Fast and sensitive determination of per- and polyfluoroalkyl substances in seawater.

In this work, a novel, fast, and sensitive method was developed for perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS) and PFOS precursor's determination in seawater. The proposed method consists in a vortex-assisted liquid-liquid microextraction (VALLME) combined with liquid chromatography (LC) and LTQ-Orbitrap high resolution mass spectrometry (LTQ-Orbitrap HRMS) determination. Several parameters affecting both the HPLC-LTQ Orbitrap HRMS determination and the VALLME were studied, with special attention to blank contamination problem. The use of LTQ-Orbitrap-HRMS in full mode, quantifying the target analytes using the exact mass, provides a very powerful detection in terms of sensitivity and specificity maintaining all the information provided by the full mass spectra, allowing, also, the identification of non-target substances. The use of matrix-matched calibration, together with labelled surrogate standards, minimize matrix effects and compensate potential recovery losses, resulting in recoveries between 95 and 105%, with excellent sensitivity (quantitation limit between 0.7 and 6 ng L-1) and precision (4-10%). The proposed method requires only 35 mL of sample and 100 µL of extracting solvent, is fast and avoids the use of other solvents to obtain the dispersive cloudy solution, simplifying the procedure and improving the existing procedures for the determination of per- and polyfluoroalkyl substances (PFASs) in seawater in terms of green analytical chemistry. The method was successfully validated by participating in a proficiency test assay provided by the National Measurement Institute of the Australian Government for the determination of PFOA, total PFOS and linear PFOS in waters. A revision of the state of the art in the last twelve years of methods for the analysis of PFASs in seawater and other types of water was performed, and a critical comparison between the developed method and the previously published was included. Finally, the method was applied to the analysis of samples from Ría de Vigo, a sensitive and semiconfined coastal area located in the northwest of Spain. PFOS, N-methyl perfluorooctanesulfonamide (n-MeFOSA) and N-ethyl perfluorooctanesulfonamide (n-EtFOSA) were detected in samples at levels lower than the maximum allowable concentration (MAC) established by Directive 2013/39/EU, but above the annual average (AA) levels.

Evergreen or deciduous trees for capturing PAHs from ambient air? A case study.

Tree canopies play a key role in the cycling of polycyclic aromatic hydrocarbons (PAHs) in terrestrial ecosystems, as leaves can capture PAHs from the air. In this study, accumulation of PAHs was compared in an evergreen species, P. pinaster, and in a deciduous species, Q. robur, in relation to some physio-morphological characteristics. For this purpose, pine needles and oak leaves collected from different sites across Galicia (NW Spain) were analysed to determine PAH contents, specific leaf area, stomatal density and conductance. Leaves and needles contained similar total amounts of PAHs. The major contribution of particle-bound PAHs in oak (the concentrations of 4- and 5-ring PAHs were two times higher, and those of 6-ring PAHs five times higher in oak than in pine) may be related to the higher specific leaf area (13 and 4 cm2 g-1 dry mass in respectively oak and pine). However, the major contribution of vapor-phase PAHs in pines may be affected by the stomatal conductance (two times higher in pine than in oak). Moreover, an increase in the diameter at breast height of trees led to an increase in accumulation of PAHs, with pine capturing higher amounts of low and medium molecular weight PAHs. The study findings underline the potential role of trees in improving air quality, taking into account the canopy biomass and life cycle.

Matrix solid phase dispersion method for determination of polycyclic aromatic hydrocarbons in moss.

In this work a matrix solid-phase dispersion extraction method, followed by programmed temperature vaporization-gas chromatography-tandem mass spectrometry determination is proposed for the analysis of polycyclic aromatic hydrocarbons (PAHs) in moss samples. A devitalized, cultivated Sphagnum palustre L. moss clone obtained from the "Mossclone" EU-FP7 Project was used for the optimization and validation of the proposed method. Good trueness (84-116%), precision (intermediate precision lower than 11%) and sensitivity (quantitation limits lower than 1.7ngg(-1)) were obtained. The proposed method was compared with other procedures applied for this complex matrix, achieving a considerable reduction of sample amount, solvent volume and time consumption. The procedure was successfully tested for the analysis of PAHs in exposed moss clone samples for the monitoring of air pollution. Finally, the method was also tested for its suitability in the analysis of PAHs in other moss species as well as a lichen species.

Proposal of a procedure for the analysis of atmospheric polycyclic aromatic hydrocarbons in mosses.

A useful analytical procedure for the analysis of 19 polycyclic aromatic hydrocarbons (PAHs) in moss samples using microwave assisted extraction and programmed temperature vaporization-gas chromatography-tandem mass spectrometry (PTV-GC-MS/MS) determination is proposed. The state of art in PAHs analysis in mosses was reviewed. All the steps of the analysis were optimized regarding not only to the analytical parameters, but also the cost, the total time of analysis and the labour. The method was validated for one moss species used as moss monitor in ambient air, obtaining high recoveries (between 83-108%), low quantitation limits (lower than 2 ng g(-1)), good intermediate precision (relative standard deviation lower than 10%), uncertainties lower than 20%. Finally, the method was checked for other species, demonstrating its suitability for the analysis of different moss species. For this reason the proposed method can be helpful in air biomonitoring studies.

Arsenic species determination in human scalp hair by pressurized hot water extraction and high performance liquid chromatography-inductively coupled plasma-mass spectrometry.

Analytical methods for the determination of total arsenic and arsenic species (mainly As(III) and As(V)) in human scalp hair have been developed. Inductively coupled plasma-mass spectrometry (ICP-MS) and high performance liquid chromatography (HPLC) coupled to ICP-MS have been used for total arsenic and arsenic species determination, respectively. The proposed methods include a "green", fast, high efficient and automated species leaching procedure by pressurized hot water extraction (PHWE). The operating parameters for PHWE including modifier concentration, extraction temperature, static time, extraction steps, pressure, mean particle size, diatomaceous earth (DE) mass/sample mass ratio and flush volume were studied using design of experiments (Plackett-Burman design PBD). Optimum condition implies a modifier concentration (acetic acid) of 150 mM and powdered hair samples fully mixed with diatomaceous earth (DE) as a dispersing agent at a DE mass/sample mass ratio of 5. The extraction has been carried out at 100°C and at an extraction pressure of 1500 psi for 5 min in four extraction step. Under optimised conditions, limits of quantification of 7.0, 6.3 and 50.3 ng g(-1) for total As, As(III) and As(V), respectively were achieved. Repeatability of the overall procedure (4.4, 7.2 and 2.1% for total As, As(III) and As(V), respectively) was achieved. The analysis of GBW-07601 (human hair) certified reference material was used for validation. The optimised method has been finally applied to several human scalp hair samples.

In vitro bioavailability of total selenium and selenium species from seafood.

In vitro bioavailability of total selenium and selenium species from different raw seafood has been assessed by using a simulated gastric and intestinal digestion/dialysis method. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to assess total selenium contents after a microwave assisted acid digestion, and also to quantify total selenium in the dialyzable and non-dialyzable fractions. Selenium speciation in the dialyzates was assessed by high performance liquid chromatography (HPLC) coupled with ICP-MS detection. Major Se species (selenium methionine and oxidized selenium methionine) from dialyzate were identified and characterized by HPLC coupled to mass spectrometry (HPLC-MS). Selenocystine was detected at low concentrations while Se-(Methyl)selenocysteine and inorganic selenium species (selenite and selenate) were not detected in the dialyzate. Low bioavailability percentages for total selenium (6.69±3.39 and 5.45±2.44% for fish and mollusk samples, respectively) were obtained. Similar bioavailability percentages was achieved for total selenium as a sum of selenium species (selenocystine plus oxidized selenium methionine and selenium methionine, mainly). HPLC-MS data confirmed SeMet oxidation during the in vitro procedure.

Analytical methodology for the determination of organochlorine pesticides in vegetation.

Due to the extensive use of organochlorine pesticides (OCPs) for agricultural purposes and their high persistence and low biodegradability, they have become an important group of contaminants. Detection and quantification of pesticide residues in food, particularly fruits and vegetables, is of growing concern for producers, consumers, and governments. The most widely used pretreatment for the extraction of pesticides in plants is based on solvent extraction liquid-solid extraction (LSE). LSE can be carried out using Soxhlet, shake-flask, homogenization, sonication, and, more recently, microwave-assisted extraction, pressurized liquid extraction, and supercritical fluid extraction. Furthermore, new analytical procedures using the extraction with sorbents, such as solid-phase microextraction, stir bar sorptive extraction, and matrix solid-phase dispersion, have also been used. On the other hand, a wide range of cleanup methods (liquid-liquid extraction, solid-phase extraction, gel permeation chromatography, and dispersive solid-phase extraction; and chromatographic techniques with electron capture detector and mass spectrometry detector; and HPLC with a ultraviolet detector are reported in the literature. This article reviews the applicability, advantages, and disadvantages of various sample preparation techniques (traditional and new techniques) for the analysis of OCPs in different plants and plant materials. It covers more than 15 years of published methods in which pesticide residues have been determined in a wide range of vegetation samples (fruits, horticultural samples, medicinal plants, tree leaves, etc.) by the use of chromatographic techniques after various sample preparation steps. A great number of applications in different plant material are provided. To the best of the authors' knowledge, previously published reviews have not covered as wide and exhaustive range of vegetation matrixes as presented here. A summary of pesticide levels cited in the literature is included.

Use of pressurized hot water extraction and high performance liquid chromatography-inductively coupled plasma-mass spectrometry for water soluble halides speciation in atmospheric particulate matter.

The feasibility of pressurized hot water extraction (PHWE) has been novelty investigated to speed up water soluble halide species (bromide, Br(-); bromate, BrO(3)(-); iodide, I(-) and iodate, IO(3)(-)) leaching from atmospheric particulate matter (PM(10) and PM(2.5)). Total bromine and iodine and total water soluble bromine and iodine have been assessed by inductively coupled plasma-mass spectrometry (ICP-MS). Water-soluble bromine and iodine species were also measured by ICP-MS after anion exchange high performance liquid chromatography (HPLC). Variables inherent to the pressurized hot water extraction process (temperature, modifier concentration, static time, pressure, number of cycles and dispersing agent mass) were fully studied. Results showed that the pressurized leaching procedure can be performed in 9 min (5 min for pre-heating, 2 min of static time, 1 min of purge time, and 1 min of end relief time). The use of diluted acetic acid as a modifier did not improve the target recoveries. Dispersing agent (diatomaceous earth) was not needed, which reduces the time for filling the cells. Water-soluble halides were reached under the following extraction conditions: extraction temperature of 100 °C, pressure of 1500 psi, static time of 2 min and 1 extraction cycle. Optimized HPLC conditions consisted of an isocratic elution with 175 mM ammonium nitrate plus 15% (v/v) methanol as mobile phase (optimum flow rate of at 1.5 mL min(-1)). Analytical performances, such as limits of detection and quantification, repeatability and analytical recoveries of the over-all procedure have been established. Results obtained show water soluble halides accounted for approximately 20.9±1.3 and 11.8±0.6% of the total bromine and total iodine, respectively. A 79 and 89% of bromine and iodine was non-water soluble, which may be organic non-water soluble species. Br(-) and IO(3)(-) were found to be the major species, and they accounted for 100% of the total water-soluble bromine and iodine.

Emerging pollutants in sewage, surface and drinking water in Galicia (NW Spain).

A monitoring programme was carried out on wastewater, surface and drinking water on the NW area of Spain during the four seasons of a year period (November 2007-September 2008). This study covered a series of emerging pollutants of different classes, including pharmaceuticals, neutral and acidic organophosphorus flame retardant/plasticizers (OPs), triclosan, phenoxy-herbicides, insect repellents and UV filters. From the total set of 53 compounds, 19 were found in raw wastewater with median concentrations higher than 0.1 µg L(-1). Among them, salicylic acid, ibuprofen and the UV filter benzophenone-4 (BP-4) were the most concentrated, exceeding the 1 µg L(-1) median value. Subsequently, 11 of these contaminants are not efficiently enough removed in the small WWTPs tested and their median concentrations in effluents still surpassed the 0.1 µg L(-1), so that they can spread through surface water. These chemicals are the pharmaceuticals naproxen, diclofenac and atenolol; the OPs tri(2-chloroethyl) phosphate (TCEP), tri(chloropropyl) phosphate (TCPP), tri-n-butyl phosphate (TnBP), diphenyl phosphate (DPhP) and diethylhexyl phosphate (DEHP); and the sulphonate UV filters BP-4 and 2-phenylbenzimidazole-5-sulphonic acid (PBSA). These OPs were then the dominant emerging pollutants occurring in surface and drinking water, where they are detected in the 20-200 ng L(-1) range. Pharmaceuticals and UV filters are typically below the 10 ng L(-1) level. Finally, herbicides were only detected in the last sampling campaign under the 100 ng L(-1) drinking water European Union limit.

Application of fast ultrasound water-bath assisted enzymatic hydrolysis--high performance liquid chromatography-inductively coupled plasma-mass spectrometry procedures for arsenic speciation in seafood materials.

Enzymatic hydrolysis of seafood materials for isolating arsenic species (As(III), As(V), DMA and AsB) has been successfully performed by assisting the procedure with ultrasound energy (35 kHz) supplied by an ultrasound water-bath. The use of pepsin, as a proteolytic enzyme, under optimized operating conditions (pH 3.0, temperature 40°C, enzyme to sample ratio of 0.3) led to an efficient assistance of the enzymatic process in a short period of time (from 4.0 to 30 min). The enzymatic extract was then subjected to a clean-up procedure based on ENVI-Carb™ solid phase extraction (SPE). An optimized anion exchange high performance liquid chromatography (HPLC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS) permitted the fast separation (less than 15 min) of six different arsenic species (arsenite, As(III); arsenate, As(V); dimethylarsinic acid, DMA; and arsenobetaine, AsB; as well as monomethylarsonic acid, MMA; and arsenocholine, AsC) in a single run. Relative standard deviations (n=11) of the over-all procedure were 7% for AsB and DMA, 11% for As(III) and 9% for MMA. HPLC-ICP-MS determinations were performed using aqueous calibrations covering arsenic concentrations of 0, 5, 10, 25, 100 and 200 µg L(-1) (expressed as arsenic) for As(III), As(V), MMA, DMA and AsC; and 0, 125, 250, 500, 750, 1000 and 2000 µg L(-1) (expressed as arsenic) for AsB. Germanium (5 µg L(-1)) was used as an internal standard. Analytical recoveries from the anion exchange column varied from 96 to 105% (enzymatic digests spiked with low target concentrations), from 97 to 104% (enzymatic digests spiked with intermediate target concentrations), and from 98 to 103% (enzymatic digests spiked with high target concentrations). The developed method was successfully applied to two certified reference materials (CRMs), DORM-2 and BCR 627, which offer certified AsB and DMA contents, and also to different seafood samples (mollusks, white fish and cold water fish). Good agreement between certified and found AsB concentrations was achieved when analyzing both CRMs; and also, between certified and found DMA concentrations in BCR 627. In addition, the sum of the different arsenic species concentrations found in most of the analyzed samples was statistically similar to the assessed total arsenic concentrations after a total sample matrix decomposition treatment.

A matrix solid-phase dispersion-gel permeation chromatography-programmed temperature vaporisation-GC-MS procedure for the analysis of polycyclic aromatic hydrocarbons in mussel samples.

A simultaneous matrix solid-phase dispersion extraction-gel permeation chromatography cleanup with programmed temperature vaporisation GC-MS determination is proposed for the analysis of parent and alkylated polycyclic aromatic hydrocarbons (PAHs) in mussel samples. The parameters affecting the extraction and elution efficiency were studied. Final conditions were: 0.5 g of mussel sample, 0.5 g diatomaceous earth as dispersant; and 4 g of Bio-Beads S-X3 for the gel permeation chromatography. Ethyl acetate/hexane (1:1, v/v) was selected for the elimination of the lipid fraction and the elution of PAHs. The detection and quantification limits achieved with this procedure were between 0.01 µg/kg and 0.67 µg/kg and 0.02 µg/kg and 1.93 µg/kg, respectively. The linearity of the method ranged between 5 µg/kg and 1000 µg/kg for most of the studied PAHs. The method was validated by the analysis of mussel tissue reference material (SRM 2977). The repeatability, intermediate precision and accuracy of the method obtained are in excellent agreement with the certified values. The proposed method is simple, precise and robust; no special instruments or costly equipment are required, and a reduction in the total time of analysis, sample handling and solvent consumption is achieved in comparison with classic procedures.

Simultaneous pressurized enzymatic hydrolysis extraction and clean up for arsenic speciation in seafood samples before high performance liquid chromatography-inductively coupled plasma-mass spectrometry determination.

The feasibility of pressurized conditions to assist enzymatic hydrolysis of seafood tissues for arsenic speciation was novelty studied. A simultaneous in situ (in cell) clean-up procedure was also optimized, which speeds up the whole sample treatment. Arsenic species (As(III), MMA, DMA, As(V), AsB and AsC) were released from dried seafood tissues using pepsin as a protease, and the arsenic species were separated/quantified by anion exchange high performance liquid chromatography (HPLC) coupled to inductively coupled plasma-mass spectrometry (ICP-MS). Variables inherent to the enzymatic activity (pH, temperature and ionic strength), the amount of enzyme (pepsin), and factors affecting pressurization (pressure, static time, number of cycles and amount of dispersing agent, C-18) were fully evaluated. Pressurized assisted enzymatic hydrolysis (PAEH) with pepsin can be finished after few minutes (two cycles of 2 min each one plus 3 min to reach the hydrolysis temperature of 50 °C). A total sample solubilisation is not achieved after the procedure, however it is efficient enough for breaking down certain bonds of bio-molecules and for releasing arsenic species. The developed method has been found to be precise (RSDs lower than 6% for As(III), DMA and As(V); and 3% for AsB) and sensitive (LOQs of 18.1, 36.2, 35.7, 28.6, 20.6 and 22.5 ng/g for As(III), MMA, DMA, As(V), AsB and AsC, respectively). The optimized methodology was successfully applied to different certified reference materials (DORM-2 and BCR 627) which offer certified AsB and DMA contents, and also to different seafood products (mollusks, white fishes and cold water fishes).

Sample preparation based on matrix solid-phase dispersion and solid-phase extraction cleanup for the determination of organochlorine pesticides in fish.

A method based on matrix solid-phase dispersion (MSPD) and SPE to determine 20 organochlorine pesticides (OCPs) in fish tissues (muscle and liver) was optimized in terms of the sorbents and elution solvents used for the analysis. The following analytical components were evaluated: ENVI-CarbTM and ENVI-18 as dispersing agents, Florisil and Florisil over alumina as cleanup adsorbents, and hexane and hexane-ethyl acetate (80 + 20) as elution solvents. The pesticides were determined by GC with electron capture detection. The best results were obtained with ENVI-Carb as a dispersing agent and an ENVI-Florisil co-column using 40 mL hexane-ethyl acetate (80 + 20) as the elution solvent. Analytical recoveries ranged between 75 and 130% except for beta-HCH in fish liver, and the RSD values were < 15% for most of the pesticides studied. Furthermore, sensitivity was sufficient (LOD of < 300 microg/kg) for all OCPs under study, in compliance with the tolerance limits of the U.S. Food and Drug Administration for OCPs in fish. The results were compared with those obtained by microwave-assisted extraction (MAE) and pressurized liquid extraction (PLE) in order to evaluate the performance of the MSPD procedure. The MPSD methodology was shown to be easy to use and fast, with a clear advantage relative to cost, because it does not need the expensive equipment required for MAE and PLE.

Investigating the chlorination of acidic pharmaceuticals and by-product formation aided by an experimental design methodology.

The degradation of seven acidic drugs and two metabolites during chlorination was investigated by liquid chromatography-mass spectrometry (LC-MS). A triple-quadrupole (QqQ) system was used to follow the time course of the pharmaceuticals and by-products, while a quadrupole time-of-flight (Q-TOF) system was also used for the identification of the by-products. Under strong chlorination conditions (10mg/L Cl(2), 24h), only four of the target compounds were significantly degraded: salicylic acid, naproxen, diclofenac and indomethacine. The degradation kinetics of these four compounds were investigated at different concentrations of chlorine, bromide and pH by means of a Box-Behnken experimental design. Depending on these factors, measured pseudo-first order half-lives were in the ranges: 23-573h for salicylic acid, 13-446min for naproxen, 5-328min for diclofenac and 0.4-13.4min for indomethacine. Also, it was observed that chlorine concentration was the overall most significant factor, followed by the bromide concentration (except for indomethacine), resulting in increased degradation kinetics as they are increased. The degradation path of salicylic acid, naproxen and diclofenac consisted of aromatic substitution of one or two hydrogens by chlorine and/or bromide. Moreover, for diclofenac, two other by-products corresponding to a decarboxylation/hydroxylation pathway from the monohalogenated products were also identified. On the other hand, indomethacine degradation did not lead to halogenation products but to oxidation ones. The investigation of these by-products in real samples by LC-MS/MS (QqQ) showed that the halogenated derivates of salicylic acid occurred in all the drinking water and wastewater samples analysed.

Temporal distribution, behaviour and reactivities of BTEX compounds in a suburban Atlantic area during a year.

The temporal distribution of BTEX compounds (benzene, toluene, ethylbenzene and xylene isomers) in ambient air was studied in a suburban Atlantic area in the northwest of Spain. These compounds mean serious risks for public and occupational health and for biological and physical environments. A total of 1200 samples were analysed during a year, and in most of the samples toluene was the most abundant VOC followed by benzene or m+p-xylene. The average concentrations were 1.62, 2.15, 0.60, 0.94 and 0.47 microg m(-3) for benzene, toluene, ethylbenzene, m+p-xylenes and o-xylene respectively, although they reached values as high as 50.53, 28.57, 21.33, 46.13 and 22.74 microg m(-3) for the compounds in the same order. An exhaustive study was carried out to establish how both emission sources and the climatic conditions affected the BTEX levels measured in the outskirts of a small city. Wind directions and speeds, daily and seasonal BTEX profiles, ratios among the concentrations measured in the sampling site, in the city centre and in the fuels commonly used by the cars in the city were studied. The pollution roses revealed the presence of diffuse BTEX sources affecting the sampling point, although all the compounds reached their highest levels when the wind blew from an industrial area in the SW of the city. The daily BTEX profiles were well-correlated with the traffic pattern in the accesses to the city and the seasonal profile showed that the highest concentrations were reported in summertime. The ratios T/B, m+p-X/B and o-X/B were 1.32, 0.58 and 0.29 respectively; these values were lower than the ones reported in previous studies carried out in the centre of the same city. This could be caused by the major distance from the sampling point to the city centre and by the changes in the fuels and in the kind of vehicles used in the city. The correlation coefficients among the TEX fraction were always higher than 0.72 but benzene only showed a good correlation with these compounds in winter. The correlations between BTEX concentrations and their contributions to the photochemistry in the sampling area were used in order to evaluate the distance from the road traffic source and to estimate the presence of fresh or old air masses in the sampling point. This study provides data which can be useful to establish the BTEX levels in suburban areas from the coastal Atlantic region and improves the knowledge of the BTEX presence in this kind of area.

Multi-residue analytical method for the determination of emerging pollutants in water by solid-phase extraction and liquid chromatography-tandem mass spectrometry.

This paper describes the development and validation of a method for the simultaneous determination of 53 multi-class emerging organic pollutants in water samples using solid-phase extraction (SPE) followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), using electrospray ionisation (ESI) in both positive and negative modes. Target compounds include acidic herbicides, UV filters, insect repellents, organophosphorous flame retardants, a bactericide, pharmaceuticals and metabolites. A single SPE consisting on the loading of 200-500 mL of sample adjusted to pH 7 on Oasis HLB 200mg cartridges and elution with methanol, permitted obtaining good recoveries: higher than 60% for tap, surface and wastewater in most cases. The 7 isotopically labelled internal standards effectively compensated losses during sample preparation and matrix effects at LC-MS/MS determination. The precision of the method, calculated as relative standard deviation (RSD) was below 15% for all compounds and all tested matrices. Detection limits (LODs) based on the confirmation, less intense, MRM (multiple reaction monitoring) transition and considering blanks varied between 0.3 and 30 ngL(-1). Finally, the developed method was applied to the determination of target analytes in various samples, including tap, surface and waste water. Among the tested emerging pollutants, 31 were found in wastewater in concentrations reaching up to 10 microgL(-1) in the case of ibuprofen. Also, 13 species were detected in tap water with concentrations up to 0.13 microgL(-1) for tri(chloropropyl) phosphate (TCPP).

Pressurized liquid extraction followed by high performance liquid chromatography coupled to hydride generation atomic fluorescence spectrometry for arsenic and selenium speciation in atmospheric particulate matter.

This paper describes the development of a chelating solvent-based pressurized liquid extraction (PLE) method for the simultaneous extraction of As and Se species (As(III), As(V), Se(IV) and Se(VI)) in atmospheric particulate matter (PM(10)). The extracted As and Se species were evaluated by high performance liquid chromatography coupled to hydride generation atomic fluorescence spectrometry (HPLC-HG-AFS). The feasibility of several pressurized chelating solvents was recently investigated to leach As and Se species from atmospheric particulate matter. The best results (high recoveries) were obtained when using EDTA. Experimental design approaches were used to achieve the best compromise conditions for the simultaneous extraction of As and Se species by EDTA-PLE. Analytical performances, such as limits of detection (in the range of 0.01-0.02 ng m(-3)), quantification (in the range of 0.02-0.07 ng m(-3)), and repeatability of the over-all procedure ( approximately 10%) were established. Finally, As and Se species were determined in several atmospheric particulate matter (PM(10)) samples collected in an urban area of A Coruña city (northwest coast of Spain) in 2006. In all the atmospheric particulate matter samples that were analysed, As(V) and Se(IV) (in the range of 0.17-0.60 ng m(-3)) were the major species found.

Pressurized liquid extraction and microwave-assisted extraction in the determination of organochlorine pesticides in fish muscle samples.

This paper describes a comparative study of 2 extraction methods, pressurized liquid extraction (PLE) and microwave-assisted extraction (MAE), for the determination of organochlorine pesticides (OCPs) in fish muscle samples. In both cases, samples were extracted with hexane-acetone (50 + 50), and the extracts were purified by solid-phase extraction using a carbon cartridge as the adsorbent. Pesticides were eluted with hexane-ethyl acetate (80 + 20) and determined by gas chromatography with electron-capture detection. Both methods demonstrated good linearity over the range studied (0.005-0.100 microg/mL). Detection limits ranged from 0.029 to 0.295 mg/kg for PLE and from 0.003 to 0.054 mg/kg for MAE. For most of the pesticides, analytical recoveries with both methods were between 80 and 120%, and the relative standard deviations were < 10%. The proposed methods were shown to be powerful techniques for the extraction of OCPs from fish muscle samples. Although good recovery rates were obtained with both extraction methods, MAE provided advantages with regard to sample handling, cost, analysis time, and solvent consumption. Acceptable validation parameters were obtained although MAE was shown to be more sensitive than PLE.

Determination of organic anions in atmospheric aerosol samples by capillary electrophoresis after reversed pre-electrophoresis.

This work presents the determination of low-molecular-mass (LMM) organic acids by CE after extraction with MeOH and preconcentration by evaporation. The interference arising from the simultaneous concentration of fast mobile anions (chloride, nitrate, and sulfate) at levels 200 times higher than those of LMM organic acids was reduced by the application of reversed pre-electrophoresis (RPE) as clean-up technique. This methodology allows for an effective elimination of high levels of fast mobile anions from the capillary before the separation has taken place, although analytes are also partially eliminated according to their electrophoretic velocities. In order to achieve an accurate quantification of organic anions, the use of a mathematical correction based on the linear relation between the analyte's effective volume removed during RPE and its mobility is proposed. Methods based on the use of one and two internal standards are discussed and evaluated. The proposed method is applied to the determination of organic acids in atmospheric particulate matter samples.

Multiclass determination of sunscreen chemicals in water samples by liquid chromatography-tandem mass spectrometry.

A novel analytical method based on solid-phase extraction (SPE) and liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) for the determination of UV sunscreen agents in the water environment is presented. After a thorough investigation of SPE and LC-MS/MS conditions, it permits the enrichment and determination of nine of these compounds in a single methodology, including three very polar sulfonates (e.g., 2-phenylbenzimidazole-5-sulfonic acid, PBSA) and six other less polar compounds (e.g., benzophenone-3, BP-3; octocrylene, OC,...). Other important matters of concern in the determination of UV filters at trace levels in water, i.e., adsorption on glassware and blank contamination problems, have also been discussed and minimized. This methodology affords detection limits between 7 and 46 ng L-1 and SPE recoveries in the range 63-102% from different real water matrixes, except for butylmethoxydibenzoylmethane (BM-DBM), which was not determinable in wastewater samples due to adsorption problems. The application of the method allowed reporting the levels of benzophenone-4 (BP-4) in environmental water samples for the first time, where it was identified as one of the most important in concentration among the UV filters studied, particularly in wastewater (237-1481 ng L-1).