Solvent extraction and extraction–voltammetric determination of phenols using room temperature ionic liquid

The phenolic compounds phenol, 4-nitrophenol, 2,4-dinitrophenol, 2,6-dinitrophenol, 1-naphthol, 2-naphthol, and 4-chlorophenol are extracted nearly quantitatively from aqueous solution into the room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMImPF₆) in molecular form at pH<pK_a. Picric acid is extracted efficiently in anionic form. Recovery of pyrocatechol and resorcinol is much lower. The effect of pH, phenol concentration, and volume ratio of aqueous and organic phases were studied. Ionic liquid BMImPF₆ is shown to be suitable for extraction–voltammetric determination of phenols without back-extraction or addition of support electrolyte. The electrochemical window of BMImPF₆ at various electrodes was determined, and voltammetric oxidation of phenols and reduction of nitrophenols in BMImPF₆ was studied.     

Identification and extraction—spectrophotometric or extraction—fluorimetric determination of organic nitrogen-containing triiodides, new biologically active compounds

A method for the identification of organic triiodides is proposed, and rapid, highly sensitive procedures for the extraction-spectrophotometric and extraction-fluorometric determination of medicinal preparations as ion associates with hydroxyxanthene (Eosin) and triphenylmethane (Bromothymol Blue) dyes. The formation of 1 : 1 ion associates with an absorption maximum at 545 nm (430 nm for ion associates with Bromothymol Blue) and a fluorescence maximum at 560 nm was detected. The ion associates were extracted with chloroform from a water-ethanol solution at pH 6.86 and 9.18. The detection limits were c_min ≈ 4.3 × 10^-7 M for the extraction-spectrophotometric and c_min ≈ 8.6 sx 10^-8 M for the extraction-fluorimetric procedure; RSD ≤2%. The developed procedures can be used for controlling medicinal preparations and monitoring biological materials     

Interfacial behavior of plant proteins — novel sources and extraction methods

Understanding the air-water and oil-water interfacial behavior of plant proteins is crucial for developing stable emulsions and foams in food systems. Plant crops are often processed into protein extracts with high purity, which primarily consist of globulins. These globulins are often unable to form stiff interfacial layers owing to their compact and highly aggregated state and have inferior functionality compared with animal-derived proteins from milk or eggs. Much of the current focus is on modifying these proteins, whereas better interface stabilizing functionality can also be obtained by choosing more targeted protein extraction methods. This review will highlight the benefits and drawbacks of current and novel protein sources and protein extraction methods with respect to interfacial properties.     

The determination of pharmaceutical residues in cooked and uncooked marine bivalves using pressurised liquid extraction, solid-phase extraction and liquid chromatography–tandem mass spectrometry

An optimised and validated method for the determination of pharmaceutical residues in blue mussels (Mytilus spp.) is presented herein, as well as an investigation of the effect of cooking (by steaming) on any potential difference in human exposure risk. Selected pharmaceuticals included two non-steroidal anti-inflammatory drugs (diclofenac and mefenamic acid), an antibiotic (trimethoprim), an anti-epileptic (carbamazepine) and a lipid regulator (gemfibrozil). An in vivo exposure experiment was set up in the laboratory in which mussels were exposed either directly by injection (10 ng) or daily through spiked artificial seawater (ASW) over 96 h. In liquid matrices, pharmaceutical residues were either determined using liquid chromatography–tandem mass spectrometry (LC-MS/MS) directly, or in combination with solid-phase extraction (SPE) for analyte concentration purposes. The extraction of pharmaceuticals from mussel tissues used an additional pressurised liquid extraction step prior to SPE and LC-MS/MS. Limits of quantification of between 2 and 46 ng L^?1 were achieved for extracted cooking water and ASW, between 2 and 64 μg L^?1 for ASW in exposure tanks, and between 4 and 29 ng g^?1 for mussel tissue. Method linearities were achieved for pharmaceuticals in each matrix with correlation coefficients of R ²?>?0.975. A selection of exposed mussels was also cooked (via steaming) and analysed using the optimised method to observe any effect on detectable concentrations of parent pharmaceuticals present. An overall increase in pharmaceutical residues in the contaminated mussel tissue and cooking water was observed after cooking.

Enhanced methods for conditioning, storage, and extraction of liquid and solid samples of manure for determination of steroid hormones by solid-phase extraction and gas chromatography–mass spectrometry

Hormones are among the highest-impact endocrine disrupters affecting living organisms in aquatic environments. These molecules have been measured in both wastewater and sewage sludge. Analytical techniques for such matrices are well described in the literature. In contrast, there is little information about the analysis of hormones in animal waste. The objectives of this study were, first, to propose a method for conditioning swine manure samples (addition of formaldehyde, separation of the solid and liquid phases, and duration of storage) in order to determine hormones in the liquid fraction of manure by solid-phase extraction (SPE) coupled with gas chromatography–mass spectrometry (GC–MS). Our results showed that analysis of hormones was affected by matrix changes which occurred during freezing and thawing and after addition of formaldehyde, an additive frequently used to preserve environmental samples. Thus, our results argue for the conditioning of samples without formaldehyde and for separating the solid and liquid fractions of manure before freezing. Second, this study reports on the use of a liquid extraction method coupled with SPE and GC–MS analysis for determination of hormones in the solid fraction of manure. Under the conditions selected, hormone recoveries were between 80 and 100%. Finally, the optimized method was used to quantify hormones in both liquid and solid fractions of swine manure from different breeding units. High levels of estrone and α-estradiol were found in samples whereas β-estradiol was detected in smaller amounts. Estriol and progesterone were mainly found in manure from the gestating sow building whereas testosterone was detected in manure from male breeding buildings.     

Multidimensional gas chromatography–mass spectrometry determination of 3-alkyl-2-methoxypyrazines in wine and must. A comparison of solid-phase extraction and headspace solid-phase extraction methods

Two different strategies for the quantitative determination of 3-alkyl-2-methoxypyrazines in wine and must have been developed and validated. Comparison between both the techniques has been presented and the most adequate has been applied to the determination of these compounds in different samples of wine, made from several varieties of grapes, and also in different samples of must made from Cabernet Sauvignon grapes. Both the methods consisted of a dynamic headspace coupled with a solid-phase extraction (HS–SPE) and solid-phase extraction (SPE) directly from the sample, coupled with multidimensional gas chromatography–mass spectrometry system (MDGC–MS). Both of them require resins LiChrolut EN, and analyte elution has been carried out with dichloromethane. The repeatability of both methodologies was evaluated at two concentration levels. The relative standard deviations (RSD%) were acceptable in every case, but smaller when working with HS–SPE. The recoveries obtained for the three analytes with the two methodologies were almost 100%, with the exception of IBMP, which had a recovery of only 70% with HS–SPE. The linearity was satisfactory with both methods for the range of occurrence of methoxypyrazines in wine and must. The limits of detection of the direct SPE technique were much lower than those of HS–SPE in every case. Direct SPE method detection limits ranged from 0.09 to 0.15 ng L⁻¹. The method based on direct SPE was chosen finally because it had better detection limits and was easier and quicker than the HS–SPE-based method. It has been applied to the determination of these components in 36 wine and 17 musts samples. The quantitative results suggest that the Spanish wines show meaningless amounts of these compounds. IBMP has been found just in between 1.9 and 15 ng L⁻¹.     

Fabrication of titania and titania–silica aerogels using rapid supercritical extraction

Titania (TiO₂) and titania–silica (TiSi) aerogels are suitable for photocatalytic oxidation of volatile organic compounds for pollution mitigation; however, methods for fabricating these aerogels can be complex. In this work we describe the use of a rapid supercritical extraction (RSCE) technique to prepare TiO₂ and TiSi aerogels in as little as 8 h. The RSCE technique uses a metal mold and a four-step hydraulic hot press procedure to bring the solvents in the sol–gel pores to a supercritical state and control the supercritical fluid release process. Resulting TiO₂ aerogels were powdery with BET surface areas of 130–180 m²/g, pore volumes ~0.5 cm³/g and skeletal densities of 3.6 g/mL. Monolithic TiSi aerogels were made using two different methods. An impregnation process, in which titania precursor was added to a silica sol–gel, took 4–8 days to complete with a 7-h RSCE and resulted in translucent aerogels with high surface area (560–650 m²/g) and pore volume (2.0–2.6 cm³/g), bulk densities ranging from 0.1 to 0.4 g/mL and skeletal densities of 2.3 g/mL. A co-precursor method for preparing TiSi aerogels took 8 h to complete. The precursor chemical mixture was poured directly into the mold and processed in a 7-h RSCE process. The resulting aerogels were opaque, with high surface areas (510–580 m²/g), low bulk density (0.03 g/mL), skeletal densities of 2 g/mL and pore volumes of 2.6–3.5 cm³/g. Preliminary solar simulator studies show that TiO₂ and TiSi aerogels are capable of photocatalytic degradation of methylene blue in aqueous solution.     

Analysis of dinitro- and amino-nitro-toluenesulfonic acids in groundwater by solid-phase extraction and liquid chromatography–mass spectrometry

A reversed-phase LC–MS method with quadrupole-time of flight (QTOF) detection has been developed for the determination of four dinitro-toluenesulfonic acids and two amino-nitro-toluenesulfonic acids in groundwater. The analytes were separated by HPLC with 0.1% (v/v) formic acid as mobile phase modifier compatible with mass spectrometric detection. QTOF-MS analysis with negative ion electrospray ionization afforded good selectivity and sensitivity for analysis of the dinitro- and amino-nitro-toluenesulfonic acids. Structure elucidation and confirmation were accomplished by tandem mass spectrometry. Characteristic ions resulting from the loss of NO, NO₂, and SO₂ from the [M–H]^– ions were detected. An intense fragment ion at m/z 80 representing the [SO₃]^– ion was detected for all dinitro- and amino-nitro-toluenesulfonic acids. Solid-phase extraction using a co-polymer cartridge was developed for preconcentration of the analytes from water. Good recovery (>85%) was achieved when 0.1% formic acid was added into the water samples before extraction. Method detection limits ranged from 10 to 76 ng L^–1 for the targeted compounds when 10 mL water was analyzed. Groundwater samples collected from wells close to a former ammunition plant in Stadtallendorf, Germany, were analyzed for the dinitro- and amino-nitro-toluenesulfonic acids.     

Electromembrane extraction (EME)—an easy, novel and rapid extraction procedure for the HPLC determination of fluoroquinolones in wastewater samples

For the first time, an electromembrane extraction combined with a HPLC procedure using diode array and fluorescence detection has been developed for the determination of seven widely used fluoroquinolones (FQs): marbofloxacin, norfloxacin, ciprofloxacin, danofloxacin, enrofloxacin, gatifloxacin and grepafloxacin. The drugs were extracted from acid aqueous sample solutions (pH 5), through a supported liquid membrane consisting of 1-octanol impregnated in the walls of a S6/2 Accurel® polypropylene hollow fiber, to an acid (pH 2) aqueous acceptor solution inside the lumen of the hollow fiber. The main operational parameters were optimized, and extractions were carried out in 15 min using a potential of 50 V. Enrichment factors of 40–85 have been obtained using only 15 min of extraction time versus 330 min used in a previously proposed hollow-fiber liquid-phase microextraction procedure. The procedure allows low detection and quantitation limits of 0.005–0.07 and 0.007–0.15 μg?L^?1, respectively. The proposed method was successfully applied to the FQs analysis in urban wastewaters.

Simultaneous spectrophotometric determination of Tungsten and Molybdenum with Thiocyanate after α-Benzoinoxime extraction

The extractability of tungsten α-benzoinoximate by chloroform as a function of the reagent concentration and acidity has been studied. In 0.5 M hydrochloric acid solution the extraction coefficient for tungsten (~ l p.p.m.) is given by the relation

An acidity range of 0.01–1 M provides favorable extraction coefficients. Tungsten can be separated by α-benzoinoxime extraction from much iron and most other metals. Molybdenum accompanies tungsten quantitatively and the two elements can be determined simultaneously by the familiar thiocyanate method if the absorbance of the isopropyl ether extract is measured at 405 mμ and 490 (or 475) mμ. As little as 1 μg W can thus be determined in the presence of 10 μg Mo without separation.     

Environmentally friendly analysis of emerging contaminants by pressurized hot water extraction–stir bar sorptive extraction–derivatization and gas chromatography–mass spectrometry

This work describes the development, optimization, and validation of a new method for the simultaneous determination of a wide range of pharmaceuticals (beta-blockers, lipid regulators…) and personal care products (fragrances, UV filters, phthalates…) in both aqueous and solid environmental matrices. Target compounds were extracted from sediments using pressurized hot water extraction followed by stir bar sorptive extraction. The first stage was performed at 1,500 psi during three static extraction cycles of 5 min each after optimizing the extraction temperature (50–150 °C) and addition of organic modifiers (% methanol) to water, the extraction solvent. Next, aqueous extracts and water samples were processed using polydimethylsiloxane bars. Several parameters were optimized for this technique, including extraction and desorption time, ionic strength, presence of organic modifiers, and pH. Finally, analytes were extracted from the bars by ultrasonic irradiation using a reduced amount of solvent (0.2 mL) prior to derivatization and gas chromatography–mass spectrometry analysis. The optimized protocol uses minimal amounts of organic solvents (<10 mL/sample) and time (≈8 h/sample) compared to previous existing methodologies. Low standard deviation (usually below 10 %) and limits of detection (sub-ppb) vouch for the applicability of the methodology for the analysis of target compounds at trace levels. Once developed, the method was applied to determine concentrations of these compounds in several types of sample (wastewater, seawater, pore water, and sediment) from Cadiz Bay (SW Spain). To our knowledge, these findings represent the first information available on the presence of some of the target compounds in the marine environment.     

Development of molecularly imprinted-solid phase extraction combined with dispersive liquid–liquid microextraction for selective extraction and preconcentration of triazine herbicides from aqueous samples

In this study, a sensitive and developed method based on the use of molecularly imprinted-solid phase extraction along with dispersive liquid–liquid microextraction has been reported for selective extraction and pre-concentration of triazine pesticides from aqueous samples. Molecularly imprinted microspheres (template, atrazine) were synthesized using precipitation polymerization and used as sorbent in SPE procedure. A model solution containing the studied pesticides was slowly passed through the atrazine-MIP cartridge. The adsorbed analytes were eluted with methanol, mixed with carbon tetrachloride (as extraction solvent) and rapidly injected into deionized water. In this process, the analytes were extracted into fine droplets of carbon tetrachloride and the fine droplets were sedimented in bottom of the conical test tube by centrifugation. Finally, GC-FID was used for the separation and determination of analytes in the sedimented phase. Some important parameters affecting the performance of developed method were completely investigated. The linear ranges of calibration curves were wide and limits of detection and limits of quantification were between 0.2–7 and 0.5–20 ng mL^?1, respectively. The relative standard deviation obtained for six repeated experiments of atrazine (10 ng mL^?1) was 3.1 %. The relative recoveries obtained for the atrazine in the spiked samples were within in the range of 92–98 %.     

Parameters of cation “hardness” and “softness” and application thereof for calculation of extraction constants

Analysis of published data was performed on the basis of solvation energies of a number of “transition” and “soft” cations. A dependence of the solvation energy of cations on the donor and acceptor numbers of the solvent was derived. Donor and acceptor ability parameters of Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, Cd²⁺, and Tl⁺ were calculated. The resultant parameters were used to calculate the extraction constants of the specified cations with di-2-ethylhexyl-phosphoric acid (DEHPA) solution in neutral solvents; the model represented has a good predictive power.     

Determination of α-chaconine and α-solanine in commercial potato crisps by QuEChERS extraction and UPLC-MS/MS

A simple and fast analytical method for the determination of the main steroidal glycoalkaloids, α-chaconine and α-solanine, in commercial potato crisps, based on QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) extraction and ultra performance liquid chromatography coupled with an electrospray ionization triple-quadrupole tandem mass spectrometer (UPLC-MS/MS) in the multiple reaction monitoring mode was established and validated. The sample preparation procedure involves the extraction of the analytes with acidified acetonitrile and simultaneous liquid-liquid partitioning achieved by an addition of anhydrous magnesium sulfate and sodium acetate without any further clean-up steps. The limits of quantification (LOQs) for α-chaconine and α-solanine were 31 μg kg^?1 and 16 μg kg^?1 of fresh mass, respectively, at the signal-to-noise ratio (S/Ns) of 10. The method was applied in a survey of the content of α-chaconine and α-solanine in twenty commercial potato crisps from different brands. The results showed that all the products contained α-chaconine and α-solanine in widely varying concentrations. The amount of α-chaconine was higher than that of α-solanine in all samples.     

Selective liquid-liquid extraction of xylene isomers and ethylbenzene through inclusion by branchedα-cyclodextrins

Branched-cyclodextrins (CDs) such as glucosyl--CD(G--CD) were found to be very effective reagents for selective liquid-liquid extraction of xylene isomers and ethylbenzene since their inclusion complexes did not precipitate and handling of solids was not necessary. Reaction temperatures higher than room temperature did not increase the yield. The inclusion complexation proceeded fast. The liquid-liquid extraction process was found to be energy-saving and not time-consuming.     

Static–dynamic sequential superheated liquid extraction of phenols and fatty acids from alperujo

Superheated liquids of different polarity have been used for sequential extraction of fatty acids and phenols from alperujo. Multivariate methodology has been used to optimise the static–dynamic extraction. Forty-two minutes are required to complete extraction (20 mg/kg of fatty acids and up to 2,200 mg/kg of hydroxytyrosol in the raw material used). The efficacy of the extraction has been demonstrated and compared with that of conventional methods (Folch and stirring-based methods for fatty acids and phenols, respectively), which needed 4.5 and 24 h for the extraction of fatty acids and phenols, respectively. The non-polar and polar extracts were injected into GC–MS and HPLC–MS–MS equipment, respectively, for individual separation–quantification of the target compounds. The simplicity of the experimental setup and the low costs of the raw material make the proposed method advisable when extraction of both fractions is required.     

2,2′-Dipyridyl and 1,10-phenanthroline in the synergetic extraction of Eu3+

The thermodynamics of the extraction of Eu³⁺ by thenoyltrifluoroacetone (HTTA) and by mixtures of HTTA and bidentate amine bases such as 2,2-dipyridyl (Dipy) and 1,10-phenanthroline (Phen) in benzene from an aqueous phase fixed to 0.1M ionic strength (NaClO₄), pH 3.9, has been investigated. Phenanthroline forms both the Eu(TTA)₃·Phen and Eu(TTA)₃·2Phen species, which are much stronger than the dipyridyl complexes. The diluent effect on the extraction is also studied.     

Determination of ochratoxin A in pig tissues by liquid–liquid extraction and clean-up and high-performance liquid chromatography

A fast, simple, and sensitive HPLC–FD method is described for determination of ochratoxin A (OTA) in pig kidney and muscle; a small mass (<2.5 g) of sample and a relatively small volume (<15 mL) of a non-halogenated extraction solvent are required. Ochratoxin B, systematically absent from all the samples investigated, was used as internal standard. Liquid–liquid partition was used for sample clean-up. Recoveries at the 1 ng g^–1 level were 86±15% and 74±8% for kidney and muscle, respectively, and detection limits were 0.14 and 0.15 ng g^–1. Clean-up by solid-phase extraction (SPE) is required for pig liver. A survey of the OTA content of tissues of pigs slaughtered in southern Italy revealed that 52 out of 54 analysed samples were contaminated; the OTA concentration in kidney ranged between 0.26 and 3.05 ng g^–1. The effect of measurement precision on compliance with legal limits is also discussed.     

LC–UV determination of atrazine and its principal conversion products in soil after combined microwave-assisted and solid-phase extraction

A multiresidue method developed for the analysis of atrazine and its principal conversion products, deisopropylatrazine (DIA), deethylatrazine (DEA) and hydroxyatrazine (HA), in soil is presented. The method is based on the microwave-assisted extraction (MAE) of soil with aqueous methanol followed by solid-phase extraction (SPE) of the extracts and subsequent analysis by LC–UV with a diode array detector. MAE operational parameters (extraction solvent, extractant volume) were optimized with respect to extraction efficiency of the target compounds from soils with 2.5% organic matter (OM) content. Recoveries above 80% were obtained for all solutes. Soil OM content did not affect analyte recoveries. Recoveries from fresh and aged residues, the latter weathered under cold storage conditions, were not statistically different. Finally, MAE was found to be superior in terms of extraction efficiency, sample throughput, and solvent consumption to conventional flask-shaking extraction.     

Determination of tetrabromobisphenol-A,tetrachlorobisphenol-A and bisphenol-A in soil by ultrasonic assisted extraction and gas chromatography–mass spectrometry

In this work, an isotope dilution method for the determination, in agricultural and industrial soil samples, of tetrabromobisphenol-A, tetrachlorobisphenol-A and bisphenol-A by gas chromatography–mass spectrometry was developed. The compounds were extracted from soil by sonication assisted extraction in small columns (SAESC) with a low volume of ethyl acetate as extraction solvent. For dirty soil samples, such as industrial soils, a simultaneous clean-up on an acidified Florisil–anhydrous sodium sulfate mixture was carried out to remove interferences. After extraction, solvent was evaporated and analytes were derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and determined by isotope dilution gas chromatography with electron impact mass spectrometric detection in the selected ion monitoring mode (GC–MS–SIM), using ¹³C₁₂ labeled compounds as internal standards. Recoveries from spiked samples were between 88% and 108% and the estimated limits of detection (S/N = 3) varied from 30 pg g⁻¹ to 90 pg g⁻¹. The response obtained with this method was linear over the range assayed, 5–300 ng ml⁻¹, with correlation coefficients equal or higher than 0.999. The validated method was used to investigate the levels of these phenolic compounds in soil samples collected from different locations in Spain. Bisphenol-A was detected in all samples at concentrations from 0.7 ng g⁻¹ to 4.6 ng g⁻¹ in agricultural soils and from 1.1 ng g⁻¹ to 44.5 ng g⁻¹ in industrial soils. Tetrabromobisphenol-A was found in various soil samples at levels in the range of 3.4–32.2 ng g⁻¹ in industrial soils and at 0.3 ng g⁻¹ in one agricultural soil, whereas tetrachlorobisphenol-A was not detected.