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The importance of lipidomics to unveil crucial aspects in the nutrition field is afforded in this article. With this aim, historical facts such as demonization of fats, enthronization of carbohydrates, and subsequent changes in the food pyramid are first discussed. After considering basic and analytical aspects of lipidomics and the upstream information this omics provides, its key role in personalized nutrition (PN), and the importance of lipids as nutrition biomarkers are critically discussed by appropriate examples. Pendent challenges to clarify the role of lipidomics in nutrition are overcome limiting factors, design of new lipidomics-based biomarkers, unveil mechanisms involved in lipidomics processes, and integrate lipidomics with other omics for a more complete and validated information useful in PN. The conclusions of this study also include the scant role of analytical chemists in the lipidomics-nutrition binomial, basically supported on analytical data., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Sweat is gaining popularity in clinical metabolomics as this biofluid is non-invasively sampled and its composition is modified by several pathologies. There is a lack of standardized strategies for collection of human sweat. Most studies have been carried out with fresh sweat collected after stimulation. A promising and simple alternative is sampling dry sweat by a solid support impregnated with a suited solvent. This research was aimed at comparing the metabolomics coverage provided by dry sweat collected by two solid supports (gauzes and filter papers) impregnated with different solvents. The dissolved dry sweat was analyzed by a dual approach: gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Among the tested sampling strategies, filter paper impregnated with 1:1 (v/v) ethanol‒phosphate buffer resulted the combination providing the highest metabolomics coverage (tentative identification of one hundred seventy-five compounds). Dry and fresh sweat were compared by using pools from the same individuals to evaluate compositional differences. Families of metabolites such as carnitines, sphingolipids and N-acyl-amino acids, among others, were exclusively identified in dry sweat. Comparison of both samples allowed concluding that dry sweat is better for analysis of low polar metabolites and fresh sweat is more suited for polar compounds. As most of the identified metabolites are involved in key biochemical pathways, this study opens interesting possibilities to the use of dry sweat as a source of metabolite markers for specific disorders. Sampling of dry sweat could provide a standardized approach for collection of this biofluid, thus overcoming the variability limitations of fresh sweat., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Professionals belonging to very different areas of expertise are usually involved in research on the cultural heritage. Among the names given to the person in charge of analyses are conservator or material scientist, as the most usual, but never "analytical chemist", despite analytical equipment, obtainment of analytical data and application of chemometrics approaches to obtain analytical results are always involved in their tasks. This article tries to be a call of attention to analytical chemists by showing the different areas within the research on cultural heritage in which they should be involved to provide the necessary analytical information. Examples of the analytical equipment involved in these studies, the research on pigments, dyes, binders and coatings, dating and cleaning of artworks are given, thus showing that analytical information on chemical aspects related to research on the cultural heritage should be, evidently, conducted in cooperation with analytical chemists., (Copyright © 2019. Published by Elsevier B.V.)

A disposable and miniaturised optical sensor based on colorimetric solid-phase extraction has been designed using poly(styrene-divinylbenzene) membrane disks modified with the colorimetric reagent pyridoxal salicyloylhydrazone to determine the aluminium concentration in aqueous solutions. The extraction of Al(III) ions by the reagent immobilised onto a disk allows the quantification directly on the adsorbent surface by a miniature portable reflectance spectrometer with an optical fibre at 434 nm. The optimisation of the sensing system was carried out by a fractional factorial design 3 3-1 considering the extraction pH, amount of ligand immobilised onto the disk and time of immobilisation as experimental factors. The linear dynamic range of the sensor response ranged from 0.18 to 2 mg L -1  Al(III) with a detection limit of 0.18 mg L -1 (n = 10), being the precision of 6.3% for 1 mg L -1  Al(III) (n = 10, confidence level of 95%). The proposed method was successfully applied to the analysis of aluminium in leachates from cookware, antacids and hygienic care products, as contribution to the concern about aluminium as a known systemic toxicant at high doses., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Vitamin D has been widely determined in clinical trials to elucidate its biochemical involvement in a great number of pathologies. The analysis of vitamin D and its hydroxymetabolites in biofluids such as serum or plasma is a challenging task due to limitations associated to the low concentrations of some metabolites (typically, dihydroxymetabolites), methodological interferences, and the low stability of the compounds. Among these limitations, efforts have been targeted at optimizing instrumental improvements to develop more sensitive and selective methods, while the stability of vitamin D and metabolites has not been exhaustively evaluated. In this research, several aspects regarding the short-term storage conditions of human serum have been studied to evaluate their influence on the determination of vitamin D 3 and metabolites. An experimental plan has been applied to assess the influence of two relevant parameters: the storage temperature for a period of two months and the number of freeze-thaw cycles. The storage temperature affected in a different manner to vitamin D 3 and its metabolites, being vitamin D 3 and 1,25-dihydroxyvitamin D 3 the two analytes more affected by this parameter. Concerning the freeze-thaw cycles, this variable must be limited to two cycles owing to its significant influence on the variability for quantitation of dihydroxymetabolites in human serum. Finally, lyophilization was also tested to check if serum concentrations of vitamin D 3 and its metabolites were affected by this preprocessing step. The results revealed that only vitamin D 3 experienced a decrease in serum concentration after two months, which does not constitute a real problem as vitamin D 3 is not currently a crucial parameter to be determined in clinical trials due to its scant biological activity., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The recent growing interest in primary fatty acid amides (PFAMs) is due to the broad range of physiological effects they exhibit as bioindicator of pathological states. These bioactive lipids are usually in biological samples at the nanomolar level, making their detection and identification a challenging task. A method for quantitative analysis of seven main PFAMs (lauramide, myristamide, linoleamide, palmitamide, oleamide, stearamide and behenamide) in four human biofluids -namely, urine, plasma, saliva and sweat- is here reported. Two sample preparation procedures were compared to test their efficiency in each biofluid: solid-phase extraction (SPE) and protein precipitation. The latter was the best for plasma and urine, while the analysis of saliva and sweat required an SPE step for subsequent suited determination of PFAMs. Detection of the seven metabolites was performed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) in multiple reaction monitoring (MRM) mode. Quantitative analysis was supported on the use of stable isotopically labeled internal standards (SIL-ISs) in the calibration method, which required the synthesis of each IS from the precursor deuterated fatty acids. Detection limits for the target analytes were within 0.3-3 ng mL -1 . The method was applied to a small cohort of male and female volunteers (n = 6) to estimate the relative concentration profiles in the different biofluids. The analytical features of the method supported its applicability in clinical studies aimed at elucidating the role of PFAMs metabolism., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A tandem system based on the coupling of a bulk liquid membrane and a flow injection analysis for the separation, preconcentration and spectrophotometric determination of copper in saline water is presented. The ligand pyridine-2-acetaldehyde benzoylhydrazone has been used as a carrier in the liquid membrane as well as a spectrophotometric reagent for UV-VIS detection. Simultaneous and sequential experimental designs were used to optimise the chosen variables of each technique, respectively. The metal was separated and preconcentrated from the sample with an efficiency of 100.5 ± 0.9% and a metal preconcentration factor of 16.1. The on-line FIA determination was accomplished after metal complexation by the reagent at pH 3. A linear response was obtained in a range from 6.9 to 984.5 µg L -1 Cu(II), providing a detection limit of 1.8 µg L -1 . Saline matrix and other metal ions were not cause of interferences with relative errors below 4.6% for 50 µg L -1 of Cu(II) determination. The proposed tandem system was successfully tested using a TMDA-62 certified reference material providing a relative error of + 1.9%; it was also applied to the Cu(II) determination in coastal seawater samples with low relative errors ranging from - 3.8% to 0.0% (using DPASV as reference method)., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Endocannabinoids are lipids with a key role in physiological processes such as the immune response or the metabolism. This involvement explains their association to pathologies such as cancer, obesity or multiple sclerosis. The determination of endocannabinoids constitutes a challenge for clinical laboratories due to the variety of biological matrices and the wide range of concentrations at which they can be found. This research deals with the comparison of three sample preparation strategies (viz., on-line SPE, off-line SPE for interferents removal, and protein precipitation) for subsequent LC-MS/MS analysis of 14 endocannabinoids and analogous compounds in serum. As a result, the on-line coupling between SPE and LC-MS/MS is proposed as the best approach for this determination. The proposed method allows full automation of the overall process, shortening of the analysis time, and avoidance of errors associated with sample preparation steps. The improvement in sensitivity and selectivity thus achieved allows obtaining quantification limits at the pg mL -1 level, which makes possible the application of the method for clinical studies., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Sweat is a promising biofluid scarcely used in clinical analysis despite its non-invasive sampling. A more frequent clinical use of sweat requires to know its whole composition, especially concerning to non-polar compounds, and the development of analytical strategies for its characterization. The aim of the present study was to compare different sample preparation strategies to maximize the detection of metabolites in sweat from humans collected after practicing moderate exercise. Special emphasis was put on non-polar compounds as they have received scant attention in previous studies dealing with this biofluid. Sample preparation by liquid-liquid extraction (LLE) using extractants with different polarity index was compared to deproteination. Then, derivatization by methoxymation with subsequent silylation was compared to direct analysis of sweat extracts to check the influence of derivatization on the subsequent determination of volatile organic compounds (VOCs). 135 compounds were tentatively identified by combining spectral and retention time information after analysis by gas chromatography coupled to mass spectrometry in high resolution mode (GC-TOF/MS). Lipids, VOCs, benzenoids and other interesting metabolites such as alkaloids and ethanolamines were identified. Among the tested protocols, methyoxiamination plus silylation after LLE with dichloromethane was the best option to obtain a representative snapshot of sweat metabolome collected from different body parts after moderate exercise. Passive and active sweat pools from a cohort of volunteers (n = 6) were compared to detect compositional differences which can be explained by the sampling process and sweating induction. As most of the identified compounds are metabolites involved in key biochemical pathways, this study opens new opportunities to extend the applicability of human sweat as a source of metabolite biomarkers of pathologies or specific processes such as dehydration or nutritional unbalance., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The present article has as main aim to show analytical chemists interested in forensic analysis the world they will face if decision in favor of being a forensic analytical chemist is adopted. With this purpose, the most outstanding aspects of forensic analysis in dealing with sampling (involving both bodily and no bodily samples), sample preparation, and analytical equipment used in detection, identification and quantitation of key sample components are critically discussed. The role of the great omics in forensic analysis, and the growing role of the youngest of the great omics -metabolomics- are also discussed. The foreseeable role of integrative omics is also outlined., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Stevia is a currently well-known plant thanks to the presence of steviol glycosides, which are considered as sweeteners obtained from a natural source. In this research, a method based on LC-MS/MS by using a triple quadrupole detector was developed for quantitation of 8 steviol glycosides in extracts from Stevia leaves. The ionization and fragmentation parameters for selected reaction monitoring were optimized. Detection and quantitation limits ranging from 0.1 to 0.5ng/mL and from 0.5 to 1ng/mL, respectively, were achieved: the lowest attained so far. The steviol glycosides were quantified in extracts from leaves of seven varieties of Stevia cultivated in laboratory, greenhouse and field. Plants cultivated in field presented higher concentration of steviol glycosides than those cultivated in greenhouse. Thus, the way of cultivation clearly influences the concentration of these compounds. The inclusion of branches together with leaves as raw material was also evaluated, showing that this inclusion modifies, either positively or negatively, the concentration of steviol glycosides., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Major threats in metabolomics clinical research are biases in sampling and preparation of biological samples. Bias in sample collection is a frequently forgotten aspect responsible for uncontrolled errors in metabolomics analysis. There is a great diversity of blood collection tubes for sampling serum or plasma, which are widely used in metabolomics analysis. Most of the existing studies dealing with the influence of blood collection on metabolomics analysis have been restricted to comparison between plasma and serum. However, polymeric gel tubes, which are frequently proposed to accelerate the separation of serum and plasma, have not been studied. In the present research, samples of serum or plasma collected in polymeric gel tubes were compared with those taken in conventional tubes from a metabolomics perspective using an untargeted GC-TOF/MS approach. The main differences between serum and plasma collected in conventional tubes affected to critical pathways such as the citric acid cycle, metabolism of amino acids, fructose and mannose metabolism and that of glycerolipids, and pentose and glucuronate interconversion. On the other hand, the polymeric gel only promoted differences at the metabolite level in serum since no critical differences were observed between plasma collected with EDTA tubes and polymeric gel tubes. Thus, the main changes were attributable to serum collected in gel and affected to the metabolism of amino acids such as alanine, proline and threonine, the glycerolipids metabolism, and two primary metabolites such as aconitic acid and lactic acid. Therefore, these metabolite changes should be taken into account in planning an experimental protocol for metabolomics analysis., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The determination of physiological levels of amino acids is important to aid in the diagnosis and treatment of several diseases and nutritional status of individuals. Amino acids are frequently determined in biofluids such as blood (serum or plasma) and urine; however, there are less common biofluids with different concentration profiles of amino acids that could be of interest. One of these biofluids is sweat that can be obtained in a non-invasive manner and is characterized by low complex composition. The analysis of amino acids in human sweat requires the development of sample preparation strategies according to the sample matrix and small collected volume. The influence of sample preparation on the quantitative analysis of amino acids in sweat by LC-MS/MS has been assessed through a comparison between two strategies: dilution of sweat and centrifugal microsolid-phase extraction (c-μSPE). In both cases, several dilution factors were assayed for in-depth knowledge of the matrix effects, and the use of c-μSPE provided the best results in terms of accuracy. The behavior of the target analytes was a function of the dilution factor, thus providing a pattern for sample preparation that depended on the amino acid to be determined. The concentration of amino acids in sweat ranges between 6.20 ng mL(-1) (for homocysteine) and 259.77 µg mL(-1) (for serine) with precision, expressed as relative standard deviation, within 1.1-21.4%., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Metabolomic analysis of exhaled breath condensate (EBC) requires an unavoidable sample preparation step because of the low concentration of its components, and potential cleanup for possible interferents. Sample preparation based on protein precipitation (PP), solid-phase extraction (SPE) by hydrophilic and lipophilic sorbents or lyophilization has demonstrated that the analytical sample from the last is largely the best because lyophilization allows reconstitution in a volume as small as required (preconcentration factors up to 80-times with respect to the original sample), thus doubling the number of detected compounds as compared with the other alternatives (47 versus 25). In addition, PP and/or SPE cleanup are unnecessary as no effect from the EBC components removed by these steps appears in the chromatograms. The total 49 EBC compounds tentatively identified and confirmed by MS/MS in this research include amino acids, fatty acids, fatty amides, fatty aldehydes, sphingoid bases, oxoanionic compounds, imidazoles, hydroxy acids and aliphatic acyclic acids., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The influence of the inclusion of a stable isotopic labeled internal standard (SIL-IS) on the quantitative analysis of hydroxyeicosatetranoic acids (HETEs) in human serum is evaluated in this research. A solid-phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) platform, one of the preferred approaches for targeted analysis of biofluids through the selected reaction monitoring (SRM) operational mode, was used to determine HETEs. These compounds were chosen as targeted metabolites because of their involvement in cardiovascular disease, cancer and osteoporosis. 15HETE-d8 was chosen as internal standard to evaluate matrix effects. Thus, the physico-chemical properties of the SIL-IS were the basis to evaluate the analytical features of the method for each metabolite through four calibration models. Two of the models were built with standard solutions at different concentration levels, but one of the calibration sets was spiked with an internal standard (IS). The other two models were built with the serum pool from osteoporotic patients, which was spiked at different concentrations with the target analytes. In this case, one of the serum calibration sets was also spiked with the IS. The study shows that the IS allowed noticeable correction of matrix effects for some HETE isomers at certain concentration levels, while accuracy was decreased at low concentration (15ng/mL) of them. Therefore, characterization of the method has been properly completed at different concentration levels., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A method using dual process columns of Matrix Solid Phase Dispersion (MSPD) and Solid Phase Extraction (SPE) has been developed for extracting and cleaning-up of nine triazine herbicides (ametryn, atrazine, cyanazine, prometryn, propazine, simazine, simetryn, terbuthylazine and terbutryn) in seaweed samples. Under optimized conditions, samples were blended with 2g of octasilyl-derivatized silica (C8) and transferred into an SPE cartridge containing ENVI-Carb II/PSA (0.5/0.5 g) as a clean up co-sorbent. Then the dispersed sample was washed with 10 mL of n-hexane and triazines were eluted with 20 mL ethyl acetate and 5 mL acetonitrile. Finally the extract was concentrated to dryness, re-constituted with 1 mL methanol:water (1:1) and injected into the HPLC-DAD system. The linearity of the calibration curves was excellent in matrix matched standards, and yielded the coefficients of determination>0.995 for all the target analytes. The recoveries ranged from 75% to 100% with relative standard deviations lower than 7%. The achieved LOQs (<10 µg kg(-1)) for all triazines under study permits to ensure proper determination at the maximum allowed residue levels set in the European Union Legislation. Samples of three seaweeds were subjected to the procedure proving the suitability of MSPD method for the analysis of triazines in different seaweeds samples., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A combined strategy is here proposed for qualitative/quantitative targeted analysis of epoxyeicosatrienoic acids (EETs) in human serum. Identification of EET regioisomers was initially carried out by LC-TOF MS in high accuracy mode under optimum conditions for chromatographic separation of the four isomers with an isocratic method using 40:40:20 (v/v/v) methanol-acetonitrile-water containing 0.02% acetic acid. Confirmatory analysis was supported on MS/MS experiments using the hybrid QqTOF mass analyzer by targeted fragmentation of the precursor ion fitting with the molecular formula C₂₀H₃₂O₃ (319.2279 m/z). Identification of selective fragment ions in high accuracy mode enabled the localization of the epoxy functional group and, therefore, the assignation of chromatographic peaks to each EET isomer. After qualitative analysis, an automated method was developed for analysis of EETs in human serum by direct analysis using an on-line platform based on SPE-LC-QqQ MS/MS in selected reaction monitoring. Recovery factors estimated with a dual-cartridge configuration were above 87% for all metabolites either using non-spiked and spiked serum at three different concentrations. Precision, calculated as within-laboratory repeatability and expressed as relative standard deviation, ranged from 2.5 to 9.9% with detection limits below 0.15 ng mL(-1). The optimization of the method was completed with a stability study under different conditions to assess the suited conditions for analysis of EET intermediate metabolites. Finally, concentration ranges of EETs were measured in nine healthy individuals., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Four extraction techniques-namely, conventional maceration, ultrasound-assisted extraction, microwave-assisted extraction, and superheated liquid extraction (SHLE)-have been compared to evaluate their suitability to obtain valuable compounds from a raw material traditionally of scant interest: grape skin residues from ethanol-distillation. With this aim, red- and white-grape skins were separated from the rest of the pomace residue and subjected to extraction with 1:1 ethanol-acidic water as extractant in order to obtain the largest possible number of valuable compounds from this material, which has so far been used only as a heat source. The resulting extracts were characterized by the Folin-Ciocalteu and Ferric Reducing Antioxidant Power tests and by liquid chromatography-time-of-flight/mass spectrometry (LC-TOF/MS). The composition of the extracts under each of the optimal conditions was studied by LC-TOF/MS, and the information thus obtained compared by Venn diagrams. These diagrams, together with the extracted base peak chromatograms, were used to assess the optimal working conditions. Tentative identification of compounds was conducted using open-free databases. Grape skins from distillation industries are a source of compounds of interest for the food and nutraceutical fields., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The automated method developed for the determination of carotenoids uses 200 μL of serum, which was mixed with 400 μL of tetrahydrofuran, vortexed for 1 min, settled for 10 min, centrifuged for 6 min and the supernatant injected into an automatic solid-phase extraction (SPE) system for cleanup-preconcentration. A 10% water-acetonitrile mobile phase at 1.5 mL min(-1) eluted the retained compounds and transferred them on-line to a reversed-phase analytical column for individual separation of the target analytes. Visible detection was performed at 450 and 460 nm. The detection limits for the target analytes were between 3 and 30 ng mL(-1); the precision (expressed as relative standard deviation) ranged between 2.83 and 5.06% for repeatability and between 3.80 and 7.40% for within laboratory reproducibility. The total analysis time was 18 min. The proposed method is reliable, robust, and has an excellent potential for high-throughput use in both clinical and research laboratories., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Thermal Lens Spectrometry has traditionally been carried out in the single-beam and the mode-mismatched dual-beam configurations. Recently, a much more sensitive dual-beam TL setup was developed, where the probe beam is expanded and collimated. This feature optimizes Thermal Lens (TL) signal and allows the use of thicker samples, further improving the sensitivity. In this paper, we have made comparisons between the conventional and optimized TL configurations, and presented applications such as measurements of very low absorptions and concentrations in water and Cr(III) aqueous solution in the UV-vis range. For pure water we found linear absorption coefficients as low as the Raman scattering one due to the stretching vibrational modes of OH group. The detection limit was estimated 1 × 10(-6)cm(-1) with a 180-mW excitation power using a 100-mm cell length. This sensitivity is very high, considering that water has a photothermal enhancement factor ∼ 33 times smaller than CCl(4), for example. For Cr(III) species in aqueous solution, the limit of detection (LOD) was estimated in ∼ 40 ng mL(-1) at 514 nm, or ∼ 10 ng mL(-1) at 405 nm, which is ∼ 30 times smaller than the LOD achieved with conventional transmission techniques. The more recent TL configuration is very attractive to obtain absorption spectra, since the result does not depend critically on the beam parameters, unlike the other configurations. The main drawbacks of this optimized TL configuration are the longer acquisition time and the need for larger samples., (Copyright © 2011. Published by Elsevier B.V.)

The evidence that glyoxylate is a biomarker of tolerance or susceptibility to the action of herbicides belonging to the glycine family makes necessary to develop simple methods for the determination of this metabolite. Glyoxylate level allows both to know the presence/absence of members of the glycine family in plants and plant response to these herbicides. With this aim, a colorimetric-screening method has been developed for determination of glyoxylate based on formation of a phenylhydrazone, then oxidised to red coloured 1,5-diphenylformazan. Simultaneous optimization of ultrasound-assisted extraction of glyoxylate from plants and derivatization by a multivariate design has allowed the determination of the target analyte in fresh plants without interferences from pheophytines and compounds with carbonyl groups. Limits of detection and quantification are 0.05 μg ml(-1) and 0.17 μg ml(-1), respectively, with precision, expressed as relative standard deviation, of 3.3% for repeatability and 5.6% for the within-day laboratory reproducibility. Only 50mg of plant is necessary for determination of glyoxylate within 32 min. Confirmatory analysis by capillary electrophoresis-diode array detection in samples of Lolium spp. subjected to treatment with glyphosate shows that the relative error of the proposed method is always lower than 7%., (Copyright © 2010 Elsevier B.V. All rights reserved.)

The chemo-electrical properties of chitosan-carbon nanotubes (Chit-CNT) Conductive bio-Polymer nano-Composites (CPC) transducers processed by spray layer-by-layer (LbL) technique have been investigated. Results show that unlike most synthetic polymer matrices, chitosan provides the transducer with high sensitivity towards not only polar vapours like water and methanol but also to a lesser extent toluene. Quantitative responses are obtained, well fitted with the Langmuir-Henry-Clustering (LHC) model allowing to link electrical signal to vapour content. Chit-CNT transducers selectivity was also correlated with an exponential law to the inverse of Flory-Huggins interaction parameter chi(12). These properties make Chit-CNT a good transducer to be implemented in an e-nose. Additionally, the observation by atomic force microscopy (AFM) of Chit-CNT morphology suggests a chemical nano-switching mechanism promoting tunnelling conduction and originating macroscopic vapour sensing.

A method for fast and selective determination of the main triterpenic compounds present in olive leaves - oleanolic, ursolic and maslinic acids as triterpenic acids and, uvaol and erythrodiol as triterpenic dialcohols - is reported here. Quantitative isolation of the analytes has been accomplished in 5min by microwave assistance using ethanol as extractant. Due to the medium polarity of triterpenic acids and dialcohols, different ethanol-water ratios were tested in order to select the optimum extractant composition for their solubilisation. Microwave assistance provided a significant shortening of the leaching time as compared to conventional procedures by maceration, which usually requires at least 5h. After extraction, determination was carried out by liquid chromatography-tandem mass spectrometry (LC-MS-MS) with a triple quadrupole (qQq) mass detector without any clean-up step prior to chromatographic analysis. Highly selective identification of triterpenes was confirmed by multiple reaction monitoring (MRM) using the most representative transitions from the precursor ion to the different product ions, while the most sensitive transitions were used for MS-MS quantitation. Total analysis performed in 25 min enables the characterization of a fraction with particular interest in the pharmacological area.

A method for the extraction of valuable compounds from plants and flowers (viz. laurel, rosemary, thyme, oregano and tuberose) is proposed. The dynamic approach allows go-and-backward circulation of the extractant (ethanol) through the solid sample subjected to the action of an ultrasound probe (thus reducing sample amount and avoiding overpressure). A multivariate optimisation study and application of the optimum values of the variables to kinetics studies show that 10 min is sufficient to obtain extraction efficiencies that greatly surpass those provided by steam distillation for essential oils or superheated liquid extraction for these oils and other valuable compounds, with lower costs and higher quality of the extract. The extraction time of the proposed method is 176-165 min shorter than steam distillation and 31-20 min shorter than superheated liquid extraction, depending on the target compound.

This review intends to show analytical chemists a very little known application of ultrasound for sample preparation: that dealing with liquid samples. The influence of this type of energy on the development of chemical reactions (e.g. depolymerization, redox, esterification, alkylation, addition, ethylation of organometallic compounds, complex formation) and that on heterogeneous liquid-liquid processes (e.g. liquid-liquid extraction, homogenization, emulsification, liposome formation) deserves to be taken into consideration in the analytical laboratory in order to take profit from its versatile effects to improve, accelerate or make possible a given process.

A flow injection-pervaporation approach, where the samples--beech or olive leaves--were introduced as slurry, has been used for continuous derivatization hydride generation and separation of cadmium prior to determination by atomic absorption spectrometry. The removal of the analyte is achieved with an 1mol/l HCl+16% H(2)O(2) aqueous solution with the help of an ultrasound probe acting for 17 min. Thiourea and cobalt were also added to the slurry for kinetic catalysis of hydride generation. A CRM - beech leaves - where the analyte had not been certified but estimated was used for optimisation of the leaching step. The results obtained using direct calibration against aqueous standards demonstrated the reliability of the method. The linear concentration range of the calibration curve was from pg/ml to ng/ml, with a correlation coefficient, r(2), better than 0.99. The detection and quantification limits were 0.3 and 0.9ng/ml, respectively. The relative standard deviation for within-laboratory reproducibility was 5.7%. Olive leaves CRM was used for validation.

A method to determine organochlorine pesticides in horticultural samples (lettuce, tomato, spinach, potato, turnip leaf and green bean) using pressurized liquid extraction (PLE) is described and compared with microwave assisted extraction (MAE). Significant parameters affecting PLE procedure such as temperature, static extraction time and extraction solvent were optimised and discussed. Clean-up of extracts was performed by solid phase extraction (SPE) using a carbon cartridge as adsorbent. Pesticides were determined by gas chromatography and electron capture detection (GC-ECD). Analytical recoveries obtained were ca. 100% and the relative standard deviations were lower than 15% for most of the studied pesticides with the proposed methods in each analysed matrix.

A study of ancient coins with different corrosion degrees and the same or different composition has been carried out by using energy-dispersive X-ray fluorescence spectrometry (XRFS) and laser-induced break-down spectroscopy (LIBS). The results obtained show the complementarity of both techniques: XRFS provides information about the superficial composition which is used for the assignation of atomic lines in LIBS, and this provides in-depth and tomographic information. Thus, some very superficial impurities such as Ag, Cl, Au, Sr and Sb are only detected by XRFS, while highly corroded coins of iron-based alloy provided no iron signal by XRFS but increased concentration of this element up to constant composition by LIBS by increasing the shot number. The average of the same laser-shot number for all sampling positions of a sampling zone produces a significant improvement of the signal-to-noise ratio (SNR) in the detriment of punctual information as that obtained by single-position kinetic series.

Superheated hexane extraction has been tested for obtaining fatty acids from grape seed and compared with conventional Soxhlet and hot hexane extractions. Seeds from grape residues from a winery were dried for 46h at 105 degrees C, milled and sieved by particle size (d<0.42mm, 0.420.84mm). An optimization study of influential variables on superheated hexane extraction (namely extraction time, temperature, pression, particle size and sample amount) was carried out by a multivariate approach. All the extracts were concentrated in a rotary evaporator and dried by adding 1g of Na(2)SO(4). Then, 2ml of the dried extract were subjected to reaction with 1ml of a 0.5M solution of sodium methylate in methanol to obtain fatty acid methyl esters (FAMEs). After derivatization, FAMEs were quantified by GC-FID. The results show that the optimal conditions for superheated hexane extraction are: time extraction, 10min; temperature, 80 degrees C; pressure, 40bar; particle size, d<0.42mm; amount of sample, 0.4g. Under these conditions, around 84% of the fatty acids (out of the amount obtained by Soxhlet extraction) is extracted. Comparison with Soxhlet and hot hexane extractions showed that the percentages of FAMEs are similar in all the extracts and they agree with the data in the bibliography.

A study of the statistic characteristics of the multidetermination of several enological parameters - namely, alcoholic degree, volumic mass, total acidity, glycerol, total polyphenol index, lactic acid and total sulphur dioxide - depending on the spectroscopic zone employed, was carried out. The two techniques used were near infrared spectroscopy (NIRS) and Fourier transform mid infrared spectroscopy (FT-MIRS). The combination of these two regions (sum of their spectra) was also studied. NIRS yielded better results, but the use of both zones improved the determination of glycerol and total sulphur dioxide. The training and validation sets used for developing general equations were built with samples from different apellation d'origine, different wine types, etc. Partial least squares regression was used for multivariate calibration, using systematic cross validation in the calibration stage and external validation in the testing stage. Sample preparation was not required.

The aim of the present study is to accelerate the acid-digestion step needed for the study of proteinaceous binding media by gas chromatography. The optimisation of the digestion step was carried out using full and half-fractioned factorial designs. The evaluation of the precision of the proposed digestion method and its comparison with the method considered as the reference showed the high irreproducibility of the derivatisation reaction needed for the analysis of the amino acids by gas chromatography. Although the optimal digestion time was found to be 90min, the differences between different irradiation times were statistically non-significant, so an extremely high reduction on the analysis time is achieved.

An approach for automated fast extraction of the fat content in bakery products based on focused microwave-assisted Soxhlet extraction (FMASE) and gravimetric determination is proposed. The main factors affecting the extraction efficiency namely; power of irradiation, number of cycles and irradiation time were optimized using experimental design methodology. The proposed method was applied to six samples, which were classified in two groups namely snacks and cookies. The results obtained agree with those provided by the AOAC 920.39 reference extraction method. No significant differences in the extraction efficiency of the fat content in bakery samples using FMASE versus the official method were found. Moreover, a drastic reduction in both the extraction time (60 and 35min versus 16 and 8h, respectively, for the two above commented groups) and sample handling are achieved with similar precision (expressed as repeatability and within laboratory reproducibility standard deviation) to that provided by the AOAC 920.39 method. In addition, the proposed method is cleaner than the reference method as 75-80% of the extractant is recycled.