Search

Liquid-liquid microextraction (LLME) techniques have experienced a tremendous growth over the last years but still face major challenges related to the use of more efficient and environmentally friendly solvents. Supramolecular solvents (SUPRASs) have proved outstanding efficiency in LLME, but many of the experimental conditions required for SUPRAS formation and/or application cannot be considered green or experimentally convenient. This paper was intended to make greener both SUPRAS formation and their application to the LLME of low-concentration organic pollutants in environmental waters. For this purpose, a variety of SUPRASs were produced at room temperature by simply mixing alkyl phosphonates (A

Permethrin (PM) is one of the chiral insecticides most widely used around the world. The significant differential toxicity of its four enantiomers and its important adverse effects on human health, highlights the need for determination of PM enantiomers. The aim of this work was to develop the first enantioselective method for quantification of PM in fruits and vegetables. The method is based on the extraction of PM enantiomers in a supramolecular solvent with restricted access properties (SUPRAS-RAM), and their separation/detection by chiral liquid chromatography-tandem mass spectrometry (LC-MS/MS), which is firstly reported in this article. SUPRAS-RAM-based extraction is proposed as an innovative treatment approach that drastically reduce solvent consumption and avoid the need for sample clean-up. Extraction of PM enantiomers is quick (vortexing for 5 min) and efficient (recoveries 93-107%). The method is sensitive (quantification limits from 1.0 to 1.2 µg kg-1) and suitable for control of PM enantiomers in agri-food products.

Methanetriyl-pi hydrogen bonding (CH-π HB) in nonpolar domains of supramolecular nanostructures is proposed here as a new mechanism to increase the extraction efficiency of aromatic compounds. The approach is illustrated by the extraction of priority carcinogenic polycyclic aromatic hydrocarbons (CPAHs) in soils using supramolecular nanostructures of carboxylic acids with nonpolar domains consisting of hydrocarbon chains (C6-C10) dispersed in tetrahydrofuran (THF). The high concentration of CH-groups available in the supramolecular nanostructures (38.7-47.3 M) enabled the efficient extraction of CPAHs (recoveries between 89 and 106%), using a supramolecular solvent (SUPRAS) volume/soil amount ratio of 1.5 µL mg

Halogen bonding (XB), a highly energetic and directional interaction, is here proposed as a new mechanism to increase solute solubilisation in solvent extractions. The approach is illustrated by the extraction of hexabromocyclododecane (HBCD) enantiomers in soils and sediments using supramolecular solvents (SUPRAS) containing XB donors in their structure. SUPRAS consisting of inverted hexagonal aggregates of decanoic acid, synthesized by water-induced coacervation of the amphiphile in tetrahydrofuran (THF), were explored for this purpose. Sample treatment involved the extraction of 400 mg of soil or sediment with 250 μL of SUPRAS for 5 min and then centrifugation for 10 min. SUPRAS extracts were directly analyzed by chiral liquid chromatography tandem mass spectrometry (LC-MS/MS) and quantification was carried out using isotopically labelled internal standards. Quantitative recoveries (93–102%) were obtained for the six HBCD enantiomers in both fresh and aged spiked samples. The mild experimental conditions required for extraction (room temperature and atmospheric pressure), the low SUPRAS volume/sample amount ratio needed (0.6 mL g─1), the short time required for sample treatment (15 min), and the simplicity of the procedure (use of conventional equipment and the possibility of treating several samples simultaneously), makes this method clearly superior to those previously reported. Method quantitation limits were in the intervals 0.58–2.23 ng g─1, and the relative standard deviations (n = 18, HBCD stereoisomer concentration = 50 ng g─1) obtained under repeatability and reproducibility conditions varied within the ranges 1.0–4% and 2.5–5%, respectively. The approach here described could be easily extended to the extraction of brominated flame retardants in different types of matrices.

Supramolecular solvents (SUPRASs) are nanostructured liquids produced by the self-assembly of amphiphiles at the molecular, nano and micro scale that offer excellent opportunities to be tailored through the bottom-up approach. They have a great potential for the setting-up of generalized sample treatments and multiresidue analysis due to their multi-binding capacity and tunability. Efficient extraction schemes can be developed thanks to the variety of interactions (dispersive, ionic, polar, etc.) they offer for solute solubilization. SUPRASs are simply synthesized by spontaneous processes and are considered as green alternatives to typical organic solvents (low toxicity, flammability, etc.). This review highlights those theoretical and practical aspects related to the synthesis and application of SUPRASs on which one should focus to exploit their benefits for the setting-up of efficient and reliable analytical schemes. It aims to provide a practical guide for SUPRAS selection and optimization in the analysis of organics by liquid chromatography (LC) separation and common LC detectors. Theoretical and operational aspects of SUPRAS are discussed with the aim of providing fundamental knowledge to potential users and facilitate implementation of SUPRAS-based methods in laboratories. Although the appealing power of self-assembly to give tailored SUPRASs remains largely unexplored, advances and opportunities regarding tailored SUPRAS are highlighted.

Halogen bonding (XB) was here proposed, for the first time, as a solubilization mechanism for increasing efficiency in the liquid-liquid microextraction of halogenated compounds. The approach was illustrated by the extraction of hexabromocyclododecane (HBCD) enantiomers in natural waters with a supramolecular solvent (SUPRAS) made up of inverted hexagonal aggregates of decanoic acid. The XB and dispersion interactions offered by the SUPRAS were able to extract the six HBCD enantiomers (i.e. (+)-α-, (-)-α- (+)-β-, (-)-β-, (+)-γ- and (-)-γ-) quantitatively (e.g. recoveries in the range 89–106%) and reach concentration factors as high as 720 without the need for solvent evaporation. HBCD enantiomers in the SUPRAS extract were directly analysed by chiral liquid chromatography coupled to tandem mass spectrometry (LC MS/MS). Quantitation limits of the method (0.09-0.9 ng L−1) were below the quality standard stablished by the European Union for HBCDs in inland surface water samples (1.6 ng L−1), and the precision, expressed as relative standard deviation (n = 6), was below 9% for all the HBCD enantiomers at concentrations within the range 50–500 ng L−1. The method was successfully applied to the enantioselective determination of HBCDs in the dissolved and the particle-bound fractions of river waters containing different concentration of suspended particles (10–57.8 mg L−1) that were spiked at two concentration levels (10 and 100 ng L−1). The results here obtained prove that XB is a valuable mechanism for the solubilisation of halogenated compounds that can effectively increase their recovery from liquid and solid samples.

This manuscript describes, for the first time, the simultaneous enantioselective determination of ibuprofen, naproxen and ketoprofen in wastewater based on liquid chromatography tandem mass spectrometry (LC–MS/MS). The method uses a single-step sample treatment based on microextraction with a supramolecular solvent made up of hexagonal inverted aggregates of decanoic acid, formed in situ in the wastewater sample through a spontaneous self-assembly process. Microextraction of profens was optimized and the analytical method validated. Isotopically labeled internal standards were used to compensate for both matrix interferences and recoveries. Apparent recoveries for the six enantiomers in influent and effluent wastewater samples were in the interval 97–103%. Low method detection limits (MDLs) were obtained (0.5–1.2 ng L–1) as a result of the high concentration factors achieved in the microextraction process (i.e. actual concentration factors 469–736). No analyte derivatization or evaporation of extracts, as it is required with GC–MS, was necessary. Relative standard deviations for enantiomers in wastewater were always below 8%. The method was applied to the determination of the concentrations and enantiomeric fractions of the targeted analytes in influents and effluents from three wastewater treatment plants. All the values found for profen enantiomers were consistent with those previously reported and confirmed again the suitability of using the enantiomeric fraction of ibuprofen as an indicator of the discharge of untreated or poorly treated wastewaters. Both the analytical and operational features of this method make it applicable to the assessment of the enantiomeric fate of profens in the environment.

A simple, sensitive, rapid and economic method was developed for the quantification of enantiomers of chiral pesticides as mecoprop (MCPP) and dichlorprop (DCPP) in soil samples using supramolecular solvent-based microextraction (SUSME) combined with liquid chromatography coupled to mass spectrometry (LC-MS/MS). SUSME has been described for the extraction of chiral pesticides in water, but this is firstly applied to soil samples. MCPP and DCPP are herbicides widely used in agriculture that have two enantiomeric forms (R- and S-) differing in environmental fate and toxicity. Therefore, it is essential to have analytical methods for monitoring individual DCPP and MCPP enantiomers in environmental samples. MCPP and DCPP were extracted in a supramolecular solvent (SUPRAS) made up of dodecanoic acid aggregates, the extract was dried under a nitrogen stream, the two herbicides dissolved in acetate buffer and the aqueous extract directly injected in the LC-MS/MS system. The recoveries obtained were independent of soil composition and age of herbicide residues. The detection and quantitation limits of the developed method for the determination of R- and S-MCPP and R- and S-DCPP in soils were 0.03 and 0.1 ng g(-1), respectively, and the precision, expressed as relative standard deviation (n=6), for enantiomer concentrations of 5 and 100 ng g(-1) were in the ranges 4.1-6.1% and 2.9-4.1%. Recoveries for soil samples spiked with enantiomer concentrations within the interval 5-180 ng g(-1) and enantiomeric ratios (ERs) of 1, 3 and 9, ranged between 93 and 104% with standard deviations of the percent recovery varying between 0.3% and 6.0%. Because the SUPRAS can solubilize analytes through different type of interactions (dispersion, dipole-dipole and hydrogen bonds), it could be used to extract a great variety of pesticides (including both polar and non-polar) in soils.

Supramolecular solvents (SUPRASs) are nanostructured liquids produced in colloidal solutions of amphiphilic compounds by spontaneous, sequential phenomena of self-assembly and coacervation. Unlike organic solvents and ionic liquids, SUPRAS components arrange in ordered structures that give them outstanding properties. Thus, they have regions of different polarities, offer mixed-mode mechanisms for solute solubilization, and have high concentration of amphiphiles, which render them very efficient extractants for solutes in a wide polarity range. Additionally, SUPRASs are nonvolatile and nonflammable, and the ordered structures can be tailored to meet specific functions by proper selection of amphiphiles and the environment. This chapter gives an overview of the main strategies developed for the synthesis of SUPRASs, the basic principles underlying their formation, the consequences of their reversibility for the design of tailored SUPRASs, and their main properties and applications.

Restricted access-volatile supramolecular solvents (RAM-VOL-SUPRAS) are here proposed as a new strategy for the quick removal of protein and phospholipids and efficient analyte extraction in LC-MS bioanalysis. Quantification of bisphenol A in urine was selected to prove the suitability of this approach for the intended purpose. RAM-VOL-SUPRAS were spontaneously synthesized in urine by addition of hexanol (83 μL) dissolved in THF (150 μL). SUPRAS composition was environment-dependent and an equation for prediction of SUPRAS volume under given experimental conditions was proposed. Urinary proteins were removed by flocculation by the combined action of THF and hexanol. Phospholipids were extracted in the SUPRAS by the formation of mixed aggregates with hexanol and precipitated as the SUPRAS extract (75 μL) was evaporated to dryness. BPA, re-extracted from the residue, was analysed by LC-(ESI)-MS/MS. Removal of phospholipids by precipitation was proved by monitoring them in both evaporated and unevaporated urine SUPRAS extracts by LC-MS. This removal led to significant reduction in matrix-effects in the determination of BPA. The method quantification limit in urine was 0.025 ng mL−1 and the repeatability for 0.4 ng mL−1 of BPA, expressed as relative standard deviation, was 4.5%. Concentrations of BPA in the urine samples analysed were in the range 0.357–1.58 ng mL−1. Recoveries were within the range 96–107%. This new approach for sample treatment in bioanalysis, based on the simplicity of dual precipitation of proteins and phospholipids, allows obtaining much cleaner extracts than conventional procedures.

A single-step, environmentally friendly sample treatment was developed and used in combination with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the quantitation of hexabromocyclododecane (HBCD) stereoisomers in fish. It was based on the microextraction of the stereoisomers with a supramolecular solvent (SUPRAS) made up of reverse aggregates of decanoic acid (DeA). The procedure involved the stirring of the fish sample (750 mg) with 600 μL of SUPRAS for five minutes, subsequent centrifugation for extract separation from matrix components and direct analysis of the extract after dilution 1:1 with methanol. Individual enantiomers of α-, β- and γ-HBCD were separated on a chiral stationary phase of β-cyclodextrin and quantified by monitoring of the [M-H](-)→Br(-) transition at m/z 640.9→80.9. Driving forces for the microextraction of HBCD in the SUPRAS involved both dispersion and dipole-dipole interactions. Quantitation limits for the determination of individual HBCD enantiomers in hake, cod, sole, panga, whiting and sea bass were within the intervals 0.5-3.4 ng g(-1), 0.9-2.5 ng g(-1), 0.6-1.4 ng g(-1), 1.0-5.6 ng g(-1), 0.8-1.3 ng g(-1) and 0.5-3.5 ng g(-1), respectively. Recoveries for fish samples fortified at the ng g(-1) level ranged between 87 and 114% with relative standard deviations from 1 to 10%. The sample treatment proposed greatly simplifies current procedures for extraction of HBCD stereoisomers and is a useful tool for the development of a large scale database for their presence in fish.

A multiresidue method was described for determining eight sulfonamides, SAs (sulfadiazine, sulfamerazine, sulfamethoxypyridazine, sulfachloropyridazine, sulfadoxine, sulfamethoxazole, sulfadimethoxine and sulfaquinoxaline) in animal muscle tissues (pork, chicken, turkey, lamb and beef) at concentrations below the maximum residue limit (100 μg kg(-1)) set by the European Commission. The method was based on the microextraction of SAs in 300-mg muscle samples with 1 mL of a supramolecular solvent made up of reverse micelles of decanoic acid (DeA) and posterior determination of SAs in the extract by LC/fluorescence detection, after in situ derivatization with fluorescamine. Recoveries were quantitative (98-109%) and matrix-independent, no concentration of the extracts was required, the microextraction took about 30 min and several samples could be simultaneously treated. Formation of multiple hydrogen bonds between the carboxylic groups of the solvent and the target SAs (hydrogen donor and acceptor sum between 9 and 11) were considered as the major forces driving microextraction. The method was validated according to the European Union regulation 2002/657/EC. Analytical performance in terms of linearity, selectivity, trueness, precision, stability of SAs, decision limit and detection capability were determined. Quantitation limits for the different SAs ranged between 12 μg kg(-1) and 44 μg kg(-1), they being nearly independent of matrix composition. Repeatability and reproducibility, expressed as relative standard deviation, were in the ranges 1.8-3.6% and 3.3-6.1%. The results of the validation process proved that the method is suitable for determining sulfonamide residues in surveillance programs.

The increasing pressure to decrease organic solvent usage in laboratories is fostering the search for alternative solvents. The liquid-liquid phase separation of surfactants, induced by environmental conditions, viz. temperature, electrolytes, pH, etc., has been largely used in analytical extraction and concentration schemes. The surfactant-rich phase is a nano-structured liquid, recently named as supramolecular solvent, generated from the amphiphiles through a sequential self-assembly process occurring on two scales, molecular and nano. This review covers progress on both theoretical and practical aspects related to the use of supramolecular solvents in analytical extractions reported over the last decade. Advances allowing a better understanding of the mechanisms of solvent production and solvent structure are outlined. Emphasis is then placed on solvent composition and its consequences on extraction efficiency, concentration factors and suitability for solubilising analytes over a wide range of polarities. Recent developments in formats and strategies making supramolecular solvents compatible with chromatographic and electrophoretic techniques along with a variety of detection systems are discussed. Applications of supramolecular solvents to the extraction of organic compounds mainly in the biological, environmental and agrifood areas are critically reviewed and main future trends outlined.

Sorbents made up of sodium dodecyl sulphate (SDS) hemimicelles, formed onto gamma-alumina, were proposed for the quantitative and practically solvent-free solid-phase extraction (SPE) of ibuprofen and naproxen from sewage samples. The formation of drug-SDS mixed aggregates was proved by the pseudophase separation model and their composition as a function of the amount of drug was calculated. The overall hemimicellar SPE procedure consumed only 0.6 mL of methanol since non-organic solvent was required for cartridge conditioning and the drugs were completely eluted using 2 mL of a 0.3M NaOH:methanol (70:30, v/v) solution. Breakthrough volumes of around 0.75 L and above 1L were obtained for naproxen and ibuprofen, respectively. No clean-up steps were necessary for the determination of these drugs in sewage because the direct analysis of the eluates by liquid chromatography/UV was matrix effect-free. The identification of the analytes was based on retention times and UV spectra and it was confirmed by on-line fluorescence detection. The detection limits for naproxen and ibuprofen were 0.8 and 9 ng L(-1) in wastewater influents and 0.5 and 7 ng L(-1) in effluents, respectively. These limits were similar to or lower than those achieved by methods based on conventional sorbents (e.g. C(18)-silica or polymeric resins), which invariably require the evaporation of the eluates. The accuracy and precision of the proposed method were assessed by analysing influent and effluent wastewater samples spiked with 2 and 0.4 microg L(-1) of each analyte, respectively. The recoveries obtained and the corresponding standard deviations were in the ranges 93-101% and 2-9%. The method was applied to the determination of the target drugs in wastewater from three sewage treatment plants (STPs) in the south of Spain. The concentration of ibuprofen and naproxen ranged between 2.0 and 7.4 microg L(-1) and 0.9 and 3.3 microg L(-1) in influents and 0.4 and 1.4 microg L(-1) and 0.2 and 0.8 microg L(-1) in effluents, respectively.

Sodium dodecyl sulphate (SDS)-coated alumina was used for the extraction/preconcentration of benzimidazolic pesticides (BFs) [carbendazim (CB), thiabendazole (TB) and fuberidazole (FB)] from river and underground water. SDS admicelles were required to get quantitative retention of BFs. Adsolubilization of analytes occurred through hydrophobic and electrostatic interactions. Methanol (1 ml) provided quantitative elution of the target analytes for all the samples analyzed. The high breakthrough volumes obtained (400 ml for CB and 1 l for BF and FB) and the low eluent volume used resulted in very high preconcentration factors (between 400 and 1000). Calcium was found to decrease BFs retention due to the disruption of SDS admicelles; however, this interference was easily removed by precipitation with SDS prior to BFs adsolubilization. The accuracy of the proposed method was assessed by studying recoveries of BFs in natural waters at two spiking concentration levels (80, 40 and 4 ng l −1 , and 400, 200 and 20 ng l −1 for CB, TB and FB, respectively); mean recoveries in the intervals 96–105% and 98–108% were obtained for river and underground water samples, respectively.

An aggregation parameter-based methodology for determining acid and neutral drugs in pharmaceutical dosage forms is presented. The method is based on competitive self-assembly in ternary dye-surfactant-drug aqueous mixtures. Dyes bearing charge of opposite sign to that of surfactants bind to surfactant to form mixed dye-surfactant aggregates, which are monitored from changes in the spectra features of the dye. The drug competes with the dye to interact with the surfactant to form drug-surfactant aggregates, which results in a decrease in the surfactant to dye binding degree proportional to the drug concentration in the aqueous solution. Coomassie Brilliant Blue G (CBBG) and didodecyldimethylammonium bromide (DDABr) were the dye and surfactant reactant used, respectively. The suitability of the surfactant to dye binding degree (SDBD) method to determine drugs with very different molecular structure: propionic (flurbiprofen, ibuprofen, naproxen and ketoprofen) and acetic (diclofenac, felbinac and zomepirac) acids, indolines (indomethacin and sulindac), glycyrrhetinic acid derivatives (carbenoxolone and enoxolone), salicylates (diflunisal and phenyl salicylate), oxicams (meloxicam, piroxicam and tenoxicam), pyrazolones (phenylbutazone and sulfinpyrazone) and hydrocortisones (dexamethasone and prednisolone) has been proved. The proposed method was successfully applied to the determination of drugs in commercial formulates (effervescent granulates, tablets, suppositories, gels and blisters) with a minimum sample treatment (dilution of liquid samples and dissolution of solid samples).

The determination of fusidic acid (FA)/sodium fusidate (SF) in dosage forms based on their modification of the binding degree of the cationic surfactant didodecyldimethylammonium bromide (DDABr) to the anionic dye Coomassie Brilliant Blue G (CBBG) was proposed. The formation of mixed DDABr–CBBG aggregates was monitored from changes in the spectral features of the dye. Addition of fusidane antibiotic to DDABr–CBBG aqueous mixtures caused a decrease in the surfactant–dye binding degree as a result of the formation of DDABr–drug aggregates. At the working pH (7.0), FA and SF were as fusidate anion; therefore, both hydrophobic and attractive electrostatic interactions were responsible for the formation of these mixed surfactant–drug aggregates. Based on the mathematical expression previously derived for determining surfactants, a linear calibration in the fusidane antibiotic concentration range 1.9–70 mg L−1 was obtained. The surfactant to dye binding degree (SDBD) method offered important advantages over conventional method used for quality control of fusidane antibiotics in terms of sensitivity (detection limit = 0.6 mg L−1), selectivity, which permitted a minimum sample treatment (only dissolution of dosage forms), precision [relative standard deviations for the whole analytical process = 1.5–2.0% (n = 6)], rapidity, because of the speed of both sample treatment and determination step, required instrumentation (a photometric titrator) and cost. Pharmaceutical samples analyzed included tablets, pomades and creams.

The surfactant–dye binding degree (SDBD) method was extended to the determination of amphiphilic drugs. This new methodology was based on the effect of amphiphilic compounds on the degree of binding of a surfactant to dye molecules. The dye induces the formation of surfactant aggregates and allows this process to be monitored from changes in their spectral features. The interaction between the anionic dye Coomassie Brilliant Blue G (CBBG) and the cationic surfactant didodecyldimethylammonium bromide (DDABr) was used for the sensitive determination of phenamic acids (meclophenamic, mephenamic, fluphenamic and niflumic acid), non-steroidal anti-inflammatory drugs. The addition of phenamic acid to the dye–surfactant mixture resulted in the formation of drug–DDABr aggregates with well-defined stoichiometries (between 1:1 and 1:3) and, hence, in decreased interactions between the dye and the cationic surfactant. Mixtures of drug–surfactant were demonstrated to behave as those made up of pure surfactant, and, therefore, the expression previously derived for determining surfactants could be used to quantify amphiphilic drugs. The proposed method permitted the determination of phenamic acids at the mg l−1 level with the precision required for quality control (the relative standard deviation for 7 mg l−1 of meclophenamic acid was 1.1%). Pharmaceutical preparations were analysed directly after dissolution of the samples in ethanol.

A new analytical measurement parameter based on the effect of amphiphilic substances on the degree of binding of a surfactant to dye molecules, which induce the formation of surfactant premicellar aggregates, is presented. The theory for dye-surfactant intermolecular interactions in mixed surfactant systems, which assumes a mononuclear model for the formation of dye-induced premicellar aggregates, has been used to derive an expression that provides linear calibrations for the determination of amphiphilic compounds. The dye-surfactant interactions involved have been investigated, and the variables affecting the measurement analytical parameter have been discussed. The analytical applicability of the surfactant-dye binding degree method is demonstrated by quantifying major anionic surfactants at the nanograms-per-milliliter level and determining the total concentration of these amphiphilic substances in sewage samples (average recoveries ranged from 98 to 102%).

On the basis of a better analytical exploitation of acid-induced cloud point approach, a systematic study on the phase behaviour of acid aqueous solutions of anionic surfactants and factors affecting anionic surfactant-mediated extractions was performed. The anionic surfactants investigated were alkylsulphonates (ASS) with alkylchain lengths comprised between 8 and 16 carbon atoms. The critical hydrochloric acid concentration (minimal acid concentration required to separation in two liquid phases) was found to increase as alkylchain length of the anionic surfactant increased from 10 to 14. Non-acid-induced liquid–liquid phase separation was observed for sodium octanesulphonate (SOS) or sodium hexadecyl sulphonate (SHS) in the hydrochloric concentration range 0–10 M. Acid aqueous solutions of sodium decylsulphonate (SDeS) and sodium dodecylsulphonate (SDoS) separated into two liquid phases at temperatures ranging between 10 and 80 °C, while temperatures >35 °C were required for sodium tetradecylsulphonate. The influence on extraction efficiency and concentrating ability of experimental variables such as hydrophobicity and concentration of surfactant, nature and concentration of analyte, hydrochloric acid concentration, time and temperature of extraction and time of equilibration and centrifugation was examined. Advantages provided by anionic surfactant-mediated extractions over the use of non-ionic surfactants (cloud point extractions) are discussed.

Toxicity of pharmaceuticals to aquatic biota is still largely unknown, and no research on the stereoselective toxicity of chiral drugs to these organisms has been undertaken to date. Because of the lack of analytical methods available for this purpose, this manuscript deals, for the first time, with the enantioselective analysis of the non-steroidal anti-inflammatory drugs (NSAIDs) ibuprofen, naproxen and ketoprofen in freshwater fish. The method was based on the microextraction of NSAIDs from fish muscle with a supramolecular liquid made up of inverted hexagonal aggregates of decanoic acid, their enantiomeric separation by liquid chromatography onto a (R)-1-naphthylglycine and 3,5-dinitrobenzoic acid stationary phase and quantification by tandem mass spectrometry. Limits of quantitation (LOQs) for NSAID enantiomers were in the range 1.7-3.3 ng g(-1). Absolute recoveries were from 97 to 104 %, which indicated the high extraction efficiency of the supramolecular solvent. Extraction equilibrium conditions were reached after 10 min which permitted fast sample treatment. Relative standard deviations for enantiomers in fish muscle were always below 6 %. Isotopically labelled internal standards were used to compensate for matrix interferences. The method in-house validation was carried out with the Oncorhynchus mykiss species, and it was applied to the determination of NSAID enantiomers in different fortified freshwater fish species (Alburnus alburnus, Lepomis gibbosus, Micropterus salmoides, O. mykiss and Cyprinus carpio).

Supramolecular solvents (SUPRASs) have been long recognized as outstanding extractants in analytical processes. In addition to their remarkable properties for solubilization of a number of polar and apolar compounds using minute volumes of solvent, they can be tailored at will and produced spontaneously at reduced cost. Although not enough effort has been devoted to the synthesis of new solvents and elucidation of their structure, important progress has been performed in the past decade to the development of new formats and the coupling to different detection systems. This article gives an overview of the state of art of how solvents are produced, their capability for extraction and concentration, the formats used, the strategies developed to make SUPRASs compatible with a number of detection systems, and major applications reported on the extraction of metals and organic compounds in the biological, environmental, and agrifood areas.

The use of the mixed aggregate method for the determination of amphiphilic substances is considered. The principles that support this method are presented, and the strategies devised so far for increasing sensitivity, selectivity and precision are discussed on the basis of both the theoretical background and the applications developed. The usefulness of this new approach in environmental and pharmaceutical applications is documented.

Many aromatic compounds are oxidized but not completely mineralized by Fenton’s reagent. Little attention has so far been given to the identification of residual organic matter and the evaluation of its toxicity. In this work, the oxidation of metol [ N -methyl- p -aminophenol] by Fe 2+ /H 2 O 2 in the dark as a model for aromatic amines and alcohols was examined. Analysis of oxidized solutions was performed by both LC-electron impact (EI)-MS and LC-electrospray ionization (ESI)-MS. It was checked that the degradation of metol takes place via direct oxidation by Fe 3+ and OH attack. Intermediates amenable to oxidation by OH are basically partially oxygenated aromatic species, dimerization products and polymers. End products not amenable to oxidation by this radical are ferrycarboxylate complexes, which are non-toxic to UC581 bacterial cells. These complexes can be completely destroyed by irradiation with light. The photo-Fenton reaction is therefore an effective choice for the in situ treatment of industrial effluents containing aromatic amines and hydroxylated species.

The potential of the Fenton’s reagent for oxidation of p -aminophenols, which are the main developers used in white and black processes, was assessed. Metol [ N -methyl- p -aminophenol] was chosen as a model. Degradation of this compound by Fenton’s reagent was examined under dark conditions as a function of reagent concentrations and pH used in batch treatments. Under optimal conditions, 0.2 M H 2 O 2 , 9.0×10 −4 M Fe 2+ , pH 3–5 and room temperature, the initial COD of a 5×10 −3 M metol solution was reduced by about 50% within 2 h. After this time, additional COD reduction was very slow (about 20% in five days). No aromatic compounds were detected about 4 h of reaction indicating that residual organic matter was mainly made up of ring cleavage products. Metol conversion behaved as a first-order reaction with respect to metol and Fe 2+ . Complete destruction of residual organic matter could be achieved at high temperatures (about 60°C) or by using the photo-Fenton reaction, which thus opens up prospects for an effective treatment of p -aminophenols in effluents from photographic processes.

The acid-induced liquid−liquid phase separation of anionic surfactants in aqueous solutions, and its applicability to cloud point extraction methodology, were examined. The phase diagrams obtained (e.g., [HCl] vs [surfactant]) consisted of three regions: a homogeneous liquid region, two coexisting isotropic phases, and a solid region. The breadth of each region was found to depend on the surfactant structure. The behavior of each phase was also examined in relation to temperature and added salts. The anionic surfactants investigated were sodium dodecyl sulfate (SDS), sodium dodecylbenzenesulfonic acid (SDBSA), sodium dodecanesulfonic acid (SDSA), and sodium dioctylsulfosuccinate (Aerosol OT). The use of anionic surfactant-mediated phase separations provided very high extraction efficiencies (80−100%) for pyrene in aqueous samples and various PAHs in a certified reference material (dried sewage sludge). The preconcentration factor achieved was found to be a function of both surfactant and acid concentrati...

Anionic surfactants separate into two isotropic phases in an acid medium at room temperature and can be successfully used in the cloud point extraction methodology. In this work, the anionic surfactant sodium dodecane sulphonic acid (SDSA) has been used for the extraction and preconcentration of the 16 polycyclic aromatic hydrocarbons (PAHs) classified as priority pollutants by the EPA from water samples (network supply, underground and river). Subsequent separation by HPLC and quantification using fluorimetric detection and wavelength programming has allowed these pollutants to be determined with detection limits from nanograms to subnanograms per litre. The use of SDSA offered two significant advantages about the nonionic surfactants generally utilized in the cloud point methodology for extraction of PAHs, namely, low fluorescence and absorbance signals at the PAHs detection wavelengths (because of the absence of an aromatic moiety in the surfactant molecule), and a low chromatographic retention time (owing to the polar character of SDSA). These features allowed the sensitive determination of the more polar PAHs without the need of a clean-up step to remove the surfactant. Negligible sorption of PAHs onto the containers when SDSA is added as a stabilizing agent, desorption of these pollutants if the sample has been collected without preservation and high recoveries, even in the presence of considerable levels of humic acids, were other features found for the proposed SDSA micelle mediated extraction of PAHs.

The determination of dialkyldimethylammonium surfactants (DDAS) based on the measurement of the critical micelle concentration (CMC) of mixed sodium dodecylsulphate (SDS)-DDAS aggregates in a basic medium ([NaOH]=4.8 × 10−3 M) is proposed. The dye Coomassie Brilliant Blue G (CBBG) was used as a photometric probe for the rapid determination of CMCs. Formation of CBBG-DDAS and DDAS-SDS premicellar aggregates of well-defined stoichiometrics at cationic and anionic surfactant concentrations far below their CMCs is demonstrated. Increased SDS concentration in the titration medium results in the formation of DDAS-SDS mixed micelles. The strong interaction between the opposite charged head group of DDAS and SDS permits these cationic surfactants to be determined at the ng ml−1 level with a nearly uniform response for all the DDAS tested (12–18 alkyl carbons). The relative standard deviation for 1.10 μg ml−1 ditetradecyldimethylammonium bromide (DTDAB) was 1.5%. The mixed-micelle based methodology was ap...

A new approach to the determination of polysorbates (PSs) in foods based on measurements of the critical micelle concentration of mixed micelles is proposed. PSs in a 0.25 M sulfuric acid medium are titrated photometrically with Triton X-100. The dye Coomassie brilliant blue G (CBBG) is used as a photometric probe for the rapid determination of critical micelle concentration values. The detection limits achieved for the PSs studied (viz. PS 20, PS 40, PS 60, PS 65 and PS 80) ranged from 0.05 to 0.08 μM. The relative standard deviation for 0.3 μM PS 60 was 2.8%. Food samples can be analyzed directly after dissolving PS from foodstuffs (baked bread, doughnuts, biscuits, butter, margarine, chocolate and noodle soup) with distilled water at room temperature. Average recoveries ranged from 98.0 to 99.3%.

Mixtures of anionic and cationic surfactants that form aggregates of pseudo-nonionic character and single-phase micellar solutions in the anionic- or cationic-rich range, were used to develop an effective approach to the determination of ionic amphiphilic substances based on the mixed-micelle methodology. Various alkyltrimethylammonium surfactants (ATAS) and sodium dodecyl sulphate (SDS) were tested as analytes and titrant, respectively. Nonionic–cationic aggregates made up of Triton X-100 and ATAS were comparatively studied. The linear concentration range achieved for ATAS based on the formation of pseudo-nonionic complexes was 0.1–0.6 μM, which permits these surfactants to be determined more sensitively than with both nonionic–cationic aggregates and monomer-based methods. Because of the opposite charge of the surfactants forming the pseudo-nonionic aggregates, strong synergism effects were observed for these systems. As a result, the critical micelle concentration for the mixture was significantly lower than those for the anionic and cationic surfactants alone, improving thus the detection limit for ATAS. The response was independent of the length of the hydrophobic chain in the cationic surfactant as the likely result of electrostatic interactions governing the incorporation of ATAS into SDS micelles. The relative standard deviation within- and between-assays for 0.3 μM of dodecyltrimethylammonium bromide was 3.3% and 3.9%, respectively.

A new hydrogen cyanide collecting device based on the use of borosilicated micro-fibreglass filters impregnated with sodium hydroxide was proposed and its performance assessed. It was used for the determination of hydrogen cyanide in air by a kinetic-fluorimetric method within the 5–600 ng ml–1 range. The proposed method is based on the catalytic effect of cyanide on the oxidation of pyridoxal-5′-phosphate (PALP) by dissolved oxygen in the cationic micellar medium afforded by dodecyltrimethylammonium bromide (DTAB). The reaction was monitored by measuring the fluorescence of the oxidation product [4-pyridoxic acid 5-phosphate (PAP)]. The improved sensitivity provided by DTAB micelles was due to an increase in the quantum yield of PAP when it was concentrated on the DTAB micellar surface, resulting in an apparently increased reaction rate. The relative standard deviation for 50 ng ml–1 of cyanide was 1.7%. Common interferences, such as those arising from carbon dioxide, nitrogen oxides (NOx) and sulfur oxides (SOx), were found not to affect the hydrogen cyanide determination. The interference from hydrogen sulfide could be detected (e.g. the kinetic curve recorded showed an induction period) and amended.

The potential of the oxidation of various carcinogenic aromatic amines by Fenton's reagent [Fe(II) + H2O2] for liquid waste treatments was assessed. The insoluble products yielded were amenable to oxidation to ring-cleavage products and ultimately to carbon dioxide. Mineralization was confirmed by mass spectrometry. The kinetics of precipitation was determined from scattering measurements, at 500 nm, of the insoluble substance produced as a function of time. The influence of experimental variables on the removal of aromatic amines from aqueous solutions by formation of insoluble products and ring-cleavage products was established. Complete removal took about 1 and 3 h of treatment overall for the formation of insoluble products and ring-cleavage products, respectively. Residual hydrogen peroxide, iron(II) concentration, chemical oxygen demand and chromatographic techniques were used to determine when the reaction was finished. The iron(II) concentration was found to be crucial to the nature of the end products obtained (insoluble products, ring-cleavage products, CO2).

Application of mixed micelle-based methodology was extended to the determination of C 10 –C 16 alkyl sulphate surfactants which have critical micelle concentrations (cmc) in the range 10 −12 –10 −4 M. The cmc is decreased by about two or three orders of magnitude by the presence of sodium chloride (2.2 M) and hydrochloric acid (0.7 M) in the titration medium, which permits these surfactants to be determined at the same concentration levels as with monomer-based methods. The sensitivity of mixed micelle-based methodology is shown to depend on both the cmc of the analyte and its value relative to the cmc of the titrant. The linear concentration range achieved for alkyl sulphate surfactants is 0.05–2 mg l −1 . Responses are independent of the molecular weight for surfactants containing more than 10 carbon atoms in the alkyl chain. A selectivity study revealed that no inorganic ions (e.g. Cl − , SO 4 2− , NO 3 − , Ca 2+ , Mg 2+ , Fe 3+ , etc.) interfere because their electrolyte effect is insignificant due to the high concentration of added salts. Dissolved organic compounds such as fenol, aniline and o -dianisidine are also tolerated at high concentrations because of the little effect of solubilization on micellization. Additional advantages of mixed micelle-based methodology over most analytical methods using monomeric anionic surfactants include experimental convenience (no extraction is needed in the determination step) and expeditiousness (mixed micelles are formed instantaneously).

A method for the simultaneous kinetic determination of pyridoxal (PAL) and pyridoxal-5′-phosphate (PALP) based on their cyanide-catalyzed aerobic oxidation in the presence of cetyltrimethylammonium bromide (CTAB) micelles is developed. The fluorescent reaction products yielded from PAL-cyanide and PALP-cyanide reactions [4-pyridoxolactone (PL) and 4-pyridoxic acid 5-phosphate (PAP), respectively] concentrate on the CTAB micellar surface and this ‘local concentration’ effect increases their quantum yield which results in apparently increased reaction rates. Because of the different partition or ‘binding’ constants of PL and PAP to CTAB ( K PL = 50 ± 6 M −1 and K PAP = 1390 ± 10M −1 ), this micellar medium accelerates PAL-cyanide and PALP-cyanide systems in a different extent leading to the kinetic discrimination of both vitamers. PAL and PALP are determinated simultaneously over the concentration range 1 × 10 −8 − 6 × 10 −7 M with relative errors less than about 5%. The role of CTAB micelles on the studied systems is discussed.

A new approach to the determination of surfactants is proposed, based on the formation of mixed micelles from binary surfactant solutions, one of the surfactants being the analyte. The theory for nonideal mixed micelles, according to itch the critical micelle concentration of mixed systems depends on the solution composition, was used to derive an expression that provides linear calibrations for the determination of surfactants. The hypothesis put forward for the analytical applicability of the proposed expression is experimentally veiled. The analytical applicability of this methodology is demonstrated by quantitating major nonionic alkoxylated surfactants; the linear surfactant concentration range achieved was from 0.2 to 4 mg L -1 . The main advantages of the proposed methodology over most analytical methods using monomeric nonionic surfactants include responses that are not dependent on the molecular weight or on the ethylene oxide units in the alkokylated surfactant, experimental convenience (no extraction or precipitation of the product formed in the determinative step is required), and rapidity (mixed micelles are formed instantaneously). The methodology can be extended to the determination of all types of surfactants in aqueous and organic media

A kinetic-photometric method for the determination of the anionic surfactant sodium dodecyl sulphate (SDS) is proposed. The method is based on the accelerating effect of micelles of the surfactant on the reaction between iron(II) and 1,10-phenanthroline, which is monitored via the ferroin complex formed. While Triton X-100 micelles have no catalytic effect on the reaction, this non-ionic surfactant forms mixed micelles with SDS, thereby considerably reducing the anionic surfactant concentration at which catalysis of the complex formation reaction starts. SDS was determined over the range 50–400 μg ml (detection limit 15 μg ml ) with a relative standard deviation of 3% for 200 μg ml . The proposed method was applied to the direct determination of the surfactant in pharmaceuticals (three shampoos, a toothpaste and a rectal solution) with satisfactory results. The main advantages of using micellar catalysis instead of monomer properties for the determination of the surfactant include enhanced selectivity and experimental convenience (use of organic solvents is avoided), whereas its most serious disadvantage is the increased detection limit of the micellar catalysis method.

Premicellar aggregates of the cationic surfactants cetylpyridinium chloride (CPC) enhance the catalytic activity of iron(III) on the oxidation of sulphanilic acid by potassium periodate in the presence of 1,10-phenanthroline as activator. The aggregates however have no effect on the uncatalysed reaction. The kinetic study presented in this paper shows that the effects of CPC on the iron(III)-catalysed reaction can be entirely attributed to increased reactant concentrations in the surfactant micelle subunits. The iron(III) effective concentration in the reaction medium is increased by formation of a transient catalyst-sulphanilic acid complex in the catalytic cycle which concentrates on the premicellar aggregates. Such an effect of CPC was exploited for the kinetic photometric determination of iron(III) over the linear range 0.1–4.0 × 10−7 M with a detection limit of 3.37 × 10−9 M. (i.e., 7 times lower than that of the method using an aqueous medium). The relative precision for 2.0 × 10−7 M of iron(III) was 5%. The proposed method is highly sensitive and selective and was applied to the determination of iron in blood serum samples.

Development of simple and rapid analytical methods for predicting supplemental feeding requirements in aquaculture is a need to reduce production costs. In this article, a supramolecular solvent (SUPRAS) made up of decanoic acid (DeA) assemblies was proposed to simplify sample treatment in the total and individual determination of carotenoids (red-pink pigments) in farmed salmonids. The analytes were quantitatively extracted in a single step that spends a few minutes using a small volume of SUPRAS (i.e. 800 μL) and directly determined in extracts without the interference from fats or other matrix components. The methods based on the combination of microextraction with SUPRAS and photometry or HPLC-UV/VIS spectroscopy were developed for the determination of total and individual carotenoids, respectively. The applicability of the methods was demonstrated by analysing non-fortified and fortified samples of farmed Atlantic salmons and rainbow trouts. Recoveries obtained by photometry and HPLC-UV/VIS spectroscopy were within the intervals 98-104% and 94-106%, respectively.

Solvents used in microextraction require high solubilising capability to efficiently extract the target compounds. In this article, nanostructured solvents made up of alkyl carboxylic acids (ACAs) aggregate are proposed for the efficient microextraction of acidic pesticides from natural waters. The target compounds were chlorophenoxy acid herbicides (CPAHs) widely used in agriculture, forestry and gardening (viz. 2,4-D, MCPA, MCPP, 2,4,5-T and MCPB). The supramolecular solvents (SUPRASs) tested were generated from solutions of reverse micelles of octanoic (OcA), decanoic (DeA) and dodecanoic (DoA) acid in THF by the addition of water, which acted as the coacervating agent. The DeA-based SUPRAS was the most efficient extractant for CPAHs; actual concentration factors (ACFs) of 260 for 2,4-D, 290 for MCPA, and 400 for MCPP, 2,4,5-T and MCPB were obtained. The explanation for so high ACFs can be found in the extremely efficient retention mechanisms that the DeA-based SUPRAS provides for CPAHs (i.e. formation of hydrogen bonds and hydrophobic interactions), and the high number of binding sites that it contains (i.e. the concentration of biosurfactant in the SUPRAS was 0.56 mg μL(-1)). Both characteristics permitted to effectively extract the target analytes in a low volume of solvent (about 2 μL of solvent per mL of sample). Others assets of the proposed supramolecular solvent-based microextraction (SUSME) approach included recoveries no dependent on matrix composition, rapidity (sample treatment spent about 15 min), use of low volume of sample (63 mL per analysis) and simplicity (no special lab equipments was needed). Combination with liquid chromatography/ion-trap mass spectrometry [LC-(IT)MS] afforded method quantitation limits for CPAHs within the interval 22-30 ng L(-1). The precision of the method, expressed as relative standard deviation (n=11, [CPAH]=200 ng L(-1)), was in the range 2.9-5.8%. The applicability of the method to the analysis of natural waters was assessed by determining the target analytes in fortified river and underground water samples.

The complexation kinetics and equilibrium of the reactions of vanadium(V) and titanium(IV) with Pyrogaliol Red (PGR), and the kinetics of oxidation of chromium(VI) by PGR were studied in micellar solutions of dodecyltrimethylammonium bromide (DTAB). The 1:1 PGR-V(V) and 2:1 PGR-Ti(IV) complexes formed in an aqueous medium associate with DTAB molecules of the micellar system to yield the new complexes 1:1:2 PGR-V(WDTAB and 2:1:1 PGR-Ti(IV)-DTAB. The stability constants of the ternary complexes were calculated by considering the volume fraction of micelles and were compared with those determined from the overall solution volume. The binding constants for the associates of PGR, chromium(VI), vanadium(V), titanium(IV), PGR-V(V) and PGR-Ti(IV) complexes with DTAB micelles were spectrophotometrtcally determined. The observed rate of formation of the PGR-Ti(IV) complex was increased by the presence of DTAB micelles, but the second-order rate constant in the micellar pseudo-phase was slightly lower than in water. Therefore, the whole rate increase observed was due to the concentration of reactants in the micellar pseudo-phase. The kinetics of formation of the PGR-V(V) complex could not be investigated by using the stopped-flow technique because the reaction was too fast in both the aqueous and the micellar medium. The second-order rate constant for the oxidation reaction between PGR and Cr(VI) was found to exceed that in aqueous solutions by a factor of ca. 55. Therefore, the increased rate observed for this reaction in the DTAB micellar medium can be ascribed to intrinsic effects of the micellar pseudo-phase on reactivity.

Application of the kinetic Wavelength-pair method was extended to the fixed-time kinetic variant with the simultaneous determination of arsenate and phosphate based on the formation of a heteropoly acid with molybdate and subsequent reduction with ascorbic acid to molybdenum blue compounds with strongly overlapping spectra. Resolution of the mixture by using discrete wavelengths was impossible. Selectivity in the resolution was achived by measuring the absorbance difference at the wavelength pair 820-740 nm and a fixed time of 100 s, where the contribution of phosphate was greatly decreased. Arsenate and phospate were simultaneously determined in weight ratios between 5:1 and 0.3:1 at concentrations from 0.5 to 6 μg ml −1 , with relative standard deviations between 3% and 5% for arsenate and between 1.5% and 2.5% for phosphate. The theoretical basis adapted to first-order kinetic-based determinations was established.

A simultaneous kinetic resolution of binary mixtures of cyanide, sulfide, and sulfite by reaction with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) in aqueous cetyltrimethylammonium bromide (CTAB) micelles was developed. The use of micelles increased the rate constants of the three reactions involved to a different extent and this differential behavior permitted the simultaneous kinetic analysis of mixtures of the anions by using appropriate surfactant concentrations. The determination of binary mixtures of cyanide, sulfide, and sulfite over the concentration ranges (0.6-1.5) ×10 -4 , (0.2-1)×10 -4 , and (0.2-1.5)×10 -4 M, respectively, was accomplished with relative errors less than 5%

Supramolecular analytical chemistry is an emergent science covering the study and application of supramolecular systems (host molecules and molecular aggregates) in analytical processes. This article covers the progress on both theoretical and practical aspects related to the use of supramolecular systems in separation techniques reported over the last decade. Principles of supramolecular chemistry that allow a better understanding of the mechanisms of formation of the supramolecular entities and solubilization of solutes are outlined. Developments related to the use of supramolecular solvents and hemimicellar or admicellar sorbents in analytical extractions are critically discussed. Advances in the use of micelles in liquid chromatography (LC) and electrophoresis as well as developments in chiral chromatography and electrophoresis based on the use of cyclodextrins (CDs) and their derivatives are presented. Emphasis is placed on the strategies developed to make these techniques compatible with mass spectrometry (MS). The capability of supramolecular systems to effectively solubilize solutes in a wide polarity range is highlighted. Keywords: supramolecular analytical chemistry; liquid chromatography; gas chromatography; capillary electrophoresis; cyclodextrins; supramolecular solvents; hemimicelles/admicelles

The cationic surfactant dodecyltrimethylammonium bromide (DTAB) enhances the catalytic of lead(II) on the oxidation of Pyrogallol Red (PR) by peroxodisulphate. Lead(II) accelerates this reaction by forming a complex with PR which concentrates on the micellar surface. The micellar catalysis of DTAB was used for the kinetic spectrophotometric determination of lead(II) over the range 2–18 ng ml −1 (detection limit 1.3 ng ml −1 ), the relative precision for 10 ng ml −1 of lead(II) being 3%. The proposed method is highly selective and its analytical features are clearly superior to those of its counterpart involving an aqueous medium. The mechanism via which DTAB acts on the reaction was studied in depth.

An indirect kinetic-photometric method for the determination of As(III) over the range 7–300 ng ml−1 is proposed. It is based on the accelerating effect of this ion on the Os(VIII)-catalysed reaction between iodide and bromate, which is monitored via the triiodide formed. Arsenic(III) acts as an accelerator only in a very rapid initial step of the reaction and the rate processes occurring in the system after this step do not depend directly on the As(III) concentration. Therefore, the contribution of this ion to the reaction must be measured after its accelerating effect has cancelled. Dodecyltrimethyl-ammonium bromide (DTAB) micelles accelerate the reaction, and hence increase the sensitivity and selectivity of the determination of As(III) compared to reactions taking place in an aqueous medium. Some observations on the mechanism via which DTAB acts on the reaction are reported. The role of micellar media in catalytic kinetic methods is discussed.

Supramolecular solvents are here proposed firstly as extractants in solid sample microextractions. The approach was evaluated by extracting flumequine (FLU) and oxolinic acid (OXO), two widely used veterinary medicines, from fish and shellfish muscle using a supramolecular solvent made up of decanoic acid (DeA) reverse micelles. The antibiotics were extracted in a single step (approximately 15 min), at room temperature, using 400 microL of solvent. After centrifugation, an aliquot of the extract was directly analyzed by liquid chromatography and fluorescence, without the need of clean-up or solvent evaporation. Contrary to the previously reported methods, both OXO and FLU were quantitatively extracted from fish and shellfish, independently of sample composition. The high extraction efficiencies observed for these antibiotics were a consequence of their amphiphilic character which resulted in the formation of DeA-OXO and DeA-FLU mixed aggregates. The quality parameters of this quantitative method including sensitivity, linearity, selectivity, repeatability, trueness, ruggedness, stability, decision limit and detection capability were evaluated according to the 2002/657/EC Commission Decision. Quantitation limits in the different samples analyzed (salmon, sea trout, sea bass, gilt-head bream, megrim and prawns) ranged between 6.5 and 22 microg kg(-1) for OXO and, 5 and 15 microg kg(-1) for FLU. These limits were far below the current maximum residue limits (MRLs) set by the European Union (EU) (i.e. 100 and 600 microg kg(-1), for OXO and FLU, respectively). The trueness of the method was determined by analyzing a Certified Reference Material (CMR, BCR-725) consisting of a lyophilised salmon tissue material. Recoveries for fortified samples (50-100 microg kg(-1) of OXO and 50-600 microg kg(-1) of FLU) and their relative standard deviations were in the intervals 99-102% and 0.2-5%, respectively. The repeatability, expressed as relative standard deviation, was 3.6% for OXO and 2.3% for FLU ([OXO]=[FLU]=200 microg kg(-1) and n=11).

A supramolecular solvent consisting of vesicles, made up of equimolecular amounts of decanoic acid (DeA) and tetrabutylammonium decanoate (Bu4NDe), dispersed in a continuous aqueous phase, is proposed for the extraction of benzimidazolic fungicides (BFs) from fruits and vegetables. Carbendazim (CB), thiabendazole (TB) and fuberidazole (FB) were extracted in a single step and no clean-up or concentration of extracts was needed. The high extraction efficiency obtained for BFs was a result of the different types of interactions provided by the supramolecular solvent (e.g. hydrophobic and hydrogen bonds) and the high number of solubilisation sites it contains. Besides simple and efficient, the proposed extraction approach was rapid, low-cost, environment friendly and it was implemented using conventional lab equipments. The target analytes were determined in the supramolecular extract by LC/fluorescence detection. They were separated in a Kromasil C18 (5 microm, 150 mm x 4.6 mm) column using isocratic elution [mobile phase: 60:40 (v/v) 50 mM phosphate buffer (pH 4)/methanol] and quantified at 286/320 nm (CB) and 300/350 nm (TB and FB) excitation/emission wavelengths, respectively. Quantitation limits provided by the supramolecular solvent-based microextraction (SUSME)/LC/fluorescence detection proposed method for the determination of CB, TB and FB in fruits and vegetables were 14.0, 1.3 and 0.03 microg kg(-1), respectively, values far below the current maximum residue levels (MRLs) established by the European Union, i.e. 100-2000 microg kg(-1) for CB, 50-5000 microg kg(-1) for TB and 50 microg kg(-1) for FB. The precision of the method, expressed as relative standard deviation, for inter-day measurements (n=13) was 3.3% for CB (50 microg kg(-1)), 3.5% for TB (10 microg kg(-1)) and 2.8% for FB (0.5 microg kg(-1)) and recoveries for fruits (oranges, tangerines, lemons, limes, grapefruits, apples, pears and bananas) and vegetables (potatoes and lettuces) fortified at the microg kg(-1) level were in the interval 93-102%.

A supramolecular solvent made up of vesicles of decanoic acid in the nano- and microscale regimes dispersed in a continuous aqueous phase is proposed for the extraction/preconcentration of benzimidazolic fungicides (BFs) from river and underground water samples prior to their determination by liquid chromatography (LC)/fluorimetry. The solvent is produced from the coacervation of decanoic acid aqueous vesicles by the action of tetrabutylammonium (Bu(4)N(+)). Carbendazim (CB), thiabendazole (TB) and fuberidazole (FB) are extracted on the basis of hydrophobic and pi-cation interactions and the formation of hydrogen bonds. The extraction provides high preconcentration factors (160 for CB and 190 for TB and FB), requires a short time (the procedure takes less than 20 min and several samples can be simultaneously processed) and a low sample volume (20 mL), and avoids the use of toxic organic solvents. Because of the absence of matrix interferences and the low viscosity of the extracts, these can be directly injected into the chromatographic system without the need of cleaning-up or diluting them. Recoveries are not influenced by the presence of salt concentrations up to 1 M. The proposed method provides detection limits for the determination of CB, TB and FB in natural waters of 32, 4 and 0.1 ng L(-1), respectively, and a precision, expressed as relative standard deviation (n=11) of 5.5% for CB (100 ng L(-1)), 4.0% for TB (80 ng L(-1)) and 2.5% for FB (30 ng L(-1)). Recoveries obtained by applying this approach to the analysis of river and underground water samples fortified at the ng L(-1) level are in the intervals 75-83, 95-102 and 97-101% for CB, TB and FB, respectively.