybrid Materials Formed with Green Metal-Organic Frameworks and Polystyrene as Sorbents in Dispersive Micro-Solid-Phase Extraction for Determining Personal Care Products in Micellar Cosmetics.

Hybrid materials based on polystyrene (PS) and green metal-organic frameworks (MOFs) were synthesized, characterized, and evaluated as potential sorbents in dispersive micro-solid-phase extraction (µ-dSPE). Among the resulting materials, the hybrid PS/DUT-67(Zr) was selected as the adequate extraction material for the monitoring of six personal care products in micellar cosmetic samples, combining the µ-dSPE method with ultra-high performance liquid chromatography (UHPLC) coupled to ultraviolet/visible detection (UV/Vis). Univariate studies and a factorial design were performed in the optimization of the microextraction procedure. The compromise optimum extraction conditions included 20 mg of PS/DUT-67(Zr) for 10 mL of sample, 2 min of extraction time, and two desorption steps using 100 µL of acetonitrile and 5 min assisted by vortex in each one. The validated µ-dSPE-UHPLC-UV/Vis method presented limits of detection and quantification down to 3.00 and 10.0 µg·L-1, respectively. The inter-day precision values were lower than 23.5 and 21.2% for concentration levels of 75 µg·L-1 and 650 µg·L-1, respectively. The hydrophobicity of the resulting PS/DUT-67(Zr) material was crucial for the improvement of its extraction capacity in comparison with its unitary components, showing the advantages of combining MOFs with other materials, getting new sorbents with interesting properties.

Using Design of Experiments to Optimize a Screening Analytical Methodology Based on Solid-Phase Microextraction/Gas Chromatography for the Determination of Volatile Methylsiloxanes in Water.

Volatile methylsiloxanes (VMSs) constitute a group of compounds used in a great variety of products, particularly personal care products. Due to their massive use, they are continually discharged into wastewater treatment plants and are increasingly being detected in wastewater and in the environment at low concentrations. The aim of this work was to develop and validate a fast and reliable methodology to screen seven VMSs in water samples, by headspace solid-phase microextraction (HS-SPME) followed by gas chromatography with flame ionization detection (GC-FID). The influence of several factors affecting the extraction efficiency was investigated using a design of experiments approach. The main factors were selected (fiber type, sample volume, ionic strength, extraction and desorption time, extraction and desorption temperature) and optimized, employing a central composite design. The optimal conditions were: 65 µm PDMS/Divinylbenzene fiber, 10 mL sample, 19.5% NaCl, 39 min extraction time, 10 min desorption time, and 33 °C and 240 °C as extraction and desorption temperature, respectively. The methodology was successfully validated, showing low detection limits (up to 24 ng/L), good precision (relative standard deviations below 15%), and accuracy ranging from 62% to 104% in wastewater, tap, and river water samples.

High-throughput microscale extraction using ionic liquids and derivatives: A review.

Ionic liquids and derivatives-mainly polymeric ionic liquids and magnetic ionic liquids-have been extensively used in microscale extraction over the past few years. Current trends in analytical sample preparation gear toward linking microextraction approaches with high-throughput sample processing to comply with green analytical chemistry requirements. A variety of high sample throughput strategies that are coupled to both ionic-liquid-based solid-phase microextraction and ionic liquid-based liquid-phase microextraction are herein reported. The review is focused on microscale extraction methods that use (i) custom-made and dedicated extraction devices, (ii) parallel extraction, (iii) magnetic-based separation, and (iv) miniaturized systems employing semi-automatic or fully automatic flow injection methods, related micro/millifluidic devices, and robotic equipment.

Evaluation of Structurally Different Ionic Liquid-Based Surfactants in a Green Microwave-Assisted Extraction for the Flavonoids Profile Determination of Mangifera sp. and Passiflora sp. Leaves from Canary Islands.

Aqueous solutions of ionic liquids (ILs) with surface active properties were used as extraction solvents, taking advantage of their impressive solvation properties, in a green microwave-assisted solid-liquid extraction method (IL-MA-SLE) for the extraction of flavonoids from passion fruit and mango leaves. The extraction method was combined with high-performance liquid chromatography and photodiode-array detection (HPLC-PDA) and optimized by response surface methodology using the Box-Behnken experimental design. Under optimum conditions, the extraction efficiency of six structurally different IL-based surfactants was evaluated. Thus, imidazolium-, guanidinium- and pyridinium-type ILs with different tailorable characteristics, such as side chain length and multicationic core, were assessed. The decylguanidinium chloride ([C10Gu+][Cl-]) IL-based surfactant was selected as key material given its superior performance and its low cytotoxicity, for the determination of flavonoids of several samples of Passiflora sp. and Mangifera sp. leaves from the Canary Islands, and using as target analytes: rutin, quercetin and apigenin. The analysis of 50 mg of plant material only required 525 µL of the low cytotoxic IL-based surfactant solution at 930 mM, 10.5 min of microwave irradiation at 30 °C and 50 W, which involves a simpler, faster, more efficient and greener method in comparison with other strategies reported in the literature for obtaining bioactive compounds profiles from plants.

Sustainable Micro-Scale Extraction of Bioactive Phenolic Compounds from Vitis vinifera Leaves with Ionic Liquid-Based Surfactants.

This paper proposes a new sustainable and simple strategy for the micro-scale extraction of phenolic compounds from grapevine leaves with analytical purpose. The method is based on a microwave-assisted solid-liquid extraction approach (MA-SLE), using an aqueous solution of an ionic liquid (IL)-based surfactant as extraction phase. The method does not require organic solvents, nor any clean-up step, apart from filtration prior to the injection in the analytical system. Two IL-based surfactants were evaluated, and the method was optimized by using experimental designs, resulting in the use of small amounts of sample (100 mg) and extraction phase (2.25 mL), low concentrations of the selected 1-hexadecyl-3-butyl imidazolium bromide IL (0.1 mM), and 30 min of extraction time. The proposed methodology was applied for the determination of the polyphenolic pattern of six different varieties of Vitis vinifera leaves from the Canary Islands, using high-performance liquid chromatography and photodiode array detection for the quantification of the compounds. The proposed MA-SLE approach was greener, simpler, and more effective than other methods, while the results from the analysis of the leaves samples demonstrate that these by-products can be exploited as a source of natural compounds for many applications.

Braid solid-phase microextraction of polycyclic aromatic hydrocarbons by using fibers coated with silver-based nanomaterials in combination with HPLC with fluorometric detection.

Authors propose a novel braid support configuration for use in solid-phase microextraction (SPME) fibers. Two different braided supports (double and triple) were prepared and compared with the conventional single support configuration. Three kinds of silver-based nanomaterials that serve as coatings on these supports are described. They included silver dendrites, silver nanoparticles (AgNPs), and silver dendrites decorated with AgNPs (Ag-dendrites@AgNPs). They were prepared by electrodeposition, a layer-by-layer (LBL) method, and a hybrid strategy, respectively. Fibers were used in the direct-immersion (DI) mode of SPME. Five polycyclic aromatic hydrocarbons (PAHs) were studied as model analytes by DI-SPME when analyzing (spiked) underground waters. PAHs were further determined with high-performance liquid chromatography (HPLC) and fluorescence detection. The analytical performance of the fibers was compared to that of the commercial polydimethylsiloxane (PDMS) fiber of 100 µm thickness. AgNPs obtained by LBL was the best coating and the double braid was the best support configuration. The configuration of the SPME support always played an important role independently on the coating material, being always beneficial the use of double-braids. Despite the low coatings volumes of the silver-based fibers compared to that of PDMS, the analytical features of the method were adequate. Figures of merit include: (a) limits of detection down to 20 ng·L-1; (b) intra-day, inter-day, and inter-fiber precisions (expressed as RSDs) of <13%, <12%, and < 13%, respectively; and (c) adequate operational lifetime (>60 extractions). Graphical abstract Schematic presentation of braided solid-phase microextraction support configurations together with different silver-based nanomaterials as coatings.

Mixed Functionalization of Organic Ligands in UiO-66: A Tool to Design Metal-Organic Frameworks for Tailored Microextraction.

The mixed-ligand strategy was selected as an approach to tailor a metal-organic framework (MOF) with microextraction purposes. The strategy led to the synthesis of up to twelve UiO-66-based MOFs with different amounts of functionalized terephthalate ligands (H-bdc), including nitro (-NO2) and amino (-NH2) groups (NO2-bdc and NH2-bdc, respectively). Increases of 25% in ligands were used in each case, and different pore environments were thus obtained in the resulting crystals. Characterization of MOFs includes powder X-ray diffraction, infrared spectroscopy, and elemental analysis. The obtained MOFs with different degrees and natures of functionalization were tested as sorbents in a dispersive miniaturized solid-phase extraction (D-µSPE) method in combination with high-performance liquid chromatography (HPLC) and diode array detection (DAD), to evaluate the influence of mixed functionalization of the MOF on the analytical performance of the entire microextraction method. Eight organic pollutants of different natures were studied, using a concentration level of 5 µg· L-1 to mimic contaminated waters. Target pollutants included carbamazepine, 4-cumylphenol, benzophenone-3, 4-tert-octylphenol, 4-octylphenol, chrysene, indeno(1,2,3-cd)pyrene, and triclosan, as representatives of drugs, phenols, polycyclic aromatic hydrocarbons, and disinfectants. Structurally, they differ in size and some of them present polar groups able to form H-bond interactions, either as donors (-NH2) or acceptors (-NO2), permitting us to evaluate possible interactions between MOF pore functionalities and analytes' groups. As a result, extraction efficiencies can reach values of up to 60%, despite employing a microextraction approach, with four main trends of behavior being observed, depending on the analyte and the MOF.

Application of a Pillared-Layer Zn-Triazolate Metal-Organic Framework in the Dispersive Miniaturized Solid-Phase Extraction of Personal Care Products from Wastewater Samples.

The pillared-layer Zn-triazolate metal-organic framework (CIM-81) was synthesized, characterized, and used for the first time as a sorbent in a dispersive micro-solid phase extraction method. The method involves the determination of a variety of personal care products in wastewaters, including four preservatives, four UV-filters, and one disinfectant, in combination with ultra-high performance liquid chromatography and UV detection. The CIM-81 MOF, constructed with an interesting mixed-ligand synthetic strategy, demonstrated a better extraction performance than other widely used MOFs in D-µSPE such as UiO-66, HKUST-1, and MIL-53(Al). The optimization of the method included a screening design followed by a Doehlert design. Optimum conditions required 10 mg of CIM-81 MOF in 10 mL of the aqueous sample at a pH of 5, 1 min of agitation by vortex and 3 min of centrifugation in the extraction step; and 1.2 mL of methanol and 4 min of vortex in the desorption step, followed by filtration, evaporation and reconstitution with 100 µL of the initial chromatographic mobile phase. The entire D-µSPE-UHPLC-UV method presented limits of detection down to 0.5 ng·mL-1; intra-day and inter-day precision values for the lowest concentration level (15 ng·mL-1)-as a relative standard deviation (in %)-lower than 8.7 and 13%, respectively; average relative recovery values of 115%; and enrichment factors ranging from ~3.6 to ~34. The reuse of the CIM-81 material was assessed not only in terms of maintaining the analytical performance but also in terms of its crystalline stability.

Salt-induced ionic liquid-based microextraction using a low cytotoxic guanidinium ionic liquid and liquid chromatography with fluorescence detection to determine monohydroxylated polycyclic aromatic hydrocarbons in urine.

A novel ionic liquid (IL)-based microextraction method has been developed for the determination of four hydroxylated polycyclic aromatic hydrocarbons (OHPAHs) in urine samples. The water soluble IL-based surfactant selected as extraction solvent is decylguanidinium chloride (C10Gu-Cl), the cytotoxicity and micellar behavior of which were evaluated. The proposed salt-induced IL-based preconcentration method simply consists in adding NaClO4 to the aqueous medium containing the IL to promote its water insolubility. The entire method was optimized, requiring the use of only 20 µL of C10Gu-Cl for 10 mL of diluted urine sample (1:10) without any pH adjustment, followed by the addition of NaClO4 to ensure a 5% (w/v) content. A cloudy solution was observed immediately, and after the application of 4 min of vortex and 8 min of centrifugation, the droplet was diluted up to 60 µL with a mixture of acetonitrile:water (30:70) and injected into the liquid chromatograph with fluorescence detection. The method was validated using both synthetic urine and human urine as matrix for the determination of the four OHPAHs. The following analytical features were obtained: detection limits down to 1 ng·L-1 in real urine; inter-day reproducibility (as RSD in %) always lower than 17% when dealing with real urine samples spiked at 80 ng·L-1; and average relative recoveries of 102% in real urine samples at such low spiked levels. Despite the simplicity of the proposed method, it performed successfully with complex urine samples. Graphical abstract Salt-induced IL-based microextraction using a low cytotoxic IL for mono-OHPAHs in urine.

Silver nanoparticles supported onto a stainless steel wire for direct-immersion solid-phase microextraction of polycyclic aromatic hydrocarbons prior to their determination by GC-FID.

The authors describe a new coating for use in solid-phase microextraction (SPME). Silver nanoparticles (AgNPs) were prepared by using gallic acid or glucose as the reducing agents, and then supported onto a stainless steel wire that was previously coated with a silver mirror. Coating with AgNPs was performed by a layer-by-layer approach of up to eight cycles of consecutive deposition of AgNPs and the thiol linker 1,8-octanedithiol. This procedure allows proper control of the coating thickness. Thicknesses are 3.2 µm and 3.5 µm with AgNPs obtained with gallic acid and glucose, respectively. This is in agreement with theoretical estimations (3.8 µm). The fibers were used in the direct-immersion SPME-GC-FID determination of 16 polycyclic aromatic hydrocarbons (PAHs) from different waters. The performance of the method was compared to the one using polydimethylsiloxane fibers (100 µm), which is the most suitable commercial SPME fiber for PAHs. Despite the low thickness of the AgNP coatings (compared to PDMS), the analytical features of the method using the most adequate coating (AgNPs prepared with gallic acid) include: (a) limits of detection down to 0.6 ng·mL-1; (b) intra-day, inter-day, and inter-fiber precisions (expressed as RSDs) lower than 22, 26 and 25%, respectively; and (c) an operational lifetime of ~150 extractions/desorption cycles. The analysis of various spiked environmental waters using these fibers resulted in adequate analytical performance. Graphical abstract Silver nanoparticle based coatings for solid-phase microextraction fibers were prepared by a layer-by-layer approach. They were used for determination of 16 PAHs in waters by gas chromatography. Limits of detection are < 14 µg·L-1 and intra-day, inter-day, and inter-fiber precisions are <26%.

Influence of Ligand Functionalization of UiO-66-Based Metal-Organic Frameworks When Used as Sorbents in Dispersive Solid-Phase Analytical Microextraction for Different Aqueous Organic Pollutants.

Four metal-organic frameworks (MOFs), specifically UiO-66, UiO-66-NH2, UiO-66-NO2, and MIL-53(Al), were synthesized, characterized, and used as sorbents in a dispersive micro-solid phase extraction (D-µSPE) method for the determination of nine pollutants of different nature, including drugs, phenols, polycyclic aromatic hydrocarbons, and personal care products in environmental waters. The D-µSPE method, using these MOFs as sorbents and in combination with high-performance liquid chromatography (HPLC) and diode-array detection (DAD), was optimized. The optimization study pointed out to UiO-66-NO2 as the best MOF to use in the multi-component determination. Furthermore, the utilization of isoreticular MOFs based on UiO-66 with the same topology but different functional groups, and MIL-53(Al) to compare with, allowed us for the first time to evaluate the influence of such functionalization of the ligand with regards to the efficiency of the D-µSPE-HPLC-DAD method. Optimum conditions included: 20 mg of UiO-66-NO2 MOF in 20 mL of the aqueous sample, 3 min of agitation by vortex and 5 min of centrifugation, followed by the use of only 500 µL of acetonitrile as desorption solvent (once the MOF containing analytes was separated), 5 min of vortex and 5 min of centrifugation. The validation of the D-µSPE-HPLC-DAD method showed limits of detection down to 1.5 ng·L-1, average relative recoveries of 107% for a spiked level of 1.50 µg·L-1, and inter-day precision values with relative standard deviations lower than 14%, for the group of pollutants considered.

Gold nanoparticles based solid-phase microextraction coatings for determining organochlorine pesticides in aqueous environmental samples.

The use of solid-phase microextraction coatings based on gold nanoparticles was investigated, focusing the attention on the preparation of nanoparticles with nonclassical reduction agents of HAuCl4 such as gallic acid and H2 O2 , rather than the conventional sodium citrate. All nanoparticles were characterized by diode array spectroscopy, whereas novel nanoparticles prepared with gallic acid and H2 O2 were also characterized by microscopic techniques. Solid-phase microextraction coatings were prepared with a layer-by-layer approach. Gallic acid permitted the preparation of stable nanoparticles with milder experimental conditions (1 min, room temperature) and provided the most uniform coatings (thickness ∼3 µm). Seven organochlorine pesticides were determined in different environmental waters using gas chromatography with electron capture detection. Despite the low thickness of the coatings, limits of detection of the entire method down to 0.13 µg/L were obtained. A comparison with the commercial polyacrylate in terms of the partition coefficients of the analytes to the coatings gave logarithm of the partition coefficient values two times higher with gallic acid than polyacrylate (although the commercial fiber is 28 times thicker). Interfiber relative standard deviation values ranged from 8.67 to 21.3%. Optimum fibers also presented an adequate lifetime (>100 extractions).

Anti-Acanthamoeba activity of Tunisian Thymus capitatus essential oil and organic extracts.

Acanthamoeba species are free-living amoebae widely distributed in the environment and which cause serious human infections. The treatment of Acanthamoeba infections is always very difficult and not constantly effective. More efficient drugs against Acanthamoeba must be developed and medicinal plants can be useful in this case. Our research focused on the examination of the anti-Acanthamoeba activity of the essential oil and the ethanolic-aqueous extract from Thymus capitatus L. The essential oil showed best activity with an IC50 of 2.73 µg/ml. The conducted Bio-guided fractionation of thyme extract result to the identification of two active compounds against the trophozoite stage of Acanthamoeba: thymol and 2,3-dihydroxy-p-cymene. The results have clearly shown that the investigated products may be successfully used against Acanthamoeba infections. These molecules that are found in plants may be an alternative for the development of new drugs.

XbmR, a new transcription factor involved in the regulation of chemotaxis, biofilm formation and virulence in Xanthomonas citri subsp. citri.

Xanthomonas citri subsp. citri (Xcc) is the causal agent of citrus canker. Biofilm formation on citrus leaves plays an important role in epiphytic survival of Xcc. Biofilm formation is affected by transposon insertion in XAC3733, which encodes a transcriptional activator of the NtrC family, not linked to a gene encoding a sensor protein, thus could be considered as an 'orphan' regulator whose function is poorly understood in Xanthomonas spp. Here we show that mutation of XAC3733 (named xbmR) resulted in impaired structural development of the Xcc biofilm, loss of chemotaxis and reduced virulence in grapefruit plants. All defective phenotypes were restored to wild-type levels by the introduction of PA2567 from Pseudomonas aeruginosa, which encodes a phosphodiesterase active in the degradation of cyclic diguanosine monophosphate (c-di-GMP). A knockout of xbmR led to a substantial downregulation of fliA that encodes a σ(28) transcription factor, as well as fliC and XAC0350 which are potential member of the σ(28) regulon. XAC0350 encodes an HD-GYP domain c-di-GMP phosphodiesterase. These findings suggest that XbmR is a key regulator of flagellar-dependent motility and chemotaxis exerting its action through a regulatory pathway that involves FliA and c-di-GMP.

Double salts of ionic-liquid-based surfactants in microextraction: application of their mixed hemimicelles as novel sorbents in magnetic-assisted micro-dispersive solid-phase extraction for the determination of phenols.

The use of mixed hemimicelles of ionic liquid (IL)-based surfactants in a magnetic-based micro-dispersive solid-phase extraction (m-µdSPE) approach is described. Not only is the symmetric monocationic IL-based surfactant 1,3-didodecylimidazolium bromide (C12C12Im-Br) studied for first time in m-µdSPE, but double-salt (DS) IL (DSIL)-based surfactants are also examined. Nine DSIL-based surfactants were formed by combination of C12C12Im-Br with other IL-based surfactants, including nonsymmetric monocationic and dicationic ILs combined at three different molar fractions. The analytical application was focused on the determination of a group of eight phenols, including bisphenol A, in water samples. The best results were obtained with the DSIL formed by C12C12Im-Br (molar fraction 0.5) and 1-hexadecyl-3-methylimidazolium bromide (C16MIm-Br), after proper optimization of the overall method in combination with high-performance liquid chromatography (HPLC) and diode-array detection (DAD). The optimum conditions for 100 mL of water samples require a small amount (10 mg) of Fe3O4 magnetic nanoparticles, a low content (5.0 mg of C12C12Im-Br and 3.9 mg of C16MIm-Br) of the selected DSIL, pH 11, a sonication time of 2.5 min, and an equilibration time of 5 min with the aid of NdFeB magnets, followed by elution of phenols, evaporation, and reconstitution with 0.5 mL of acetonitrile. The overall m-µdSPE-HPLC-DAD method is characterized for limits of detection down to 1.3 µg · L(-1), intraday relative standard deviations lower than 13 % (n = 3), and interday relative standard deviations lower than 17 % (n = 9), with a spiking level of 15 µg · L(-1); with enrichment factors between 15.7 and 141, and average relative recoveries of 99.9 %.

Automated direct-immersion solid-phase microextraction using crosslinked polymeric ionic liquid sorbent coatings for the determination of water pollutants by gas chromatography.

Four different crosslinked polymeric ionic liquid (PIL)-based sorbent coatings were evaluated in an automated direct-immersion solid-phase microextraction method (automated DI-SPME) in combination with gas chromatography (GC). The crosslinked PIL coatings were based on vinyl-alkylimidazolium- (ViCnIm-) or vinylbenzyl-alkylimidazolium- (ViBzCnIm-) IL monomers, and di-(vinylimidazolium)dodecane ((ViIm)2C12-) or di-(vinylbenzylimidazolium)dodecane ((ViBzIm)2C12-) dicationic IL crosslinkers. In addition, a PIL-based hybrid coating containing multi-walled carbon nanotubes (MWCNTs) was also studied. The studied PIL coatings were covalently attached to derivatized nitinol wires and mounted onto the Supelco assembly to ensure automation when acting as SPME coatings. Their behavior was evaluated in the determination of a group of water pollutants, after proper optimization. A comparison was carried out with three common commercial SPME fibers. It was observed that those PILs containing a benzyl group in their structures, either in the IL monomer and crosslinker (PIL-1-1) or only in the crosslinker (PIL-0-1), were the most efficient sorbents for the selected analytes. The validation of the overall automated DI-SPME-GC-flame ionization detector (FID) method gave limits of detection down to 135 µg · L(-1) for p-cresol when using the PIL-1-1 and down to 270 µg · L(-1) when using the PIL-0-1; despite their coating thickness: ~2 and ~5 µm, respectively. Average relative recoveries with waters were of 85 ± 14 % and 87 ± 15 % for PIL-1-1 and PIL-0-1, respectively. Precision values as relative standard deviation were always lower than 4.9 and 7.6 % (spiked level between 10 and 750 µg · L(-1), as intra-day precision). Graphical Abstract Automated DI-SPME-GC-FID using crosslinked-PILs sorbent coatings for the determination of waterpollutants.

Exploring a new generation of bimetallic magnetic ionic liquids with ultra-low viscosity in microextraction that enable direct coupling with high-performance liquid-chromatography.

BACKGROUND: The incorporation of bimetallic magnetic ionic liquids (MILs) in microextraction methods is an emerging trend due to the improved magnetic susceptibility offered by these solvents, which relies on the presence of metallic components in both the cation and the anion. This feature favors easy magnetic separation of these solvents in analytical sample preparation strategies. However, reported liquid-phase microextraction methods based on bimetallic MILs still present an important drawback in that the MILs are highly viscous, making a dispersive solvent during the microextraction procedure necessary, while also requiring a tedious back-extraction step prior to the chromatographic analysis. RESULTS: We propose for the first time a new generation of ultra-low viscosity bimetallic MILs composed of two paramagnetic Mn(II) complexes characterized by their easy usage in dispersive liquid-liquid microextraction (DLLME). The approach does not require dispersive solvent and the MIL-DLLME setup was directly combined with high-performance liquid chromatography (HPLC) and fluorescence detection (FD), without any back-extraction step. The approach was evaluated for the determination of five monohydroxylated polycyclic aromatic hydrocarbons, as carcinogenic biomarkers, in human urine. Optimum conditions of the MIL-DLLME method included the use of a low MIL volume (75 µL), a short extraction time (5 min), and no need of any dispersive solvent neither NaCl. The method presented limits of detection down to 7.50 ng L-1, enrichment factors higher than 17, and provided inter-day relative standard deviation lower than 11%. Analysis of urine samples was successfully performed, with biomarker content found at levels between 0.24 and 7.8 ng mL-1. SIGNIFICANCE: This study represents the first liquid-phase microextraction method using the new generation of low-viscous bimetallic MILs. The proposed MIL-DLLME approach represents 2 important advances with respect to previous methods employing bimetallic MILs: 1) no dispersive solvent is required, and 2) direct injection of the MIL in the HPLC is possible after minor dilution (no back extraction steps are required). Therefore, the microextraction strategy is simple, rapid, and consumes very small amounts of energy.

Utilization of an ionic liquid in situ preconcentration method for the determination of the 15 + 1 European Union polycyclic aromatic hydrocarbons in drinking water and fruit-tea infusions.

An ionic liquid (IL) in situ preconcentration method was optimized and applied to the monitoring of the 15 + 1 European Union polycyclic aromatic hydrocarbons in water and fruit-tea infusions. The optimized method utilizes 10 mL of water (or infusion) containing 38 µL of the IL 1-butyl-3-methylimidazolium chloride and a content of 36.1 g/L NaCl, which are mixed with Li-NTf2 (340 µL, 0.2 g/mL), followed by vortex (4 min) and centrifugation (5 min). The obtained microdroplet containing hydrocarbons is diluted with acetonitrile and injected into an HPLC with UV/Vis and fluorescence detection. The method presented average enrichment factors of 127 for water (tap water and bottled water) and 27 for two fruit-tea infusions; with average relative recoveries of 86.7 and 106% for water and fruit-tea infusions, respectively. The method was sensitive, with detection limits ranging from 0.001 to 0.050 ng/mL in water, and from 0.010 to 0.600 ng/mL in fruit-tea infusions, for the fluorescent hydrocarbons. Real extraction efficiencies ranged from 12.7 to 58.7% for water, and from 20.2 to 117% for the infusions. The method was also fast (~12 min) and free of organic solvents in the extraction step.

Monitoring polycyclic aromatic hydrocarbons in seawaters and wastewaters using a dispersive liquid-liquid microextraction method.

An evaluation has been made of a dispersive liquid-liquid microextraction (DLLME) procedure for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in different environmental waters including seawaters and wastewaters, using gas-chromatography (GC) with flame-ionization detection (FID). The optimized method requires 18 microL of the extractant solvent tetrachloroethylene (C2Cl4), 1 mL of acetonitrile as dispersive solvent, and 5 mL of aqueous sample. After centrifugation (5 min), 2 microL of the obtained micro-droplet containing the extracted PAHs, which varied from - 15 microL for seawaters to - 9 microL for wastewaters, is directly injected in the GC-FID. The performance of the method is characterized for average extraction efficiencies of 99.0% and 98.1% when analysing real seawaters and wastewaters, respectively, at low spiked levels (3 ng x mL(-1)); and average precision values of 8.4% as relative standard deviation. The performance of the method was also compared with conventional liquid-liquid extraction. The DLLME calibrations have been obtained in different aqueous matrices to thoroughly evaluate the matrix effect. The application of the joint-confidence ellipse F-test showed that seawaters can be simply analysed using DLLME calibrations obtained in the laboratory using deionized water. However, important caution must be taken into account when dealing with wastewater, because of matrix effects.

A tool to assess analytical sample preparation procedures: Sample preparation metric of sustainability.

Sample preparation is a key step in most analytical methods, generally regarded as the least green step of the entire procedure. The existing green metrics assess the greenness of sample preparation techniques through the evaluation of the whole analytical procedure: including sampling, sample preparation, and the final detection/quantitation. Such inclusion of the entire method makes assessing the sustainability of a newly developed sample preparation technique quite challenging, as many aspects not solely linked to the sample preparation step are unavoidably considered. Thus, an alternative metric that can explicitly and exclusively evaluate the sample preparation is proposed. The metric is simple; it reports the result with a clock-like diagram, displaying the greenness outcome of main sample preparation parameters and a total score. This new metric can differentiate closely related microextraction approaches in terms of sustainability. The metric is also open-source and can be used by downloading the Excel sheet provided.