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Background: Magnetic ionic liquids (MILs) have been explored in dispersive liquid-liquid microextraction (DLLME). Their usage allows to substitute centrifugation and/or filtration steps by a quick magnetic separation. Besides, effervescence-assisted DLLME is one of the most known options to improve the dispersion of the extractant in the sample, while allowing to avoid the consumption of external energy during dispersion. Despite these interesting features, only one study incorporates MILs containing the tetrachloroferrate anion in effervescence tablets. These MILs are highly viscous and liquid at room temperature, thus compromising the stability of the tablets when used as extraction microdevices in effervescence-assisted DLLME, and only allowing their use in the conventional MIL-DLLME mode., Results: A new class of effervescence tablets containing a Ni(II)-based MIL, that is solid at room temperature, is here proposed. This type of tablets permits their use, for first time, in the in situ DLLME mode, occurring through the transformation of a water-soluble MIL into a water-insoluble MIL microdroplet. This way, the tablet formulation included: the MIL, the metathesis reagent lithium bis[(trifluoromethyl)sulfonyl]imide, NaH 2 PO 4 and K 2 CO 3 as effervescence precursors salts, and Na 2 SO 4 as salting-out and desiccating agent. The method is combined with high-performance liquid-chromatography and both fluorescence and ultraviolet detection, for the determination of monohydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) and benzophenones (BPs), as biomarkers in urine. The method simply involved the addition of the effervescence tablet to the sample, thus taken place simultaneously the effervescence process and the metathesis reaction, without requiring any external energy consumption. The method presented limits of detection down to 10 ng L -1 for OH-PAHs and to 0.60 μg L -1 for BPs, inter-day relative standard deviations lower than 17 %, and average relative recoveries of 94 % in urine. The determined OH-PAHs contents in urine were between 0.40 and 16 μg L -1 , and between 17.8 and 334 μg L -1 for BPs., Significance: We have developed the first MIL-based effervescence tablets that are completely solid, thus improving the stability and robustness of these microdevices with respect to previously reported tablets involving MILs, while permitting to perform into the in situ DLLME mode (thus gaining in extraction efficiency). This approach including the MIL-based effervescence tablets constitutes an alternative on-site platform for the analysis of urine, as satisfactory precision, accuracy, and sensitivity are achieved despite not involving any external energy input within the analytical sample preparation setup. This method also constitutes the first application of MIL-based effervescence tablets for bioanalysis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Metal-organic frameworks (MOFs) are attractive materials used as sorbents in analytical microextraction applications for contaminants of emerging concern (CECs) from environmental liquid matrices. The demanding specs for a sorbent in the analytical application can be comprehensively studied by considering the interactions of the target analytes with the frameworks by the use of single-crystal X-ray diffraction, computational analysis, and adsorption studies, including the kinetic ones. The current study intends a better understanding of the interactions of target CECs (particularly, propylparaben (PPB) as a model) and three Zn-based layered pillared MOFs: CIM-81 [Zn 2 (tz) 2 (bdc)] (Htz = 1,2,4-triazole and H 2 bdc = 1,4-benzenedicarboxylic acid) and their amino derivatives [Zn 2 (NH 2 -tz) 2 (bdc)] CIM-82 and [Zn 2 (tz) 2 (NH 2 -bdc)] CIM-83 (NH 2 -Htz = 3-amino-1,2,4-triazole and NH 2 -H 2 bdc = 2-amino-1,4-benzenedicarboxylic acid). The crystal structures of the two solvate compounds ( dma@CIM-81 (dma = dimethylacetamide) and acetone@CIM-81 ) were solved by single-crystal X-ray diffraction to determine the points of interaction between the framework and the guest molecules. They also served as a starting point for the computational modeling of the PPB@CIM-81 compound, showing that up to two PPB molecules can be hosted in one of the pores, while only one can be trapped in the second pore type, leading to a maximum theoretical capacity of 291.9 mg g -1 . This value is close to the value obtained by the adsorption isotherm experiment for CIM-81 (283 mg g -1 ). This value is, by far, higher than those previously reported for other materials for the removal of PPB from water, and also higher than the experimental values obtained for CIM-82 (54 mg g -1 ) and CIM-83 (153 mg g -1 ). The kinetics of adsorption is not very fast, with uptake of about 40% in 3 h, although a 70% release in methanol is achieved in 1 h. In addition, a further comparison of performance in analytical microextraction (requiring only 10 mg of CIM-81 ) was carried out together with chromatographic analysis to support all insights attained, with the method being able to monitor CECs as low as μg L -1 levels in complex environmental water samples, thus performing successfully for water monitoring even in multicomponent scenarios.

A headspace solid-phase microextraction (HS-SPME) method was developed using the metal-organic framework (MOF) CIM-80(Al) as extraction phase and in combination with gas chromatography-mass spectrometry (GC-MS) for the simultaneous determination of 6 methylsiloxanes and 7 musk fragrances in different environmental waters. The chromatographic separation was optimized in different GC instruments equipped with different detectors, allowing the correct separation and identification of the compounds. The HS-SPME method was optimized using a Box-Behnken experimental design, while the validation was carried out together with the most suitable commercial fiber (divinylbenzene/polydimethylsiloxane) for comparison purposes. The MOF-based coating was particularly efficient for the determination of volatile methylsiloxanes, showing moderately lower limits of detection (of 0.2 and 0.5 μg L -1 versus 0.6 μg L -1 for cyclic methylsiloxanes) and slightly better precision (relative standard deviation values lower than 17% versus 22%) than the commercial coating, while avoiding the cross-contamination issues associated to the polymeric composition of commercial fibers. The method was applied for the analysis of seawater and wastewater samples, allowing the quantification of several analytes and the assessment of matrix effects. The proposed HS-SPME method using the CIM-80(Al) fiber constitutes a more environmentally friendly, simpler, and efficient strategy in comparison with other sample preparation methods using different extraction techniques, while the use of a MOF as fiber sorbent constitutes a potential alternative to exploit the features of SPME for the challenging environmental monitoring of these compounds., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

A miniaturized extraction/preconcentration method based on an aqueous biphasic system (μ-ABS) was developed with reagents commonly used as food additives: cholinium chloride (ChCl) as main extraction phase, K 2 HPO 4 as salting-out agent, and water as the main component (being the sample for analyses). With the aim of obtaining high enrichment factors, miniaturization, and adequate analytical performance, a point in the biphasic region with the lowest amount of ChCl was selected, corresponding to 1.55% (w/w) of ChCl, 59.5% (w/w) of K 2 HPO 4 , and 38.95% (w/w) of water. The green μ-ABS (attending to its main elements and performance mode) was used in combination with high-performance liquid chromatography with diode-array detection (HPLC-DAD) for the determination of 9 personal care products in wastewater samples. The μ-ABS-HPLC-DAD method showed high enrichment factors (up to 100), and quantitative extraction efficiencies for those compounds containing OH groups in their structure, which can undergo hydrogen bonding with ChCl. Thus, limits of quantification down to 0.8 µg·L -1 and extraction efficiencies between 66.4 and 108% (concentration levels of 1.3 and 13 µg·L -1 ) were reached for the group of parabens and the UV-filter benzophenone-3. The method is characterized by the use of non-harmful reagents and the absence of organic solvents in the entire sample preparation procedure, while being simple, low-cost, easily compatible with HPLC, and highly efficient., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 The Author(s). Published by Elsevier B.V. All rights reserved.)

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 ([C 10 Gu + ][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.

A new solid-phase microextraction (SPME) fiber coating was prepared by the immobilization of the metal-organic framework (MOF) CIM-80(Al) on nitinol wires by a green in situ growth approach, using an aqueous synthetic approach, and without the need of any additional material to ensure the attachment of the MOF to the nitinol support. The coating was used for the development of headspace (HS) and direct immersion (DI) SPME methods in combination with gas chromatography and mass spectrometry (GC-MS) for the determination of polycyclic aromatic hydrocarbons (PAHs) as model compounds. Both methods were optimized and validated using the MOF-based fiber together with the commercial polydimethylsiloxane (PDMS) fiber. The MOF extraction phase exhibited superior analytical performance for most of the PAHs in HS-SPME mode (and particularly for less volatiles), while the PDMS fiber presented better results in the DI-SPME method. The analytical performance of the MOF sorbent coating in HS- and DI-SPME methods was also evaluated in urine and brewed coffee samples, without requiring any pretreatment step apart from dilution for DI-SPME experiments, thus showing suitability of the novel coatings for the analysis of complex samples. The proposed CIM-80(Al) fiber was efficient and biocompatible (for using a low cytotoxic sorbent and a biocompatible core support), and it also demonstrated stability and robustness, with inter-fiber (and inter-day) relative standard deviation values lower than 19%, and reusability for more than 80 extraction cycles using 280 °C as desorption temperature., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Chemical vapor deposition of MOFs (MOF-CVD) has been used to coat solid-phase microextraction (SPME) fibers with ZIF-8, by exposing ZnO layers to the linker vapor (2-methylimidazole). This ZIF-8 coating has been used as a seed layer in a following solvothermal MOF growth step in order to increase the ZIF-8 thickness. The combined MOF-CVD and solvothermal growth of ZIF-8 on the fibers result in a thickness of ~3 μm, with adequate thermal stability, and mechanical integrity when tested with methanol and acetonitrile ultrasonic treatments. The fibers have been evaluated in direct immersion mode using gas chromatography and flame ionization detection (GC-FID), for a group of target analytes including three polycyclic aromatic hydrocarbons (PAHs) and five personal care products (PCPs). The optimized conditions of the SPME-GC-FID methods include low amount of aqueous sample (5 mL), stirring for 45 min at 35 °C, and desorption at 280 °C for 5 min. The method presents limits of detection down to 0.6 μg L -1 ; intra-day, inter-day and inter-batch relative standard deviation values lower than 16%, 19%, and 23%, respectively; and a lifetime higher than 70 cycles., Competing Interests: Declaration of competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

A pH-sensitive polymer based on the poly(styrene-alt-maleic anhydride) co-polymer serves as basis to develop a microextraction method (pH-HGME) in direct combination with high-performance liquid chromatography (HPLC) and fluorescence detection (FD) for the determination of seven organic compounds, including three polycyclic aromatic hydrocarbons (PAHs), three monohydroxylated PAHs and one alkylphenol, in urine. The method bases on the structural modification of the pH-sensitive polymer in the aqueous sample at a high pH value, followed by the formation and insolubilization of a hydrogel containing the preconcentrated analytes by decreasing the pH, and the direct injection of the hydrogel-rich phase in the HPLC-FD system. The optimization of the main variables permitted the selection of low amounts of aqueous sample (10 mL), which was mixed with 10 mg of co-polymer also present in a low volume (150 µL) of concentrated NaOH. The method further requires the addition of 200 µL of concentrated HCl, 3 min of stirring, and 15 min of centrifugation. This pH-HGME-HPLC-FD method presented low limits of detection, ranging from 0.001 µg L -1 to 0.09 µg L -1 in ultrapure water, average relative recoveries of 96.9% for the concentration level of 0.60 µg L -1 , and enrichment factors between 1.50 and 17.7. The proposed method also exhibited high precision, with intermediate relative standard deviations lower than 16% for a concentration level of 0.60 µg L -1 . The developed pH-HGME-HPLC-FD method performed adequately when analyzing two human urine samples provided by a non-smoker male and a smoker female, respectively. One of the target analytes (2-hydroxynaphthalene) was quantified in both samples using the standard addition method, with a predicted concentration of 7.3 ± 0.4 µg L -1 in the non-smoker male urine and 19.3 ± 0.6 µg L -1 in the smoker female urine., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

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 (-NO 2 ) and amino (-NH 2 ) groups (NO 2 -bdc and NH 2 -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 (-NH 2 ) or acceptors (-NO 2 ), 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.

Two ILs containing guanidinium cations (butylguanidinium chloride -C 4 Gu-Cl- and hexylguanidinium chloride -C 6 Gu-Cl-) were synthesized and characterized. Their cytotoxicity was also assessed, obtaining adequate CC 50 values of 680 ± 99 mg·L -1 for C 4 Gu-Cl and 135 ± 8 mg·L -1 for C 6 Gu-Cl. Miniaturized aqueous biphasic systems (μ-ABSs) were developed using amounts lower than 1% (w/w) of these synthesized guanidinium-based ILs, K 3 PO 4 as salting-out agent, and ultrapure water. The phases diagrams of both systems were determined, and the C 4 Gu-Cl-based μ-ABS was selected for the development of a microextraction method in combination with high performance liquid chromatography (HPLC) with fluorescence detection (FD) for the determination of five polycyclic aromatic hydrocarbons (PAHs) as model analytes. A point of the biphasic region of the C 4 Gu-Cl-based μ-ABS corresponding to a mixture of 0.75% (w/w) of the IL, 37.7% (w/w) of K 3 PO 4 and 61.55% (w/w) of ultrapure water, and 30 min of equilibrium time, were selected as optimum conditions to obtain high enrichment factors and proper analytical microextraction performance. The C 4 Gu-Cl-based μ-ABS-HPLC-FD method exhibited low limits of detection, between 0.010 ng·L -1 and 2.0 ng·L -1 , average relative recoveries of 96.7%, high enrichment factors ranging from 44.1 to 60.4, average extraction efficiencies of 61.7%, and intermediate precision relative standard deviations lower than 17% for a concentration level of 12 ng·L -1 . The developed method was applied successfully in the analysis of different tap water samples., (Copyright © 2019 Elsevier B.V. All rights reserved.)

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.

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.

The CIM-80 material (aluminum(iii)-mesaconate) has been synthetized in high yield through a novel green procedure involving water and urea as co-reactants. The CIM-80 material exhibits good thermal stability with a working range from RT to 350 °C with a small contraction upon desolvation. Moreover, this material is stable in water at different pH values (1-10) for at least one week, and shows a LC 50 value higher than 2 mg mL -1 . The new material has been tested in a microextraction methodology for the monitoring of up to 22 water pollutants while presenting little environmental impact: only 20 mg of CIM-80 and 500 μL of acetonitrile are needed per analysis. The analytical performance of the CIM-80 in the microextraction strategy is similar to or even better for several pollutants than that of MIL-53(Al). The average extraction efficiencies range from ∼20% for heavy polycyclic aromatic hydrocarbons to ∼70-100% for the lighter ones. In the case of the emerging contaminants, the average extraction efficiency can reach values up to 70% for triclosan and carbamazepine., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The IL-based surfactant octylguanidinium chloride (C 8 Gu-Cl) was designed and synthetized with the purpose of obtaining a less harmful surfactant: containing guanidinium as core cation and a relatively short alkyl chain. Its interfacial and aggregation behavior was evaluated through conductivity and fluorescence measurements, presenting a critical micelle concentration value of 42.5 and 44.6mmolL -1 , respectively. Cytotoxicity studies were carried out with C 8 Gu-Cl and other IL-based and conventional surfactants, specifically the analogue 1-octyl-3-methylimidazolium chloride (C 8 MIm-Cl), and other imidazolium- (C 16 MIm-Br) and pyridinium- (C 16 Py-Cl) based surfactants, together with the conventional cationic CTAB and the conventional anionic SDS. From these studies, C 8 Gu-Cl was the only one to achieve the classification of low cytotoxicity. An in situ dispersive liquid-liquid microextraction (DLLME) method based on transforming the water-soluble C 8 Gu-Cl IL-based surfactant into a water-insoluble IL microdroplet via a simple metathesis reaction was then selected as the extraction/preconcentration method for a group of 6 personal care products (PCPs) present in cosmetic samples. The method was carried out in combination with high-performance liquid chromatography (HPLC) and diode array detection (DAD). The method was properly optimized, requiring the use of only 30μL of C 8 Gu-Cl for 10mL of aqueous sample with a NaCl content of 8% (w/v) to adjust the ionic strength and pH value of 5. The metathesis reaction required the addition of the anion exchange reagent (bis[(trifluoromethyl)sulfonyl]imide - 1:1 molar ratio), followed by vortex and centrifugation, and dilution of the final microdroplet up to 60μL with acetonitrile before the injection in the HPLC-DAD system. The optimum in situ DLLME-HPLC-DAD method takes ∼10min for the extraction step and ∼22min for the chromatographic separation, with analytical features of low detection limits: down to 0.4μgL -1 ; high reproducibility: with RSD values lower than 10% (intra-day) and 16% (inter-day) for a spiked level of 15μgL -1 ; and an average enrichment factor of 89. The requirement of low volumes (30μL) of a low cytotoxic IL-based surfactant allows the method to be considered less harmful than other common analytical microextraction approaches., (Copyright © 2017 Elsevier B.V. All rights reserved.)

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 (C 10 Gu-Cl), the cytotoxicity and micellar behavior of which were evaluated. The proposed salt-induced IL-based preconcentration method simply consists in adding NaClO 4 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 C 10 Gu-Cl for 10 mL of diluted urine sample (1:10) without any pH adjustment, followed by the addition of NaClO 4 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.

Five metal-organic frameworks (MOFs), specifically HKUST-1, MOF-5(Zn), MIL-53(Al), UiO-64 and MOF-74(Zn) are synthesized, characterized, and utilized in a miniaturized solid-phase extraction method under dispersive mode (D-µSPE) for the determination of six pollutants of different nature, including one polycyclic aromatic hydrocarbon, two hormones, two drugs, and one disinfectant, from environmental waters (tap water and wastewater). A discussion of possible interactions justifying the partitioning of target analytes to the MOFs is included, considering not only the analytes' physicochemical characteristics but also those of MOFs: metal nature, structural environment of MOF pores, pore size and pore aperture widths, among others. MIL-53(Al) is selected for its versatility and high extraction efficiency for the target compounds. The D-µSPE method using MIL-53(Al) is optimized and used in combination with high-performance liquid chromatography (HPLC) with diode array detector (DAD) or liquid-chromatography with time-of-flight mass spectrometric detector (LC-TOF). Under optimum conditions, only 5mg of MIL-53(Al) are required for 10mL of water, with the aid of 5min of vortex and 5min of centrifugation. Elution is accomplished with 200µL of acetonitrile (3 times), and evaporation down to 100µL before LC injection. Detection limits down to 0.040μgL -1 for triclosan and 0.013μgL -1 for atrazine are obtained for the entire method using HPLC-DAD and LC-TOF, respectively. The method, operating at low spiked levels (2µgL -1 for HPLC-DAD and 0.7µgL -1 for LC-TOF), is also characterized for average relative recoveries of 109% and 105%; relative standard deviation values lower than 8.7% and 7.5%; and average extraction efficiencies of 41.2% and 49.1%; using HPLC-DAD and LC-TOF, respectively; while demonstrating adequate analytical performance with complex samples such as wastewaters., (Copyright © 2017 Elsevier B.V. All rights reserved.)

This work proposes a new vacuum headspace solid-phase microextraction (Vac-HSSPME) method combined to gas chromatography-flame ionization detection for the determination of free fatty acids (FFAs) and phenols. All target analytes of the multicomponent solution were volatiles but their low Henry's Law constants rendered them amenable to Vac-HSSPME. The ability of a new and easy to construct Vac-HSSPME sampler to maintain low-pressure conditions for extended sampling times was concurrently demonstrated. Vac-HSSPME and regular HSSPME methods were independently optimized and the results were compared at all times. The performances of four commercial SPME fibers and two polymeric ionic liquid (PIL)-based SPME fibers were evaluated and the best overall results were obtained with the adsorbent-type CAR/PDMS fiber. For the concentrations used here, competitive displacement became more intense for the smaller and more volatile analytes of the multi-component solution when lowering the sampling pressure. The extraction time profiles showed that Vac-HSSPME had a dramatic positive effect on extraction kinetics. The local maxima of adsorbed analytes recorded with Vac-HSSPME occurred faster, but were always lower than that with regular HSSPME due to the faster analyte-loading from the multicomponent solution. Increasing the sampling temperature during Vac-HSSPME reduced the extraction efficiency of smaller analytes due to the enhancement in water molecule collisions with the fiber. This effect was not recorded for the larger phenolic compounds. Based on the optimum values selected, Vac-HSSPME required a shorter extraction time and milder sampling conditions than regular HSSPME: 20 min and 35 °C for Vac-HSSPME versus 40 min and 45 °C for regular HSSPME. The performance of the optimized Vac-HSSPME and regular HSSPME procedures were assessed and Vac-HSSPME method proved to be more sensitive, with lower limits of detection (from 0.14 to 13 μg L -1 ), and better intra-day precision (relative standard deviations values < 10% at the lowest spiked level) than regular HSSPME for almost all target analytes. The proposed Vac-HSSPME method was successfully applied to quantify FFAs and phenols in milk and milk derivatives samples., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A simple and efficient method has been developed for the extraction and determination of 16 common volatile halogenated disinfection by-products (DBPs) (four trihalomethanes, six haloacetonitriles, and six halonitromethanes) in blending desalinated waters, using headspace solid-phase microextraction and gas chromatography with flame ionization detector (HS-SPME/GC-FID). After the optimization using factorial designs of the HS-SPME parameters (optimum: carboxen/polydimethylsiloxane such as fiber, extraction time of 60 min at 30°C, pH 7, addition of 40% (w/v) of sodium chloride, and desorption time of 2 min at 250°C), quantification limits ranged from 3.03 to 40.8 µg L -1 , and relative standard deviation (inter-day) were lower than 9.7% for all the target DBPs. Adequate relative recoveries (with the exception of chloronitromethane) were obtained even when spiking waters at low levels (25 µg L -1 ), with values between 83.1% and 119% for ultrapure water, and between 87.4% and 115% for blending desalinated waters, supporting in this way the applicability of the method. The influence of various dechlorinating agents on the stability of 16 DBPs in water was evaluated, with ammonium chloride being the most suitable inhibitor of residual chlorine and carrying out the analytical determination of DBPs within 48 h after sampling. Different blending desalinated water samples collected in the South of Tenerife Island (Spain) were successfully analyzed.

Free fatty acids and sensory profiles were obtained for cheeses made with raw goat milk and vegetable coagulant, derived from the cardoon flower ( Cynara cardunculus), at different ripening times (7 and 20 days). A solid-liquid phase extraction method followed by solid-phase extraction and gas chromatography was used. Profiles were also obtained with cheeses made with commercial coagulant, traditional kid rennet paste, and mixture coagulant (vegetable coagulant-kid rennet). The use of vegetable coagulant and vegetable coagulant-kid rennet is common in traditional Protected Designation of Origin cheeses such as " Queso Flor de Guía" and " Queso Media Flor de Guía" (Spain). Contents of short-chain free fatty acids (7.5-22.5 mmol·kg -1 ), medium-chain free fatty acids (0.4-3.7 mmol·kg -1 ), and long-chain free fatty acids (0.2-2.1 mmol·kg -1 ) varied depending on the coagulant type and the ripening time. Vegetable coagulant cheeses present odour intensity and flavour intensity much higher than commercial coagulant cheeses in the sensory analysis for cheeses obtained with seven days of ripening, but the values decrease when increasing the ripening time. Multivariate analysis allowed us to differentiate cheese samples according to the ripening time when using lipolytic profile and according to the coagulant type using the sensory profile.

The environmental monitoring of trihalomethanes (THMs) has been performed by setting up a dispersive liquid-liquid microextraction method in combination with gas chromatography (GC)-mass spectrometry (MS). The optimized method only requires ∼26 µL of decanol as extractant solvent, dissolved in ∼1 mL of acetone (dispersive solvent) for 5 mL of the environmental water containing THMs. The mixture is then subjected to vortex for 1 min and then centrifuged for 2 min at 3500 rpm. The microdroplet containing the extracted THMs is then sampled with a micro-syringe, and injected (1 µL) in the GC-MS. The method is characterized for being fast (3 min for the entire sample preparation step) and environmentally friendly (low amounts of solvents required, being all non-chlorinated), and also for getting average relative recoveries of 90.2-106% in tap waters; relative standard deviation values always lower than 11%; average enrichment factors of 48-49; and detection limits down to 0.7 µg·L-1. Several waters: tap waters, pool waters, and wastewaters were successfully analyzed with the method proposed. Furthermore, the method was used to monitor the formation of THMs in wastewaters when different chlorination parameters, namely temperature and pH, were varied.

Several crosslinked polymeric ionic liquid (PIL)-based sorbent coatings of different nature were prepared by UV polymerization onto nitinol wires. They were evaluated in a direct-immersion solid-phase microextraction (DI-SPME) method in combination with high-performance liquid chromatography (HPLC) and diode array detection (DAD). The studied PIL coatings contained either vinyl alkyl or vinylbenzyl imidazolium-based (ViCnIm- or ViBCnIm-) IL monomers with different anions, as well as different dicationic IL crosslinkers. The analytical performance of these PIL-based SPME coatings was firstly evaluated for the extraction of a group of 10 different model analytes, including hydrocarbons and phenols, while exhaustively comparing the performance with commercial SPME fibers such as polydimethylsyloxane (PDMS), polyacrylate (PA) and polydimethylsiloxane/divinylbenzene (PDMS/DVB), and using all fibers under optimized conditions. Those fibers exhibiting a high selectivity for polar compounds were selected to carry out an analytical method for a group of 5 alkylphenols, including bisphenol-A (BPA) and nonylphenol (n-NP). Under optimum conditions, average relative recoveries of 108% and inter-day precision values (3 non-consecutive days) lower than 19% were obtained for a spiked level of 10µgL(-1). Correlations coefficients for the overall method ranged between 0.990 and 0.999, and limits of detection were down to 1µgL(-1). Tap water, river water, and bottled water were analyzed to evaluate matrix effects. Comparison with the PA fiber was also performed in terms of analytical performance. Partition coefficients (logKfs) of the alkylphenols to the SPME coating varied from 1.69 to 2.45 for the most efficient PIL-based fiber, and from 1.58 to 2.30 for the PA fiber. These results agree with those obtained by the normalized calibration slopes, pointing out the affinity of these PILs-based coatings., (Copyright © 2016 Elsevier B.V. All rights reserved.)

This work describes the applicability of magnetic ionic liquids (MILs) in the analytical determination of a group of heavy polycyclic aromatic hydrocarbons. Three different MILs, namely, benzyltrioctylammonium bromotrichloroferrate (III) (MIL A), methoxybenzyltrioctylammonium bromotrichloroferrate (III) (MIL B), and 1,12-di(3-benzylbenzimidazolium) dodecane bis[(trifluoromethyl)sulfonyl)]imide bromotrichloroferrate (III) (MIL C), were designed to exhibit hydrophobic properties, and their performance examined in a microextraction method for hydrophobic analytes. The magnet-assisted approach with these MILs was performed in combination with high performance liquid chromatography and fluorescence detection. The study of the extraction performance showed that MIL A was the most suitable solvent for the extraction of polycyclic aromatic hydrocarbons and under optimum conditions the fast extraction step required ∼20 μL of MIL A for 10 mL of aqueous sample, 24 mmol L(-1) NaOH, high ionic strength content of NaCl (25% (w/v)), 500 μL of acetone as dispersive solvent, and 5 min of vortex. The desorption step required the aid of an external magnetic field with a strong NdFeB magnet (the separation requires few seconds), two back-extraction steps for polycyclic aromatic hydrocarbons retained in the MIL droplet with n-hexane, evaporation and reconstitution with acetonitrile. The overall method presented limits of detection down to 5 ng L(-1), relative recoveries ranging from 91.5 to 119%, and inter-day reproducibility values (expressed as relative standard derivation) lower than 16.4% for a spiked level of 0.4 μg L(-1) (n = 9). The method was also applied for the analysis of real samples, including tap water, wastewater, and tea infusion., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A hybrid material composed by the metal-organic framework (MOF) HKUST-1 and Fe3O4 magnetic nanoparticles (MNPs) has been synthetized in a quite simple manner, characterized, and used in a magnetic-assisted dispersive micro-solid-phase extraction (M-d-μSPE) method in combination with ultra-high-performance liquid chromatography (UHPLC) and fluorescence detection (FD). The application was devoted to the determination of 8 heavy polycyclic aromatic hydrocarbons (PAHs) in different aqueous samples, specifically tap water, wastewaters, and fruit tea infusion samples. The overall M-d-μSPE-UHPLC-FD method was optimized and validated. The method is characterized by: its simplicity in both the preparation of the hybrid material (simple mixing) and the magnetic-assisted approach (∼10min extraction time), the use of low sorbent amounts (20mg of HKUST-1 and 5mg of Fe3O4 MNPs), and the low organic solvent consumption in the overall M-d-μSPE-UHPLC-FD method (1.5mL of acetonitrile in the M-d-μSPE method and 2.8mL of acetonitrile in the UHPLC-FD run). The resulting method has high sensitivity, with LODs down to 0.8ngL(-1); adequate intermediate precision, with relative standard deviation values (RSD) always lower than 6.3% (being the range 5.9-9.0% in tap water for a spiked level of 45ngL(-1), 6.1-14% in wastewaters for a spiked level of 45ngL(-1), and 7.2-17% in fruit tea infusion samples for a spiked level of 45ngL(-1)); and adequate relative recoveries, with average values of 82% in tap water, and 94% and 75% in wastewater and fruit tea infusion samples, respectively, if using the proper matrix-matched calibration., (Copyright © 2016 Elsevier B.V. All rights reserved.)

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 %.

Three metal-organic frameworks (MOFs), specifically HKUST-1, MOF-5, and MIL-53(Al), have been synthetized, characterized, studied and compared in a vortex-assisted dispersive micro-solid-phase extraction (VA-D-µ-SPE) procedure in combination with high-performance liquid chromatography (HPLC) with diode-array detection (DAD) for determining seven parabens in environmental waters (tap water, swimming pool water, and water coming from a spa pool), human urine (from two volunteers), and cosmetic creams (two commercial brands). Experimental parameters, such as nature and amount of MOF, sample volume, nature of elution solvent and its amount, vortex and centrifugation time, among others, were properly optimized. HKUST-1 was the most adequate MOF to work with. Detection limits for the overall method down to 0.1 μgL(-1) for butylparaben (BPB) and benzylparaben (BzPB) were obtained, with determination coefficients (R(2)) higher than 0.9966 for a range of 0.5-147 μgL(-1) (depending on the paraben), average relative recoveries (RR, in %) of 80.3% at the low spiked level (7 μgL(-1)), and relative standard deviation (RSD) values below 10% also at the low spiked level. The strength of the affinity between HKUST-1 and parabens was evaluated, and it ranged from 33.5% for isopropylparaben (iPPB) to 77.0% for isobutylparaben (iBPB). When analyzing complex environmental waters, RR values of 78%, inter-day precision values (as RSD) lower than 15%, and intra-day precision values lower than 7.8% were obtained, despite the observed matrix effect. When analyzing cosmetic creams, parabens were detected, with contents ranging from 0.14 ± 0.01 μgg(-1) for EPB in the healing cream analyzed to 1.12 ± 0.07 mgg(-1) for MPB in the mask cream analyzed, with precision values (RSD) lower than 12% and RR values from 63.7% for propylparaben (PPB) to 121% for iPPB. When analyzing human urine, no parabens were detected but the method could be performed with RSD values lower than 19%. These results show the adequateness of MOFs as sorbents in VA-D-µ-SPE procedures despite sample complexity., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Multiple headspace solid-phase microextraction (MHS-SPME) has been utilized for the quantitative determination of 9 volatile free fatty acids (FFAs) in cheeses, in combination with gas-chromatography and flame-ionization detection (GC-FID). Variables affecting HS-SPME and MHS-SPME were optimized to attain adequate sensitivity while allowing correct application of the MHS method. Thus, the MHS-SPME method was successfully performed when using 0.3g of cheese and 1 mL of NaCl (sat. solution), which is subjected to four consecutive extractions using the carboxen-polydimethylsyloxane (CAR-PDMS) as the commercial SPME coating, 40 min of HS extraction time at 45°C, and 6 min of desorption time in the GC injector at 290°C. The MHS-SPME permitted the calculation of β values, which range from 0.72±0.01-0.95±0.02, depending on the cheese studied. Later, this β parameter is used to perform quantitation for the 9 volatile FFAs after just a single HS-SPME extraction, using an external solvent calibration curve. The validity of the utilization of an external solvent calibration was tested with aqueous standards of volatile FFAs, getting average recoveries higher than 81.2%. Quantitation by MHS-SPME was free of matrix interferences despite measuring a complex cheese sample. The optimized method was validated, presenting inter-day reproducibility values (as RSD in %) lower than 13%, and limits of detection down to 7 µg kg(-1). The method was also compared with a conventional extraction method such as solid-phase extraction for the studied cheeses elaborated with goat milk, generating comparable results. To our knowledge, this is the first time that MHS-SPME has been applied to volatiles in cheeses., (Copyright © 2014 Elsevier B.V. All rights reserved.)

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., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A novel and simple preconcentration step for aqueous micellar solutions of the common cationic surfactant cetyltrimethylammonium bromide (CTAB) has been developed. The procedure is based on the formation of another phase (a micro-droplet), not soluble in water, in which analytes (originally present in the aqueous solution) experience preconcentration. The method resembles to that of classical coacervation, but it does not require high ionic strengths neither acidic pH values. The optimum method implies mixing aqueous micellar solutions of CTAB with lithium bis[(trifluoromethane)sulfonyl]imide (Li-NTf₂) in a 1:1 molar ratio with a 16.5% (v/v) of acetonitrile content, followed by vortex, heating at 65 °C during 2 min, and centrifugation. The obtained microdroplet containing analytes is then subjected to high-performance liquid chromatography (HPLC) with diode-array detection (DAD). The method has been applied to the determination of a group of organic contaminants including alkylphenols, polycyclic aromatic hydrocarbons and parabens, present in aqueous samples (including seawater) or solid samples (such as sediment samples, which are subjected to a previous microwave-assisted extraction). Average preconcentration factors of roughly 14 and 12 are obtained for aqueous and sediment samples, respectively; being the limits of quantification down to 0.5 μg L⁻¹ and 0.02 mg kg⁻¹, respectively., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The determination of a group of organic contaminants from marine sediments samples including three polycyclic aromatic hydrocarbons, five alkylphenols (i.e., bisphenol-A or nonylphenol) and one paraben has been carried out using an extraction/preconcentration strategy with ionic liquid-based surfactants and high-performance liquid chromatography (HPLC) with diode array detection (DAD). Sediments are first extracted using two IL-based surfactants, specifically 1-hexadecyl-3-methyl imidazolium bromide (C(16)MIm-Br) and 1-hexadecyl-3-butyl imidazolium bromide (C(16)C(4)Im-Br), as the extraction media in a microwave-assisted extraction (MAE) procedure, followed by a novel in situ preconcentration method. The optimized MAE method requires 0.1 g of sediment and 5 mL of 40 mM C(16)MIm-Br IL solution. The extracts are then centrifuged and filtered. The subsequent preconcentration in situ approach consists of the insolubilization of an IL-based surfactant formed by a metathesis reaction using the anion-exchange reagent lithium bis[(trifluoromethane)sulfonyl]imide (LiNTf(2)), which produces an analyte enriched IL microdroplet. The optimized in situ approach utilizes 4 mL of the filtered extract, which are mixed with acetonitrile and 92 μL of LiNTf(2) solution (0.5 g mL(-1)), heated, vortexed and centrifuged. The formed IL microdroplet is then simply diluted with acetonitrile (~100 μL) and injected in the chromatograph without any further clean-up steps. The overall extraction/preconcentration method requires approximately 25 min in spite of dealing with complex solid samples, is nearly free of organic solvent (requires ~900 μL of acetonitrile per sample), and produces high preconcentration factors and quantification limits down to 0.04 mg kg(-1) using HPLC-DAD., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The content of ten phenolic compounds present in four different biomass smoke materials: rock rose (Cistus monpelienisis), prickly pear (Opuntia ficus indica), pine needles (Pinus canariensis), and almonds skin (Prunus dulcis), have been evaluated. The sampling method mainly consisted of a trap alkaline solution to solubilize the phenols, and was optimized by an experimental design. Average sampling efficiencies of 78.1% and an average precision value of 10.6% (as relative standard deviation, RSD), were obtained for the selected group of phenols. The trapped phenolates were further analyzed by a headspace-single drop microextraction (HS-SDME) procedure, in combination with high-performance liquid chromatography (HPLC) with UV detection. The optimum variables for the HS-SDME method were: 1-decanol as extractant solvent, 3.5 μL of microdrop volume, 2 mL of sample volume, a pH value of 2, saturation of NaCl, an extraction temperature of 60°C, and an extraction time of 25 min. The optimized HS-SDME method presented detection limits ranging from 0.35 to 5.8 μg mL(-1), RSD values ranging from 0.7 to 7.4%, and an average relative recovery (RR) of 99.8% and an average standard deviation of 5.2. The average content of phenolic compounds in the biomass materials studied were 70, 161, 206 and 252 mg kg(-1) of biomass for prickly pear, almonds skin, rock rose, and pine needles, respectively. The main components of the smokes were vanillin, phenol and methoxyphenols, in all smoking materials studied., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The effects of several ionic liquids (ILs) as mobile-phase additives in HPLC with fluorescence and UV-Vis detection for the determination of six heterocyclic aromatic amines were evaluated using two different C(18) stationary phases with moderate silanol activity. The studied ILs were 1-butyl-3-methylimidazolium tetrafluoroborate, 1-hexyl-3-methylimidazolium tetrafluoroborate and 1-methyl-3-octylimidazolium tetrafluoroborate. The optical behaviour of heterocyclic aromatic amines in presence of ILs was studied and the silanol-suppressing potency of ILs was evaluated for the two stationary phases studied. Several chromatographic parameters were evaluated in the presence or absence of ILs, or using triethylamine, the most common mobile-phase additive. The best results were achieved using 1 mM 1-butyl-3-methylimidazolium tetrafluoroborate as mobile-phase additive and NovaPak column. In these conditions and with 18% of ACN in the mobile phase, analytical performance of the chromatographic methods using fluorescence and UV-Vis were evaluated, obtaining good precision in all cases (RSD lower than 6.6%) and low LOD (0.001-0.147 microg/mL with UV-Vis and 0.001-0.006 ng/mL with fluorescence detection).

The beneficial effects of several ionic liquids (ILs) as mobile phase additives in high-performance liquid chromatography with electrochemical detection for the determination of six heterocyclic aromatic amines (HAs) have been evaluated for first-time. The studied ionic liquids were 1-butyl-3-methylimidazolium tetrafluoroborate (BMIm-BF(4)), 1-hexyl-3-methylimidazolium tetrafluoroborate (HMIm-BF(4)) and 1-methyl-3-octylimidazolium tetrafluoroborate (MOIm-BF(4)). Several chromatographic parameters have been evaluated in the presence or absence of ILs, or using ammonium acetate as the most common mobile phase additive, with three different C18 stationary phases. The effect of the acetonitrile content was also addressed. In general, best resolution, lower peak-widths (up to 72.1% lower) and lower retention factors are obtained when using ILs rather than ammonium acetate as mobile phase additives. The main improvement was obtained in the baseline noise, being 360% less noisy for BMIm-BF(4), 310% for HMIm-BF(4), and 227% for MOIm-BF(4), when compared to ammonium acetate at +1000 mV. Different chromatographic methods using the best conditions for each IL were also evaluated and compared. Finally, the best chromatographic conditions using 1mM of BMIm-BF(4) as mobile phase additive, the Nova-Pak C18 column, 19% (v/v) of acetonitrile content in the mobile phase, and +1000 mV in the ECD, have been applied for the chromatographic analysis of six HAs contained in meat-based infant foods. The whole extraction method of meat-based infant foods using focused microwave-assisted extraction and solid-phase extraction has also been optimized. Extraction efficiencies up to 89% and detection limits ranged between 9.30 and 0.165 ng g(-1) have been obtained under optimized conditions.

The beneficial effects of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIm-BF(4)) ionic liquid (IL) as mobile phase additive, desorption solvent, and memory effect suppressor in solid-phase microextraction (SPME)-high-performance liquid chromatography with fluorescence detection for the determination of six heterocyclic aromatic amines have been evaluated for the first time. Several chromatographic parameters have been evaluated in the presence or absence of IL or using triethylamine as the most common mobile phase additive, with a Nova-Pak C18 stationary phase. This IL was found to be clearly superior to triethylamine for efficiency as well as peak shape enhancement and sensitivity increase. SPME was chosen because it is faster than conventional extraction techniques and allowed us to minimize the use of organic solvents. However, memory effect may become a problem when a high-sensitivity detector is used. The appropriate conditions for the desorption step and to eliminate the memory effect involving BMIm-BF(4) were established and optimized. The method was applied for the determination of these compounds in commercial meat extracts.

There are significant drawbacks to the calibration procedure recommended in the normalized Spanish or American methods used to determine carbonyl compounds in ambient air by quantifying hydrazones that form with 2,4-dinitrophenylhydrazine. The impurities present in 2,4-dinitrophenylhydrazine, as well as the lack of quantitativity and the slow kinetics of some derivatization reactions can lead to considerable errors in quantification. This work proposes two alternative systems for sampling biomass smoke in order to analyze aldehydes and ketones. The standardization process used by both systems requires standard solutions to be reacted with 2,4-dinitrophenylhydrazine under experimental conditions similar to those used to collect the sample. The resulting calibration curve slopes differ between 8% and 74% from the curves used in methods that employ commercial standard hydrazone solutions. The detection limits reached by using the proposed methods are between 0.07 and 0.47 mg L(-1). Both methods are complementary for smoke samples that have significant differences in the concentrations of aldehydes or ketones.

An environmentally friendly method to extract endocrine-disrupting phenols (EDPs) from seawaters was realized using nonionic surfactant mixtures and micelle-mediated extractions. The preconcentration step was achieved directly in the seawater matrix, and was followed by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection without any clean-up steps to remove the surfactant mixture prior to injection. Various nonionic surfactant mixtures were used, and polyoxyethylene-10-laurylether (POLE) with polyoxyethylene-4-laurylether (Brij 30) was found to be the best to work with. Method optimization involved maximizing the preconcentration factor using the studied mixtures. The proposed method gave extraction recoveries ranging from 83.3 to 114.4% for an EDP spiking level of 46.7 microg L(-1), and from 63.4 to 112.4% for a spiking level of 4.7 microg L(-1) for EDPs studied in real seawater matrices, with relative standard deviations of <12.1%. The detection limits of the method varied from 0.18 microg L(-1) for bisphenol A (BPA) to 1.17 microg L(-1) for 4-cumylphenol (4-CP). The method was applied to seawaters from the Canary Islands with successful results.

A method to extract PAHs from sediments is carried out using aqueous solutions containing aggregates of the ionic liquid (IL) 1-hexadecyl-3-methylimidazolium bromide (HDMIm-Br) as the extracting medium. Focused microwave-assisted extraction has been used to accelerate the extraction step, followed by HPLC with fluorescence detection without clean-up steps to remove the IL prior to injection. The method has been applied to certified reference sediment BCR-535 and marine sediments from Tenerife (Canary Islands) with successful results. The optimized method gave average absolute recoveries of 91.1% for six of the seven PAHs studied, with relative standard deviations lower than 10.4%. The overall method is characterized for presenting low extraction times (6min), low amounts of the sediment (0.1g), low amounts of IL (45mM), and low volumes of aqueous extractant solution (9mL). The use of small amounts of both IL and aqueous extractant solution allows the method to be considered environmental-friendly.

Analytical aspects concerning the heterocyclic aromatic amines (HAAs) determination in foods are reviewed. Sample pre-treatment procedures such as liquid-liquid extraction (LLE), supercritical fluid extraction, solid-phase extraction (SPE), solid-phase microextraction (SPME), and the mainly used LLE-SPE tandem extraction are discussed. The analytical methods used for the identification and quantification are HPLC, HPLC combined with single or tandem MS detection (HPLC-MS, HPLC-MS/MS), GC-MS and capillary electrophoresis. Advantages and figures of merit for each technique are discussed.

This work combines the utilization of the micellar media during the extraction step and the focused microwave-assisted extraction followed by the solid-phase microextraction-gas chromatography/mass spectrometry (SPME-GC/MS) to determine the alkyl- and methoxy-phenolic content in wood extractives. The proposed environmental-friendly method is mainly characterized by short analysis times (5min for the microwaves extraction step) and for avoiding the use of organic solvents. Different surfactants were tried for the extraction process: the cationic surfactant CTAB and the non-ionic surfactants Triton X-100 and POLE, with similar extraction efficiencies (85.5-99.7%). The overall method presents limits of detection in the ngg(-1) region for the alkylphenols (from 7 to 150ngg(-1)) and in the mugg(-1) region for the methoxyphenols (from 0.80 to 22.9mugg(-1)). The vanillin was the compound most abundant in the wood extractives studied, with concentrations up to 116.2mgkg(-1).

Micellar solid-phase microextraction (MSPME) coupled to gas chromatography-mass spectrometry (GC-MS) has been used to obtain partition coefficients of a group of 18 substituted aromatic hydrocarbons to ionic and nonionic micelles. Statistical and factor analyses have been utilized to establish some general equations relating molecular descriptors of non-substituted polycyclic aromatic hydrocarbons and their partition coefficients obtained by MSPME. The obtained equations have correlation coefficients higher than 0.94. They are used to predict hydrocarbon-micelle partition coefficients for a group of hydrocarbons with reported literature values giving a correlation coefficient of 0.98 and a standard deviation of the prediction of 0.182. The predictive model was also applied to substituted polycyclic aromatic hydrocarbons with partition coefficient values obtained by MSPME, with a 69% level of success.

A procedure for the determination of less polar heterocyclic amines in meat extracts using solid phase microextraction (SPME) coupled to high-performance liquid chromatography (HPLC) with fluorescence detection is presented. Analytes were first extracted from the samples using methanol/NaOH by an ultrasound-assisted method, and then concentrated on a Carbowax-templated resin (CW-TPR) SPME fiber. The extraction conditions such as extractant mixture composition, extraction time and extractions number, were optimized and the need of an extract freezing step previous to SPME is discussed. The detection limits under optimal conditions are in the range of 0.28-1.1 ng g(-1). The method was applied to the determination of less polar heterocyclic amines in four commercial meat extracts. Recovery values obtained are higher than 60% for the majority of amines.

This work describes the utilization of the focused microwave-assisted micellar extraction in combination with the solid-phase microextraction (SPME) to determine chlorophenols in wood samples. The influence of the nature of the surfactant in the extraction process, the optimization of the variables of the focused-microwave system, and the effect of the ageing time of the samples in the extraction efficiency of the method, have been assessed in this study. The overall method using the non-ionic surfactant POLE as extracting medium allows us to determine chlorophenols in wood samples achieving an average extraction efficiency of 104.1%, limits of detection ranging from 2 to 120 ng g(-1), and intermediate precision values ranging between 3.5 and 13.2%. The proposed method is also characterized by short analysis times (around 5 min for the microwaves extraction step) and by avoiding the use of organic solvents.

A sampling and analysis method for the determination of 21 phenolic compounds in smoke samples from biomass combustion has been developed. The smoke is used to make smoked foods, following an artisanal procedure used in some parts of the Canary Islands. The sampling system consists of a Bravo H air sampler, two impingers, each one containing an aqueous solution of sodium hydroxide 0.1 mol L(-1), followed by a silica gel trap. The variables optimized to reach the best sampling conditions were volume of absorbent solution and sampling flow. Under the optimum conditions, 100 mL of absorbent solution of NaOH 0.10 mol L(-1) and 2 L min(-1) for the sampling flow, sampling efficiencies are higher than 80%. Analysis of phenolic compounds was carried out by headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS). Five different fiber coatings were employed in this study. By means of a central composite design, extraction time, salt concentration, and pH of the solution were optimized: 65-microm carbowax-divinylbenzene, extraction time 90 min, concentration in NaCl of 35% (m/v), and pH 2 yielded the highest response. Detection limits of phenol and their alkyl derivatives, guaiacol and eugenol, are between 1.13 and 4.60 ng mL(-1). 3-Methoxyphenol, 2,6-dimethoxyphenol, and vanillin have detection limits considerably higher. Good linearity (R2 > or = 0.98) was observed for all calibration curves in the established ranges. The reproducibility of the method (RSD, relative standard deviation) was found to oscillate between 7 and 18% (generally close or lower than 10%).

Solid-phase microextraction coupled to gas-chromatography with mass-spectrometry detection has been employed to establish the sensitivity indexes as well as to study the partition coefficients of phenols into ionic and nonionic micelles. The sensitivity indexes values can be used to estimate qualitatively the affinity between phenols and micelles. The studied phenols, some of them with high environmental interest, include chloro-, alkyl-, and methoxy-phenols. The results obtained in this work, using 85 microm polyacrylate fiber and anionic (sodium dodecyl sulphate), cationic (cetyltrimethylammonium bromide), and nonionic (Triton X-100 and polyoxyethylene-10-lauryl ether) surfactants, indicate that SPME is a viable method for estimating the micelle partition coefficients.

The screening of PAHs from seawater samples using cloud-point extraction (CPE) as a step prior to their determination by fluorescence measurements with a fiber-optic is proposed. The CPE is carried out with the nonionic surfactants mixture POLE and Brij 30. The fluorescence measurement parameters were optimized, allowing selection of benzo(a)pyrene (B(a)Py) and benzo(k)fluoranthene (B(k)Ft) as the target analytes for the screening. The reproducibility of the whole screening system, expressed as relative standard deviation, was 9.0% for B(a)Py and 12.1% for B(k)Ft (both for n = 7). The reliability of the method was established at five concentrations for B(a)Py (between 0.5 and 3.3 times the detection limit: 0.31 ng ml(-1)) and at three concentrations for B(k)Ft (between 0.6 and 2.5 times the detection limit: 0.56 ng ml(-1)). The resolution of binary mixtures of these PAHs at different levels of concentration, and a study of the interferences with the rest of the PAHs were also carried out.

In this work, the polycyclic aromatic hydrocarbons (PAHs) and their methyl derivatives concentrations have been determined in smoke from the rock rose and tree heather wood combustion. The combustion is done in two types of smokers, kiln and drum, commonly used in the Canary Islands (Spain) to smoke cheese. The low control of the operational conditions justify the great variability of the PAHs concentration in the emissions, with values between 251.8 and 2547 microg/m3N. In general, the lowest concentrations correspond to the tree heather wood combustion in the drum, while the highest concentrations are usually reached in the rock rose wood combustion in the kiln. However, the relative contributions of each PAH to the total concentration are independently similar to the type of smoker and wood used. In the combustion conditions, the equilibrium is not reached during the PAHs distribution process between the gas and aerosol phases. Therefore, while naphthalene and their 1- and 2-methyl derivatives remain in the gas phase, phenanthrene and PAHs with higher molecular weight remain mainly in the aerosol phase. In this phase, the PAHs concentration represents 39.9% of the total PAHs produced by burning rock rose wood and 29.1% of the total PAHs when tree heather wood is used. To establish the carcinogenic potential in both phases, the percentages of some PAHs were calculated. These values are significantly higher in the aerosol phase and, at the same time, higher when rock rose wood is used.

Solid-phase microextraction (SPME) coupled to gas chromatography with MS detection has been employed to study the partition coefficients of PAHs to ionic and nonionic micelles. The results obtained in this work for seven PAHs, using 85-microm polyacrylate- and 100-microm poly(dimethylsiloxane)-coated fibers and anionic (sodium dodecyl sulfate), cationic (cetyltrimethylammonium bromide), and nonionic (polyoxyethylene-10-lauryl ether) surfactants, indicate that SPME is a viable method for estimating the partition coefficients of PAHs to micelle. The procedure could also be potentially extended to the measurement of partition coefficients between a wide variety of semi- or nonvolatile compounds and micellar media.

Solid-phase microextraction (SPME) coupled with high-performance liquid chromatography (HPLC) with UV diode array detection (DAD) for the analysis of heterocyclic aromatic amines (HAs) is described. Four kinds of fiber coatings: Carbowax-templated resin (CW-TPR), Carbowax-divinylbenzene (CW-DVB), poly(dimethylsiloxane)-divinylbenzene (PDMS-DVB) and polyacrylate (PA) were evaluated for extraction of nine most biologically active heterocyclic aromatic amines. Different parameters affecting to the microextraction and determination of HAs were studied, such as absorption and desorption time, desorption mode, composition of the solvent for desorption, pH, ionic strength, and percentage of methanol in the sample. To determine these amines in food samples a new simplified procedure is proposed, consisting of treatment of the sample with methanolic NaOH prior microextraction by CW-TPR fiber coating and HPLC-DAD determination. The advantages of this new method are the reduced amounts of time and organic solvents required.

In this work, the nonionic surfactant polyoxyethylene-10-lauryl ether has been used for the extraction and preconcentration of 14 polycyclic aromatic hydrocarbons, classified as priority pollutants by the US Environmental Protection Agency, from seawater samples. The cloud-point preconcentration previous separation by HPLC and quantification using fluorimetric detection and wavelength programming allow to determine these pollutants with detection limits ranging from 1.0 to 1.5 x 10(2) ng/l with RSDs better than 10.4%. The methodology is evaluated using well-established extraction and preconcentration methods and GC-MS.

A fast microwave-assisted dansylation procedure has been developed for the derivatization of N-nitrosamines prior to high-performance liquid chromatography determination. N-Nitrosomorpholine, N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosopyrrolidine and N-nitrosopiperidine are first denitrosated by hydrobromic acid-acetic acid to produce secondary amines, which are then quantitatively dansylated in 5 min using radiation power of 378 W and a maximum pressure of 1.4 bar inside the reactor. The reaction mixture is separated on a C18 column with acetonitrile-water (55:45, v/v) as mobile phase with fluorimetric detection at 531 nm (excitation at 339 nm). The detection limits range from 8 to 75 pg for N-nitrosomorpholine and N-nitrosodiethylamine, respectively. The method was applied to study the recoveries of N-nitrosamines in beer and their determination in cigarette smoke.