Genetic variants of antioxidant enzymes and environmental exposures as molecular biomarkers associated with the risk and aggressiveness of bladder cancer.

Bladder cancer (BC) is one of the top 10 most common tumours worldwide; however, no molecular markers are currently available for tumour management and follow-up. BC could benefit from molecular biomarkers in environmental disease, which provide mechanistic understanding of individual susceptibility to exposure-related cancers and allow characterizing genetic alterations in the molecular pathway for malignancy. This case-control study performed a molecular analysis in 99 BC and 125 controls. Buccal swabs were collected to assess SNPs in eleven genes coding for xenobiotic detoxification enzymes, cellular antioxidant defences, and hormone synthesis and signalling (NAT2 (rs1801280), GPX1 (rs1050450 and rs17650792), TXNRD1 (rs7310505), PRDX3 (rs3740562), PON1 (rs662), SOD1 (rs10432782), SOD2 (rs4880), CAT (rs1001179), CYP17A1 (rs743572) and ESR1 (rs746432)). A structured questionnaire was administered to study participants to assess environmental and dietary chemical exposures. Several miRNAs associated with BC and detoxification/antioxidant pathways were analysed in a subsample of the study population, including miR-93-5p, miR-221-3p, miR-126, miR-27a-3p, miR-193b, and miR-193a-5p. Levels of selected environmental pollutants (polycyclic aromatic hydrocarbons and endocrine disrupting chemicals) were determined in urine from a subsample of BC cases and controls. We found that CYP17A1, CAT, SOD1, ESR1, PON1, and GPX1 (rs17650792) were associated with BC risk. Furthermore, exposure to smoke and/or dust, and alcohol intake were identified as risk factors for BC. Increased urinary levels of benzo[a]pyrene and bisphenol A were observed in BC patients relative to controls, along with an increased expression of miR-193b, miR-27a and miR-93-5p in BC. Nevertheless, further studies with a larger sample size are warranted to confirm these exploratory results. This study also shows that the combination of genetic markers (PON1 and CYP17A1) and miRNA (miR-221-3p and miR-93-5p) open a new scenario in the use of non-invasive biomarkers in the stratification of BC to guide personalized medicine, which is extremely urged in the current clinical setting.

Chromatographic Methods for the Determination of Emerging Contaminants in Natural Water and Wastewater Samples: A Review.

This review is devoted to analytical methods published in the scientific literature in the last 10 years for the determination of emerging contaminants in aquatic media. The article is mainly focused on sample preparation and on instrumental techniques most used for the detection and quantification of the analytes of interest. The sample preparation techniques include classical liquid-liquid extraction and solid-phase extraction, but also recent microextraction techniques such as solid-phase microextraction, stir-bar sorptive extraction, dispersive liquid-liquid microextraction, ultrasound-assisted emulsification microextraction, or microextraction by packed sorbent. Most studies focus on minimizing the number of analysis steps and on the use of the lowest amount of solvents in the sample treatment step. Liquid chromatography and gas chromatography mainly coupled to tandem mass spectrometry are usually the employed analytical techniques. A large number of multiresidue methods are being developed for the determination of several families of these compounds with only one extraction step to minimize sample handling and treatment.

Liquid chromatography-electrochemical detection for the determination of ethoxyquin and its dimer in pear skin and salmon samples.

Ethoxyquin (EQ) is widely used as a synthetic antioxidant in animal feed, an antiscalding agent in apples and pears and as a color preservative in some spices. Since the presence of EQ in food products could cause negative health effects it is necessary to develop reliable analytical methods to evaluate the risk of human exposure. In this work, a sensitive, selective and accurate method based on solid-liquid extraction followed by clean-up with solid sorbent and liquid chromatography-electrochemical detection analysis with boron doped diamond electrode (LC-EC) for the determination of ethoxyquin and its dimer (EQDM) in pear skin and salmon samples, was developed. The method was validated according to the European Commission guidelines. The main variables of extraction were accurately optimized. The amounts of solid sorbents for clean-up procedure were optimized by using experimental design. A Box-Behnken design to obtain the optimum conditions was applied. For validation, a matrix-matched calibration was established and a recovery assay with spiked samples was carried out. The limits of detection (LODs) found were 0.05 and 0.1mgkg-1 for EQ and its dimer, respectively. The precision (as relative standard deviation, RSD) was lower than 15% with recoveries of compounds close to 100% in spiked samples.

Determination of bisphenols with estrogenic activity in plastic packaged baby food samples using solid-liquid extraction and clean-up with dispersive sorbents followed by gas chromatography tandem mass spectrometry analysis.

Bisphenols (BPs) are a family of chemicals with known endocrine disrupting activity. Bisphenol A (BPA) is the most representative prototype of this group of chemicals. Recently, the use of BPA, a prototype of endocrine disruptors, has been reduced and replaced with structural analogs due to its negative effects on both the environment and consumers. In this work, a new method is presented for the determination of seven BPs, with estrogenic activity in ready-to-eat plastic packaged baby foods. The procedure involves the isolation of the analytes using solid-liquid phase extraction with acetonitrile followed by a clean-up step with a mixture of dispersive-SPE sorbents (C18 and PSA) and magnesium sulphate, to reduce matrix effect from proteins, sugars and lipids. Extraction parameters were optimized using multivariate optimization methods. The compounds were detected and quantified by gas chromatography tandem mass spectrometry (GC-MS/MS). The limits of quantification were between 0.1 and 1.2ngg-1 for the studied analytes. The method was validated using matrix-matched calibration and recovery assays with spiked samples. Recovery rates were between 91% and 110% and % RSD was lower than 13% in all cases. The method has been successfully applied for the determination of these endocrine disrupting chemicals (EDCs) in samples of a novel type of food consumed by pre-schoolers. This is the first study to analyze EDCs in plastic packaged foods consumed by this target group.

Multiclass method for the determination of pharmaceuticals and personal care products in compost from sewage sludge using ultrasound and salt-assisted liquid-liquid extraction followed by ultrahigh performance liquid chromatography-tandem mass spectrometry analysis.

An analytical method for the analysis of 16 pharmaceuticals and personal care products in compost from sewage sludge is successfully validated. Ultrasound assisted extraction with a mixture of acetonitrile:ethyl acetate (1:1, v/v) containing 10% (v/v) of acetic acid was carried out. Two cycles of extraction of 10min were applied. A clean-up of the extracts using salt-assisted liquid-liquid extraction (SALLE) was also included. Experimental design was used for the optimization of the main parameters involved in the extraction and cleaned-up steps. The chromatographic separation was carried out by ultrahigh performance liquid chromatography using a mobile phase gradient mixture of a 13mM buffer ammonium formate solution (pH 9.25) (solvent A) and methanol (solvent B). An ACQUITY UPLC® BEH C18 column (1.7µm; 2.1×50mm) column was used. Analytes were separated in less than 11min. The compounds were detected and quantified using single reaction monitoring electrospray tandem mass spectrometry. The limits of detection calculated ranged from 0.5 to 4ngg-1d.w., and the limits of quantification from 2 to 13ngg-1d.w. Recoveries from 93% to 111%, with relative standar deviations lower than 11% in all cases, were obtained. The method was applied to natural compost samples. High concentrations of some analytes were found. Ketoprofen (510ngg-1d.w.), methylparaben (240ngg-1d.w.), diclofenac (175ngg-1d.w.) and flufenamic acid (128ngg-1d.w.) were the most abundant.

A novel method for the determination of glycidyl and 3-monochloropropanediol esters in fish oil by gas chromatography tandem mass spectrometry.

Today, food security is one of the most important global issues with food quality control and identification of contaminants in foods and beverages, being crucial for human health and safety. In this paper, a novel single-step method for the simultaneous determination of 3-monochloropropanediol (3-MCPD) and glycidyl esters in samples of winterized and non-winterized fish oil by using gas chromatography tandem mass spectrometry (GC-MS/MS) is validated. The method is based on alkaline hydrolysis of esters at room temperature, using only 3-MCPD-d5 as internal standard, and a derivatization step with phenylboronic acid (PBA) at 90°C. The use of GC-MS/MS results in a simplified sample treatment and improvement of the limits of quantification and precision of the analytical method with no need of additional concentration of the extracts. A backflush tee placed between two HP-5 MS UI columns (15m×0.25µm×0.25mm) was used in order to minimize matrix effects and peak shape degradation usually observed in routine analyses. The method was validated in winterized and non-winterized fish oil, achieving a limit of quantification of 100ngg-1 and 50ngg-1 for 3-MCPD and glycidol, respectively. Method validation was accomplished by comparing our laboratory results with results obtained by an accredited reference laboratory (SGS Germany GmbH) and by calculating the recoveries obtained in an assay with spiked samples. For glycidol quantification, a mathematical equation was developed in order to compensate for the partial conversion of 3-MCPD into glycidol. This expression involves the quantification of 3-MBPD-d5 generated during hydrolysis reaction.

Multi-residue analysis of 36 priority and emerging pollutants in marine echinoderms (Holothuria tubulosa) and marine sediments by solid-liquid extraction followed by dispersive solid phase extraction and liquid chromatography-tandem mass spectrometry analysis.

Marine echinoderms are filter-feeding invertebrates widely distributed along the coasts, and which are therefore extensively exposed to anthropogenic xenobiotics. They can serve as good sentinels for monitoring a large variety of contaminants in marine ecosystems. In this context, a multi-residue analytical method has been validated and applied to Holothuria tubulosa specimens and marine sediments for the determination of 36 organic compounds, which belong to some of the most problematic groups of emerging and priority pollutants (perfluoroalkyl compounds, estrogens, parabens, benzophenones, plasticizers, surfactants, brominated flame retardants and alkylphenols). Lyophilization of samples prior to solvent extraction and clean-up of extracts with C18, followed by liquid chromatography-tandem mass spectrometry analysis, is proposed. A Box-Behnken design was used for optimization of the most influential variables affecting the extraction and clean-up steps. For validation, matrix-matched calibration and recovery assay were applied. Linearity (% r2) higher than 99%, recoveries between 80% and 114% (except in LAS and NP1EO), RSD (precision) lower than 15% and limits of quantification between 0.03 and 12.5ngg-1 dry weight (d.w.) were achieved. The method was applied to nine samples of Holothuria collected along the coast of Granada (Spain), and to marine sediments around the animals. The results demonstrated high bioaccumulation of certain pollutants. A total of 25 out of the 36 studied compounds were quantified, being surfactants, alkylphenols, perfluoroalkyl compounds, triclocarban and parabens the most frequently detected. Nonylphenol was found in the highest concentration (340 and 323ngg-1 d.w. in sediment and Holothuria samples, respectively).

Sorption, degradation and transport phenomena of alcohol ethoxysulfates in agricultural soils. Laboratory studies.

In the present work, laboratory studies were conducted in order to determine and model the sorption, degradation and transport processes of alcohol ethoxysulfates (AES), one of the most important groups of anionic surfactants. Adsorption/desorption isotherms were obtained for several structurally related AES ethoxymers (homologue AES-C12En with n = 0-10 ethoxymer units and homologue AES-C14En with n = 0-7 ethoxymer units) using a batch equilibrium method. Data were fitted to a linear and a Freundlich isotherm models. Additionally, experiments in continuous-flow soil columns were also carried out and the breakthrough curves observed for each compound were studied. Breakthrough curves were used to determine the fundamental parameters of the transport model (hydrodynamic dispersion coefficient, degradation rate constant and adsorption/desorption isotherm slope), that is the main phenomena that take place simultaneously when AES move through agricultural soil. When the results obtained for the AES ethoxymers are combined, they reveal a clear and consistent trend towards a sorption increase with the number of ethoxylated units and with the length of the alkyl chain that opens the possibility to estimate the values of the transport parameters for other structurally related ethoxymers.

Biomonitoring of 21 endocrine disrupting chemicals in human hair samples using ultra-high performance liquid chromatography-tandem mass spectrometry.

Rapid industrial growth has increased human exposure to a large variety of chemicals with adverse health effects. These industrial chemicals are usually present in the environment, foods, beverages, clothes and personal care products. Among these compounds, endocrine disrupting chemicals (EDCs) have raised concern over the last years. In the present work, the determination of 21 EDCs in human hair samples is proposed. An analytical method based on the digestion of the samples with a mixture of acetic acid/methanol (20:80, v/v) followed by a solid-liquid microextraction and analysis by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was developed and validated. The most influential parameters affecting the extraction method were optimized. The method was validated using matrix-matched calibration and recovery assays. Limits of detection ranged from 0.2 to 4 ng g-1, limits of quantification from 0.5 to 12 ng g-1, and inter- and intra-day variability was under 15% in all cases. Recovery rates for spiked samples ranged from 92.1 to 113.8%. The method was applied for the determination of the selected compounds in human hair. Samples were collected weekly from six randomly selected volunteers (three men and three women) over a three-month period. All the analyzed samples tested positive for at least one of the analyzed compounds.

Validated method for the determination of perfluorinated compounds in placental tissue samples based on a simple extraction procedure followed by ultra-high performance liquid chromatography-tandem mass spectrometry analysis.

Xenobiotic exposure during pregnancy is inevitable. Determination of perfluorinated compounds (PFCs), chemicals described as environmental contaminants by Public Health Authorities due to their persistence, bioaccumulation and toxicity, is a challenge. In the present work, a method based on a simplified sample treatment involving freeze-drying, solvent extraction and dispersive clean-up of the extracts using C18 sorbents followed by an ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis was developed and validated for the determination of five perfluorinated carboxylic acids (C4-C8) and perfluorooctane sulfonate (PFOS) in placental tissue samples. The most influential parameters affecting the extraction method and clean-up were optimized using Design of Experiments (DOE). The method was validated using matrix-matched calibration. Found limits of detection (LODs) ranged from 0.03 to 2 ng g(-1) and limits of quantification (LOQs) from 0.08 to 6 ng g(-1), while inter- and intra-day variability was under 14% in all cases. Recovery rates for spiked samples ranged from 94% to 113%. The method was satisfactorily applied for the determination of compounds in human placental tissue samples collected at delivery from 25 randomly selected women.

Determination of selected parabens, benzophenones, triclosan and triclocarban in agricultural soils after and before treatment with compost from sewage sludge: A lixiviation study.

An accurate and sensitive method for the determination of selected EDCs in soil and compost from wastewater treatment plants is developed and validated. Five parabens, six benzophenone-UV filters and the antibacterials triclosan and triclocarban were selected as target analytes. The parameters for ultrasound-assisted extraction were thoroughly optimized. After extraction, the analytes were detected and quantified using ultra-high performance liquid chromatography tandem mass spectrometry. Ethylparaben (ring-(13)C6 labelled) and deuterated benzophenone (BP-d10) were used as internal standards. The method was validated using matrix-matched calibration and recovery assays with spiked samples. The limits of detection ranged from 0.03 to 0.40 ng g(-1) and the limits of quantification from 0.1 to 1.0 ng g(-1), while precision in terms of relative standard deviation was between 9% and 21%. Recovery rates ranged from 83% to 107%. The validated method was applied for the study of the behavior of the selected compounds in agricultural soils treated and un-treated with compost from WWTP. A lixiviation study was developed in both agricultural soil and treated soil and first order kinetic models of their disappearance at different depths are proposed. The application of organic composts in the soil leads to an increase of the disappearance rate of the studied compounds. The lixiviation study also shows the risk of pollution of groundwater aquifers after disposal or waste of these EDCs in agricultural soils is not high.

Improved sample treatment for the determination of fructooligosaccharides in milk related products by liquid chromatography with electrochemical and refractive index detection.

A simple and reliable method for the determination of the fructooligosaccharides (FOS) kestose (GF2), nystose (GF3), fructofuranosylnystose (GF4), in the presence of fructose, glucose and lactose in dairy products is proposed. The most relevant advantages of the proposed method are the simultaneous determination of the most common FOS in enriched products and a reduction of the time required for sample treatment since the method consists merely in addition of a precipitation solution for the removal of lipids and proteins. Furthermore, the method saves a substantial amount of reagents compared with other methods and sample manipulation is reduced. Two chromatographic separations are proposed. The first one is carried out on an amino phase column for liquid chromatography with refractive index detection (HPLC-RI) (concentration of analytes higher than 0.1 mg mL(-1)) and the second one on an anion-exchange Carbopac PA-1 column for high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) (concentration of FOS lower than 0.1 mg mL(-1)). The method was validated by recovery assays with spiked samples using matrix-matched calibration. The limits of quantification of the method ranged from 1.2 to 2.0 µg mL(-1) for HPAEC-PAD and from 140 to 200 µg mL(-1) for HPLC-RI, while inter- and intra-day variability was under 3.5% in all cases. The proposed method was applied to the determination of compounds in supplemented milk, infant formulas and milk related juices with good recoveries in all cases.

Analytical methods for the assessment of endocrine disrupting chemical exposure during human fetal and lactation stages: a review.

In the present work, a review of the analytical methods developed in the last 15 years for the determination of endocrine disrupting chemicals (EDCs) in human samples related with children, including placenta, cord blood, amniotic fluid, maternal blood, maternal urine and breast milk, is proposed. Children are highly vulnerable to toxic chemicals in the environment. Among these environmental contaminants to which children are at risk of exposure are EDCs -substances able to alter the normal hormone function of wildlife and humans-. The work focuses mainly on sample preparation and instrumental techniques used for the detection and quantification of the analytes. The sample preparation techniques include, not only liquid-liquid extraction (LLE) and solid-phase extraction (SPE), but also modern microextraction techniques such as extraction with molecular imprinted polymers (MIPs), stir-bar sorptive extraction (SBSE), hollow-fiber liquid-phase microextraction (HF-LPME), dispersive liquid-liquid microextraction (DLLME), matrix solid phase dispersion (MSPD) or ultrasound-assisted extraction (UAE), which are becoming alternatives in the analysis of human samples. Most studies focus on minimizing the number of steps and using the lowest solvent amounts in the sample treatment. The usual instrumental techniques employed include liquid chromatography (LC), gas chromatography (GC) mainly coupled to tandem mass spectrometry. Multiresidue methods are being developed for the determination of several families of EDCs with one extraction step and limited sample preparation.

Analysis of 17 neurotransmitters, metabolites and precursors in zebrafish through the life cycle using ultrahigh performance liquid chromatography-tandem mass spectrometry.

An ultrahigh performance liquid chromatography-tandem mass spectrometry method for the identification and quantification of neurotransmitters, metabolites and precursors at different stages in zebrafish life was developed. Betaine, glutamine, glutamic acid, γ-aminobutyric acid, phosphocholine, glycerophosphocholine, cytidine 5'-diphosphocholine, choline, acetylcholine, dopamine, norepinephrine, serotonin, tyrosine, epinephrine, tryptophan, 5-hydroxyindolacetic acid and agmatine were selected as analytes. The method consisted of a simple deproteinization of samples using methanol and formic acid, subsequent injection onto the chromatographic equipment and quantification with a triple quadrupole mass spectrometer detector using an electrospray ionization interface in positive mode. Limits of detection ranged from 0.02 to 11ngmL(-1) and limits of quantification from 0.1 to 38ngmL(-1), depending on the analyte. The method was validated according to US Food and Drugs Administration (FDA) guideline for bioanalytical assays. Precision, expressed as relative standard deviation (%RSD), was lower than 15% in all cases, and the determination coefficient (R(2)) was equal or higher than 99.0% with a residual deviation for each calibration point lower than ±25%. Mean recoveries were between 85% and 115%. The method was applied to determine of these compounds in zebrafish from early stages of development to adulthood and showed the time-course of neurotransmitters and others neurocompounds through the life cycle. The possibility of measuring up to 17 compounds related with the main neurotransmitter systems in a simple analytical method will complement and reinforce the use of zebrafish in multiple applications in the field of neurosciences. The proposed method will facilitate future studies related with brain development.

Wide-range and accurate modeling of linear alkylbenzene sulfonate (LAS) adsorption/desorption on agricultural soil.

In this paper, rigorous data and adequate models about linear alkylbenzene sulfonate (LAS) adsorption/desorption on agricultural soil are presented, contributing with a substantial improvement over available adsorption works. The kinetics of the adsorption/desorption phenomenon and the adsorption/desorption equilibrium isotherms were determined through batch studies for total LAS amount and also for each homologue series: C10, C11, C12 and C13. The proposed multiple pseudo-first order kinetic model provides the best fit to the kinetic data, indicating the presence of two adsorption/desorption processes in the general phenomenon. Equilibrium adsorption and desorption data have been properly fitted by a model consisting of a Langmuir plus quadratic term, which provides a good integrated description of the experimental data over a wide range of concentrations. At low concentrations, the Langmuir term explains the adsorption of LAS on soil sites which are highly selective of the n-alkyl groups and cover a very small fraction of the soil surface area, whereas the quadratic term describes adsorption on the much larger part of the soil surface and on LAS retained at moderate to high concentrations. Since adsorption/desorption phenomenon plays a major role in the LAS behavior in soils, relevant conclusions can be drawn from the obtained results.

New method for the determination of parabens and bisphenol A in human milk samples using ultrasound-assisted extraction and clean-up with dispersive sorbents prior to UHPLC-MS/MS analysis.

A sensitive and accurate analytical method for the determination of methyl-, ethyl-, propyl- and butylparaben and bisphenol A in human milk samples has been developed and validated. The combination of ultrasound-assisted extraction (UAE) and a simplified and rapid clean-up technique that uses sorbent materials has been successfully applied for the preparation of samples prior to ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis. The analytes were extracted from freeze-dried human milk samples using acetonitrile and ultrasonic radiation (three 15-min cycles at 70% amplitude), and further cleaned-up with C18 sorbents. The most influential parameters affecting the UAE method and the clean-up steps were optimized using design of experiments. Negative electrospray ionization (ESI) in the selected reaction monitoring (SRM) mode was used for MS detection. The use of two reactions for each compound allowed simultaneous quantification and identification in one run. The analytes were separated in less than 10min. Deuterium-labeled ethylparaben-d5 (EPB-d5) and deuterium-labeled bisphenol A-d16 (BPA-d16) were used as surrogates. The limits of quantification ranged from 0.4 to 0.7ngmL(-1), while inter- and intra-day variability was under 11.1% in all cases. In the absence of certified reference materials, recovery assays with spiked samples using matrix-matched calibration were used to validate the method. Recovery rates ranged from 93.8% to 112.2%. The proposed method was satisfactorily applied for the determination of four selected parabens and bisphenol A in human milk samples obtained from nursing mothers living in the province of Granada (Spain).

Quantification of ß-hydroxymethylbutyrate and leucine by ultrahigh performance liquid chromatography tandem mass spectrometry at different situations and stages of a rodent life.

The main objective of this work was to develop a method to measure Leucine (Leu) and ß-hydroxymethylbutyrate (HMB) at basal levels in serum, urine, milk and brain microdialysates in rats. Ultrahigh performance liquid chromatography-electrospray-tandem mass spectrometry (UHPLC-ESI-MS/MS) was used as analytical technique. The sample treatment was simple and consisted of dilution with methanol and centrifugation for serum and urine, dilution with water and filtration with an Amicon filter for milk, and treatment with formic acid with no further dilution for microdialyzates. The procedures for sampling and the UHPLC-MS/MS parameters were accurately optimized to achieve the highest recoveries and to enhance the analytical characteristics of the method. For chromatographic separation, an Acquity UPLC BEH Amide column using acetonitrile-water gradient with formic acid as additive was used. The total run time was 4min. The analytical characteristics (accuracy, selectivity and sensitivity) of the proposed method were evaluated. The limits of detection (LODs) obtained ranged from 0.4 to 7ngmL(-1) and the limits of quantification (LOQs) from 1 to 22ngmL(-1). Precision, expressed as relative standard deviation (% RSD), was lower than 15% in all cases, and the determination coefficient (R(2)) was equal or higher than 99.0% with a residual deviation for each calibration point lower than ±25%. Mean recoveries were between 85 and 115%. The method was successfully applied to these matrices being able to detect significant differences between physiological situations, strains and stages of life.

Improved sample treatment for the determination of 17 strong sorbed quinolone antibiotics from compost by ultra high performance liquid chromatography tandem mass spectrometry.

The use of compost from sewage sludge for agricultural application is nowadays increasing, since composting is recognized as one of the most important recycling options for this material, being a source of nutrients for plants but also of contamination by persistent pollutants. In the present work, a multi-residue analytical method for the determination of 17 quinolone antibiotic residues in compost using multivariate optimization strategies and ultra high performance liquid chromatography-tandem mass spectrometry has been developed. It is based on the use of microwave-assisted extraction at drastic conditions with ACN:m-phosphoric acid (1% w/v) for 5 min at 120°C, in order to achieve a quantitative extraction of the compounds (>76% of extraction recovery). Extracts were cleaned-up by salt-assisted liquid-liquid extraction (SALLE) with NaCl at pH 1.5 (with HClO4) and then using a dispersive sorbent (PSA). After LC separation, the MS conditions, in positive electrospray ionization mode (ESI), were individually optimized for each analyte to obtain maximum sensitivity in the selected reaction monitoring mode (SRM). The analytes were separated in less than 7 min. Cincophen was used as surrogate standard. The limits of detection ranged from 0.2 to 0.5 ng g(-1), and the limits of the quantification from 0.5 to 1.5 ng g(-1), while intra- and inter-day variability (% RSD) was under 7% in all cases. A recovery assay was performed with spiked samples. Recoveries ranging from 95.3% to 106.2% were obtained. Cleanup procedure reduced significantly matrix effects, which constitutes an important achievement, considering the important drawbacks of matrix components in quality and validation parameters. This method was applied to several commercial compost samples. Only 6 of the studied antibiotics were not detected in any of the samples. The antibiotics with the highest concentrations were ciprofloxacin (836 ng g(-1)), ofloxacin (719 ng g(-1)), and enrofloxacin (674 ng g(-1)), which were also the only ones found in all the analyzed samples. The results showed that this method could also be potentially adapted for the analysis of other strong sorbed basic pharmaceuticals in solid environmental matrices.

Evaluation of Linear Alkylbenzene Sulfonate (LAS) behaviour in agricultural soil through laboratory continuous studies.

The behaviour of Linear Alkylbenzene Sulfonate (LAS) in agricultural soil is investigated in the laboratory using continuous-flow soil column studies in order to simultaneously analyze the three main underlying phenomena (adsorption/desorption, degradation and transport). The continuous-flow soil column experiments generated the breakthrough curves for each LAS homologue, C10, C11, C12 and C13, and by adding them up, for total LAS, from which the relevant retention, degradation and transport parameters could be estimated, after proposing adequate models. Several transport equations were considered, including the degradation of the sorbate in solution and its retention by soil, under equilibrium and non-equilibrium conditions between the sorbent and the sorbate. In general, the results obtained for the estimates of those parameters that were common to the various models studied (such as the isotherm slope, first order degradation rate coefficient and the hydrodynamic dispersion coefficient) were rather consistent, meaning that mass transfer limitations are not playing a major role in the experiments. These three parameters increase with the length of the LAS homologue chain. The study will provide the underlying conceptual framework and fundamental parameters to understand, simulate and predict the environmental behaviour of LAS compounds in agricultural soils.