Analytica Chimica Acta (v.524, #1-2)


Contents (vii-ix).

The recent trends in the development of environmental analysis are reviewed with emphasis on the progress of extraction techniques, of methods of analysis of pesticide residues in food, of the search for chemical and biological agents released into the environment, and of analytical instrumentation. A variety of new sorbents have been synthesized for the extraction and concentration of pollutants, including general purpose adsorbents (e.g., porous polystyrene/divinylbenzene resins) and polymers imprinted for specific compounds. New, faster, more selective and sensitive methods have been developed to improve analytical performance, e.g., synthetic fibers in the air pollution, stirbars coated with polymethylsiloxane. Bidimensional gas chromatography has brought a considerable leap in separation power and sensitivity. Finally the combination of open tubular columns and miniaturized quadrupole mass spectrometer allows the rapid identification of viral agents or a wide variety of chemicals.
Keywords: Instrumental analytical chemistry; Environment; Contaminants; Biological agents;

Use of mass spectrometry techniques for the characterization of metal bound to proteins (metallomics) in biological systems by J.L. Gómez-Ariza; T. Garcı́a-Barrera; F. Lorenzo; V. Bernal; M.J. Villegas; V. Oliveira (15-22).
The need to determine the individual chemical species (speciation), especially when they are known to have a differential action and behavior in relation to toxicity, mobility, or bioavailability, is discussed. The analytical approaches for small mass metal species characterization, as well as sample treatment and storage, is now well established on the basis of chromatographic-atomic detector combinations.The description of a new scenario centered on endogenous and exogenous metallic species in biological systems, bioactive macromolecules, such as proteins, DNA restriction fragments, phytochelatins, metallothioneins and others is fulfilled. Many of these systems are not well known at present and require a new generation of analytical tools that substitute the traditional atomic detectors based in the use of photons (atomic absorption spectrometry (AAS), flame photoionization detector (FPD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), atomic fluorescence spectroscopy(AFS)) by mass detectors (mass spectrometry (MS) and inductively coupled plasma-mass spectrometry (ICP-MS)) that characterize ions. The photonic analytical tool is now being substituted by the ionic paradigm. Many cases related to biological molecules involving proteins and multiprotein systems, in which metals frequently participate (metallomics) are described, and a generic metallomics analytical approach is proposed for the identification and quantification of metalloproteins, and other metallomacromolecules present in life systems, on the basis of three experimental focuses: (i) a separation technique—selectivity component; (ii) an element-high sensitivity detector—sensitivity component; and (iii) a molecule-specific detector, generally based on mass spectrometry—structural component. This multiplexed analytical approach brings together both elemental and molecular detectors for easy metalloproteins identification.Finally, the possibilities of the metallomics approach in the environmental, food and clinical fields are considered on the basis of a number of reported studies.
Keywords: Metallomics; Mass spectrometry; Inductively coupled plasma; Speciation;

As a result of the Prestige tanker sinkage on 19 November 2002, vast amounts of heavy fuel were dump from the shipwreck lying on the bottom to the surface of the NE Atlantic Ocean. The heavy metal contamination of the water column was studied from 4–8 December 2002 taking advantage of an opportunistic cruise onboard the R/V Atalante. Clean laboratory procedures were used in order to analyse 32 water samples and two heavy fuel samples (cargo tanker and surface seawater of the shipwreck area) by means of differential pulse anodic stripping voltametry and electrothermal atomic absorption spectrometry. Around 25 kg of Cd, 170 kg of Cu and 10 kg of Pb were released into the ocean water over seventy days of which 2% (Cd), 23% (Cu) and 71% (Pb) remain in the floating fuel patches on the sea surface. In the Prestige shipwreck area, where the seawater was free of oil patches, copper (2.8–8.5 nM) and lead (0.10–0.78 nM) contamination was only observed in the uppermost ocean layer, from 100 m depth for copper and the top ocean for lead. On the contrary, the cadmium levels (0.02–0.41 nM) observed were within typical or uncontaminated values.
Keywords: Cadmium; Copper; Lead; Seawater; Contamination; Oil spill; Heavy fuel; Prestige tanker;

Laser cleaning of Prestige tanker oil spill on coastal rocks controlled by spectrochemical analysis by M.P. Mateo; G. Nicolas; V. Piñon; J.C. Alvarez; A. Ramil; A. Yañez (27-32).
The potential of laser technology for controlled clean-up and analysis of Prestige tanker oil spill from coastal rocks is examined. Some of the massive cleaning methods cause more damage on the environment than they want to prevent. Laser treatment offers advantages with respect to these techniques such as the absence of additional residues and a minimal damage to the underlying substrate material. For these reasons, laser cleaning is presented as an alternative or complementary method in spills response available for minimizing their impact on the environment and human health.Test results of the yield of the laser cleaning process performed by a Nd:YAG laser emitting at two wavelengths are presented for various types of rocks polluted by the spill found on the north Galician coast. The laser cleaning process is controlled by the spectral analysis of the emission from the laser-produced plasma in order to avoid damage to the original rock surface. In order to provide complementary data, a morphological and compositional comparison of polluted and cleaned pieces has been performed by scanning electron microscopy and energy dispersive X-ray spectroscopy.
Keywords: Laser cleaning; Laser-induced plasma spectroscopy; Oil spill; Elemental analysis; On-line control;

Physical speciation of arsenic, mercury, lead, cadmium and nickel in inhalable atmospheric particles by F. Fernández Álvarez; M. Ternero Rodrı́guez; A.J. Fernández Espinosa; A. Gutiérrez Dabán (33-40).
Physical speciation of metals (size distribution) in airborne particles has been studied in 24 areas of Seville (Spain). Urban particles were collected with a high-volume sampling systems equipped with cascade impactor and PM10 inlets. Particle samples were analysed by acid digestion assisted by microwave heating using a HNO3:HClO4 (3:1,v/v) mixture. Arsenic was determined by hydride generation atomic absorption spectrometry (AAS), mercury by AAS with cold vapour atomisation and inductively coupled plasma atomic emission spectrometry was employed to determine lead, cadmium and nickel. Analyses of PM10 samples revealed that the highest mean concentration was obtained for Pb, 14.04 ng m−3. Values of 3.42 and 2.88 ng m−3 were obtained for As and Ni, respectively. The lowest concentrations were obtained for Cd, 0.49 ng m−3, and especially for Hg, 0.07 ng m−3. Their physical speciation in air concentrations (ng m−3) showed that the toxic elements As and Pb were accumulated in the fine particles of <0.6 μm diameter (PM0.6), as well as the metals Cd and Ni, with high percentages of 74.8, 69.0, 61.3 and 57.5, respectively. Hg constituted a lower percentage of 40.4%. The results in mass concentrations (mg kg−1) demonstrated that Pb and Cd contents were clearly greater in fine particles between 1.3 and 0.6 μm diameter than in PM0.6. The size interval where Hg contents were higher than in PM0.6 (4.9–0.6 μm) corresponded to a fine and also a coarse mode, meanwhile Ni presented similar percentages between all size ranges. As is mainly accumulated in PM0.6 in both air and mass concentrations, revealing that it constitute the element most hazardous in relation to its size distribution.
Keywords: Size distribution; Arsenic; Mercury; Airborne particles; PM10; Speciation; Microwave heating;

Application of validation data tests from an on-line volatile organic compound analyser to the detection of air pollution episodes in urban areas by Maria Carmen Gómez; Nieves Durana; Marino Navazo; Lucio Alonso; Jose Antonio Garcı́a; Juan Luis Ilardia (41-49).
This paper presents the routine and validation tests developed to evaluate 62 volatile organic compound (VOC) measurements (C2–C10), in ambient air from an on-line VOC analyser. These tests are based on experience obtained from application on hourly data sets obtained during April–October campaigns (1997–2001) at the Air Quality Monitoring Station sited at the School of Engineering, Bilbao (SEB) (Northern Spain). Every campaign yields 4000–4800 uninterrupted running hours, which amounts to about 1,200,000 valid data over the five intensive measuring campaigns. Quality control through data validation is critical to minimise the amount of faulty data reported, because erroneous individual data values give place to serious errors in data analysis results. These tests also allow the detection of unexpected concentration values of some pollutants. Air pollution episodes detected during data validation and meteorological influence analysis are presented. VOC data analysis together with complementary meteorological data may explain the main observed trends, especially for some of the VOCs. Acetylene and benzene are two clear cases: commonly used in the literature as vehicle emission tracers, the analysis show that, in many cases, they must be attributed to urban or industrial sources.
Keywords: Validation data test; Volatile organic compounds; Air quality; Ozone precursors; On-line VOC analysis;

Sampling and analysis of volatile organic pollutants emitted by an industrial stack by C. Domeño; Fca. Martı́nez-Garcı́a; L. Campo; C. Nerı́n (51-62).
The sampling of volatile organic compounds emitted by a process industry has been optimised and applied in realistic conditions. Two different fractions were obtained from the emission, one liquid from the condensation of the water vapour which contains the most polar compounds and another fraction of gas, which was trapped on an active carbon filter. Both fractions have been analysed by solid phase microextraction (SPME) with a polyacrylate fibre and then GC–MS. Once the composition of the industrial emission was known, two diffferent systems have been studied for reducing the air pollution. The first one involves a washing system with water and the second one combines the washing system with a chemical oxidation using NaClO–NaOH. A pilot plant has been installed connected to the industrial chimney for the study. Reduction factors of air pollution of 70 and 90%, respectively, have been found. The analytical results as well as the technological ones are shown and discussed.
Keywords: Volatile organic compounds (VOCs); Pilot plant; Oxidation; Sampling; Atmosphere;

Application of strategic sample composition to the screening of anti-inflammatory drugs in water samples using solid-phase microextraction by J. Carpinteiro; J.B. Quintana; E. Martı́nez; I. Rodrı́guez; A.M. Carro; R.A. Lorenzo; R. Cela (63-71).
The usefulness of the strategically designed sample composition (SSC) methodology for the screening of four anti-inflammatory drugs (ibuprofen, naproxen, tolfenamic acid and diclofenac) in water samples is demonstrated. Assuming that in screening campaigns only a limited number of the samples are contaminated with the analytes, the proposed approach allows the reliable identification of the contaminated specimens and the approximate estimation of their concentrations, with a 50% reduction in the total number of processed samples. To achieve this, a limited number of composite samples are built from the individual specimens. Automatic preparation of composite samples avoids human mistakes during this time-consuming and tedious operation, increasing the reliability of the predictions. In this work, a low-cost automatic device able to mix the individual specimens in the proportions indicated in the composition matrix is used. Moreover, the efficiency of evolutionary algorithms to predict the concentrations of the anti-inflammatory drugs in ultrapure and river water samples, artificially polluted in the laboratory and their robustness against large errors during the analysis of the composite samples, are evaluated.
Keywords: Strategic sample composition; Screening analysis; Anti-inflammatory drugs;

A simple method for the continuous field preconcentration of trace dissolved cadmium in seawater samples has been developed based on the minicolumn field sampling technique. For this purpose, minicolumns containing Chelite P (aminomethylphosphonic groups) were connected to a field flow preconcentration system (FFPS). Once in the laboratory, these minicolumns are sequentially inserted into a flow-injection system for on-line cadmium elution and detection by flame atomic absorption spectrometry. Factorial designs have been used to optimise the FFPS and the flow-injection elution process. Six experimental variables were optimised: sample pH, sample flow-rate, eluent concentration, eluent volume, eluent flow-rate and minicolumn diameter. The detection limit (3 F ) of the procedure was 2.7 ng l−1 for a sample volume of 300 ml. The precision (expressed as relative standard deviation) for 11 independent determinations was 0.5–9.4% for cadmium solutions of 10–300 ng l−1. Analysis of certified reference materials (SLEW-3 and NASS-5) showed good agreement with the certified values. This procedure has been successfully applied to the determination of cadmium in seawater samples from Galicia (Spain).
Keywords: Field sample preconcentration; Chelating minicolumns; Flow-injection; Cadmium; Seawater;

A novel expert multi-syringe flow-injection system has been developed. This system, which is able to choose for itself the best strategy to quantify the analyte, has been applied to the spectrophotometric determination, pre-concentration and speciation analysis of iron. The determination of the lowest iron concentrations benefits from the retention of the analyte on a chelating disk (iminodiacetic acid groups) which has been placed in a laboratory-made methyl methacrylate cylindrical device. A three-way solenoid commutation valve allows the deviation of the flow towards the chelating disk to follow the pre-concentration schemes when necessary. Ammonium thiocyanate was used as the chromogenic reagent for iron(III). Total iron can be determined by on-line oxidation of iron(II) to iron(III) with a hydrogen peroxide stream.A mass calibration was feasible in the wide range from 0.019 to 3 μg. The detection limit (3s b/S) was 19 ng. The repeatability (RSD), calculated from 11 replicates using 3 ml injections of a 0.5 mg l−1, was 2%. When pre-concentration was not required, two linear calibration graph between 0.1 and 20 mg l−1 and between 0.2 and 35 mg l−1 for the determination of iron(III) and total iron, respectively, were obtained. The proposed technique has been validated by replicate analysis (n=3) of a certified reference material of water with satisfactory results. The use of chelating disks offers several advantages over the conventional resin.
Keywords: Multi-syringe flow-injection analysis; Expert system; Chelating disk; Pre-concentration; Speciation analysis;

In-line membrane separation method for sulfide monitoring in wastewaters exploiting multisyringe flow injection analysis by Graciela de Armas; Laura Ferrer; Manuel Miró; José Manuel Estela; Vı́ctor Cerdà (89-96).
A fully automated multisyringe flow injection analysis (MSFIA) system coupled to gas-diffusion (GD) separation is proposed for the spectrophotometric determination of sulfide in urban wastewaters containing suspended solids. No preliminary batch sample treatment is required. The method carried out in a multicommutated system is based on analyte release as hydrogen sulfide from the donor channel of the GD module into a stagnant recipient solution composed of N,N-dimethyl-p-phenylene diamine (DMPD) and Fe(III). The methylene blue dye generated in-line via oxidative coupling is subsequently delivered downstream to a miniaturized flow-through light-emitting diode (LED)-based optical fiber plug-in spectrophotometer.The effect of various experimental variables on gas transfer across the membrane and concentration enhancement in the receiver solution via iterative flow reversals are discussed. Under the optimized chemical and hydrodynamic variables, the GD–MSFIA method features coefficients of variation better than 0.8% (n=10) at the 10 mg l−1 level, a linear working range of 0.5–20 mg l−1 sulfide, a 3σ blank-detection limit of 0.03 mg l−1 and an injection throughput of 13 h−1 for a sample volume of 700 μl and a forward flow mode. The analytical performance of the proposed GD–MSFIA system is also critically compared with that of in-line dialysis separation schemes using passive semi-permeable hydrophilic membranes. Accuracy was assessed by using the batch APHA–AWWA–WPFC standard method as an external reference.
Keywords: Sulfide; Multisyringe flow injection analysis; Gas-diffusion; Wastewater;

New trends involving the use of ultrasound energy for the extraction of humic substances from marine sediments by Antonio Moreda-Piñeiro; Adela Bermejo-Barrera; Pilar Bermejo-Barrera (97-107).
A new and fast method involving the use of ultrasound energy and moderate temperature has been developed to extract humic substances from marine sediments. The extractive process has been optimised by using a Plackett–Burman design as a multivariate optimisation approach. Temperature and the number of repeated extractions were the most significant variables (P=95%) affecting the extraction of both fulvic and humic acids from marine sediments. These two variables have optimum values of 65 °C and three repeated extractions. The combination of ultrasound energy and moderate temperature was also studied to optimise an acid treatment prior the sodium hydroxide extraction. Results from the Plackett–Burman design have revealed that all factors, except the ultrasound power for humic acids extraction, and the temperature and number of repeated acid treatments for fulvic acids extraction, were statistically significant (P=95%). Therefore, some of these factors were optimised using a central composite designs. The optimised acid treatment consisted in one sonication step at room temperature and ultrasound power at 17 kHz, with 10 ml of 6.0 M hydrochloric acid for 15 min. The developed method has been found to be precise (relative standard deviations of 8.7% for HA and 11.4% for FA, for 11 determinations) and its results were comparable (in terms of humic and fulvic acids concentrations and in terms of elemental (C, H and N) composition) to those obtained after applying methods based on mechanical stirring. The method was applied to marine sediments from the Rı́a de Arousa estuary.
Keywords: Humic substances; Marine sediments; UV-Vis spectrophotometry; Ultrasound energy;

The chemical speciation of dissolved Cu, Pb and Zn was studied in a ria coastal system applying differential pulse anodic stripping voltammetry using a hanging mercury dropping electrode. Cu and Pb were found to be strongly complexed with organic ligands in solution: inorganic Pb was not detected in the samples, whereas inorganic Cu only accounted for <3% of total dissolved metal. Organic complexation of Zn was weaker, ranging from 48 to 72% of total dissolved metal. Sediment resuspension experiments were carried out in order to study the desorption of organic ligands to the water column. Results from the sediment resuspension study showed a desorption of organic ligands (together with metals) presenting similar complexing abilities of those found in the water column. This has important implications from an ecotoxicological point of view, since the potential danger to the aquatic biota from significant concentrations of desorbed metals – which is critical when contaminated sediments are considered – is in part buffered by the in situ desorption of organic ligands.
Keywords: Chemical speciation; Trace metals; Differential pulse anodic stripping voltammetry; Sediment resuspension; Ria;

Study of cadmium, lead and tin distribution in surface marine sediment samples from Ria de Arousa (NW of Spain) by M.C. Barciela-Alonso; P. Pazos-Capeáns; M.E. Regueira-Miguens; A. Bermejo-Barrera; P. Bermejo-Barrera (115-120).
In this work a study of the Cd, Pb and Sn content in marine surface sediment from the Ria de Arousa has been realised. For this, 21 sediment samples were taken in triplicate, lyophilised and sieved, and the fraction <63 μm was taken for analysis. The samples were prepared in a form of slurries and analysed by electrothermal atomic absorption spectrometry. The concentration ranges obtained were 90–990 μg kg−1 Cd, 26.5–91.3 μg g−1 Pb and 5.0–20.8 μg g−1 Sn. The highest concentrations of these metals are in the inner part of the Ria, near to the port and urban nucleus such as Vilagarcı́a or Rianxo, and decrease toward the mouth of the Ria.
Keywords: Cadmium; Lead; Tin; Electrothermal atomic absorption spectrometry; Marine sediment samples; Slurries;

Chromium in marine sediment samples from the Rı́a de Arousa (Galicia, NW of Spain): analysis of the total content in slurries by ETAAS by P. Pazos-Capeáns; M.C. Barciela-Alonso; A. Bermejo-Barrera; P. Bermejo-Barrera (121-126).
The study attempts to measure the total chromium content in sediments of all the Rı́a de Arousa (Galicia, NW Spain). The method was developed by analysing slurries by electrothermal atomic absorption spectromety. The metal determination was carried out optimising the electrothermal programme and the concentration of magnesium nitrate as a chemical modifier.What was aimed to be achieved is a general explanation of the chromium content along the estuary because there could be a chromium sink in this marine environment. Results obtained were between 43.4±1.7 μg g−1 and 184.6±26.9 μg g−1 from the end of the Ulla river to the Atlantic Ocean, most of them higher than the background reference levels.
Keywords: Chromium; Marine sediments; Slurry; Electrothermal atomic absorption spectrometry; Rı́a de Arousa;

The present work demonstrates the application of fast scan linear sweep cathodic stripping voltammetry to the determination of acid-volatile sulphide (AVS) in salt marsh sediments. This approach combines very fast analysis with relatively high sensitivity without the need for additional reagents or derivatization procedures. The purge-and-trap AVS methodology was used. The sulphide content in the trapping NaOH solution was directly measured by voltammetry with a high scan rate (1000 mV s−1). The limit of detection (3σ) was 0.34 μmol L−1 for a deposition time of 5 s. Vertical distribution of AVS in sediments was determined in salt marsh sediments of a Portuguese coastal lagoon vegetated with H. portulacoides and correlated to the total dissolved mercury content in pore waters. At the depth of higher root biomass (around 20 cm), AVS concentrations (range 0.24–24.8 μmol g−1) were low in comparison to other depths, probably due to modifications in sediments that occur in the vicinity of the roots. The highest dissolved mercury concentrations (835 and 675 ng L−1), were found at the surface layer and at 20 cm depth, with an opposite trend from that of AVS. A possible explanation is that root activity reduced AVS concentrations at the depth of higher root biomass and resulted in elevated pore water concentrations of mercury. Concentrations of mercury in pore water from layers above and below the high root biomass were consistently lower (less than 152 ng L−1).
Keywords: Acid-volatile sulphide; Mercury; Cathodic stripping voltammetry; Salt marsh sediments;

Use of polyoxyethylene-6-lauryl ether and microwave-assisted extraction for the determination of chlorophenols in marine sediments by Cristina Mahugo Santana; Zoraida Sosa Ferrera; José J.Santana Rodrı́guez (133-139).
Microwave-assisted micellar extraction was optimised and applied to the extraction, prior to analysis by liquid chromatography with diode array spectrophotometric detection, of chlorophenols in marine sediment samples. This study was carried out using a non-ionic surfactant polyoxyethylene-6-lauryl ether as extractant. Parameters studied included surfactant concentration, pH of the solution, extraction time and power. Once the method was optimised, it was applied to different spiked marine sediments from coasts of the Canary Islands (Spain). The results obtained indicate that irradiation of 500 W for 2 min achieved the best extraction efficiency (100% recovery) and standard deviation values <10%. Detection limits were obtained in the range 1.2–12.7 μg g−1 for the chlorophenols studied. The proposed method provides a simple, fast and organic solvent-free procedure to analyse for chlorophenols in marine sediment samples.
Keywords: Chlorophenols; Micellar medium; Extraction methods; Microwave; Marine sediments; Liquid chromatography;

Relationships between heavy metals content and soil properties in minesoils by F.A. Vega; E.F. Covelo; M.L. Andrade; P. Marcet (141-150).
Mining can be important causes of environmental degradation. Opencast mines produce a large amount of waste because the ore is a small fraction of the total volume of the mined material. In mine spoils, the formed soils have severe physical, chemical and biological limitations. Minesoils usually have high heavy metal levels because wastes contain metallic minerals. High trace elements levels, mainly in available form, will impede the revegetation to stabilize the tailings.Twenty-five soils (Anthropic Regosols) were selected and characterized. Minesoils come from two mine tailings (Touro: copper mine and Meirama: lignite mine) located in Galicia (Spain). Total, DTPA-extractable and total dissolved contents of Cd, Cr, Cu, Ni, Pb and Zn were determined. Minesoils characteristics and heavy metal availability were related to establish the dependency among them.Total heavy metal dissolved and DTPA–extractable contents are low in all the soils except the Cu-dissolved content in soils from copper mine spoils. These soils have a total Cu content higher than the intervention limit of diverse reference guides.In Touro minesoils, Cr, Ni and Zn total contents come from the parent matter of these soils. The correlation established between the Cr, Ni, and Zn total content suggests its common origin through the soils parent matter. Heavy metal contents of Meirama minesoils, furthermore, come from the fertilizers, and animal manure. Iron and manganese oxides, humified organic matter, and clay minerals, like gibbsite, chlorite, smectite and goethite, are the soil components with greater effect in the decrease of heavy metal availability.
Keywords: Tailings; Soil characteristics; Heavy metals; Availability;

Abandoned mining sites contain residues from ore processing operations that are characterised by high concentrations of heavy metals. The form in which a metal exists strongly influences its mobility and, thus, the effects on the environment. Operational methods of speciation analysis, such as the use of sequential extraction procedures, are commonly applied.In this work, the modified three-stage sequential extraction procedure proposed by the BCR (now the Standards, Measurements and Testing Programme) was applied for the fractionation of Ni, Zn, Pb and Cd in mining wastes from old Pb–Zn mining areas located in the Val d’Aran (NE Spain) and Cartagena (SE Spain). Analyses of the extracts were performed by inductively coupled plasma atomic emission spectrometry and electrothermal atomic absorption spectrometry. The procedure was evaluated by using a certified reference material, BCR-701.The results of the partitioning study indicate that more easily mobilised forms (acid exchangeable) were predominant for Cd and Zn, particularly in the sample from Cartagena. In contrast, the largest amount of lead was associated with the iron and manganese oxide fractions.On the other hand, the applicability of lixiviation tests commonly used to evaluate the leaching of toxic species from landfill disposal (US-EPA Toxicity Characteristic Leaching Procedure and DIN 38414-S4) to mining wastes was also investigated and the obtained results compared with the information on metal mobility derivable from the application of the three-stage sequential extraction procedure.
Keywords: Mining wastes; Metal partitioning; Modified BCR sequential extraction; Toxicity characteristic leaching procedure; DIN 38414-S4; Inductively coupled plasma atomic emission spectrometry; Electrothermal atomic absorption spectrometry;

Sensitive determination of carbaryl in vegetal food and natural waters by flow-injection analysis based on the luminol chemiluminescence reaction by José Fernando Huertas-Pérez; Ana M. Garcı́a-Campaña; Laura Gámiz-Gracia; Antonio González-Casado; Monsalud del Olmo Iruela (161-166).
A sensitive and fast chemiluminescence (CL) flow-injection method has been described for the direct determination of carbaryl. The method is based on the enhancing effect of carbaryl on the CL emission generated by the oxidation of luminol with potassium permanganate in an alkaline medium. The optimisation of instrumental and chemical variables influencing the CL response of the method has been carried out by applying experimental design, using the proposed flow-injection manifold. Under the optimal conditions, the CL intensity was linear for a carbaryl concentration over the range of 5–100 ng ml−1 with a 3σ detection limit of 4.9 ng ml−1. The method has been successfully applied to the determination of carbaryl residues in water and cucumber samples.
Keywords: Carbaryl; Chemiluminescence; Luminol; Flow-injection analysis;

Amperometric screening of bacterial food contamination using a composite modified electrode by B. Palenzuela; B.M. Simonet; R.M. Garcı́a; A. Rı́os; M. Valcárcel (167-174).
An indirect determination of bacterial contamination based on catabolic metabolism of glucose is proposed. The determination of glucose was carried out by a flow injection (FI) system with amperometric detection using a wall-jet flow cell. A new composite PVC–graphite electrode modified with Cu2O was developed to improve the analytical features of glucose determination. A 25 mM saline buffer sodium phosphate in 0.2 M NaOH was used as the carrier for glucose. After optimising the sensing electrode in terms of composite electrode formulation, hydroxide ion concentration and operating potential, the detection limit for glucose was 1.1×10−3  M for 100 μl injections. The proposed method allows the successful determination of pollution bacteria in food samples in 3 h as compared to the 24–48 h required using the plate count method. The detection limit for bacteria in the samples was 2×102  cfu ml−1 and the reproducibility was in the range 2.6–3.8%. The efficiency of this method was tested for eight types of bacteria and five kinds of food. A comprehensive study of 30 spiked samples and 30 blank samples provided 4% of false positives and 0% of false negatives showing the applicability of the proposed method for sample screening.
Keywords: Bacteria analysis; Food samples; Sample screening; Amperometric detection; d-Glucose;

A fast and accurate method for the determination of zearalenone (ZON) and α-zearalenol (α-ZOL) in ground wheat samples has been optimised using accelerated solvent extraction (ASE) and liquid chromatography (LC) with fluorescence detection. The effects of the experimentally controllable ASE parameters (solvent composition, temperature, pressure, number of extraction cycles and sample cell size) on the extraction efficiencies of the target analytes have been investigated using wheat samples fortified at the ng g−1 level. The optimum extraction conditions were obtained using a 11 mL ASE cell, methanol/acetonitrile (50:50 v/v) as the extraction solvent, 1500 psi, 50 °C, a 5 min static time and a 60% flush volume. The extracted samples were analysed using LC with fluorescence detection (λ exc=271 and λ em=452 nm). The stationary phase was a polar endcapped C18 column and acetonitrile/methanol/water 10/55/35 (v/v/v, 15 mM ammonium acetate) at a flow rate of 1.0 mL min−1 was used as the mobile phase. The injection volume was set at 8 μL. Mean recovery rates of 98.4% for α-ZOL (RSD<4.6%) and 96% for ZON (RSD<4.0%) have been obtained for wheat samples fortified with 50–200 ng g−1 of ZON and α-ZOL. The optimised procedure has also been applied to the determination of ZON and α-ZOL in corn, rye, barley, rice and swine feed. Excellent extraction recoveries were achieved for both analytes in all the samples tested, except for α-ZOL in rice. The developed ASE-LC method has been validated using fortified wheat samples and the results have been compared with those provided by the official AOAC-LC method.
Keywords: Zearalenone; α-Zearalenol; Accelerated solvent extraction; Mycotoxin; Food analysis;

Modified atmosphere packaging and temperature effect on potato crisps oxidation during storage by A. Sanches Silva; J. López Hernández; P. Paseiro Losada (185-189).
Evaluation of lipid oxidation in potato crisps has been studied extensively. Most times, the study was done on potato crisps recently prepared by deep-fat frying, comparing different frying oils. In the present work, an extraction method that involves extraction and derivatization of free fatty acids to fatty acids methyl esters in a single step followed by gas chromatography is used. On the one hand, four potato crisps brands, fried in different oils, were stored at room temperature and at 40 °C, in the dark, to evaluate the effect of temperature on the fatty acids. On the other hand, a single kind of potato crisps (fried in olive oil), was stored at room temperature, in darkness, under different atmospheres: air, vacuum, oxygen scavenger, and nitrogen. The most effective conditions in order to avoid or at least delay lipid oxidation were storage at room temperature with an oxygen scavenger.
Keywords: One-step extraction methylation extraction; Modified atmosphere packaging; Temperature; Lipid oxidation; Potato crisps;

Study of the effect of light on fatty acids of potato crisps using a gas chromatographic method by A. Sanches-Silva; J. López-Hernández; P. Paseiro-Losada; J. Simal-Lozano (191-200).
A storage study was carried out to evaluate the behavior of fatty acids of potato crisps. Samples were stored in darkness and under natural light. A one step extraction–methylation method followed by gas chromatographic determination was used to analyze and compare profiles (% area) and contents (g/100 g sample). Quantification was carried out using nonadecanoic acid as internal standard. The profile of potato crisps stored in darkness did not show considerable variation, while that of crisps exposed to natural light decreased significantly. Regarding the FAME content, there was a decrease under both conditions, which was more evident in crisps stored under light. Because it greatly contributes to the development of lipid oxidation, light should be avoided during potato crisps storage.
Keywords: Fatty acids; Gas chromatography; Light; Potato crisps;

A method for the determination of wine carbonyl compounds with 5–8 carbon atoms including 3-methylbutanal, E-2-hexenal, E-2-heptenal, E-2-octenal and phenylacetaldehyde has been developed. Aldehydes are retained in a solid phase extraction cartridge and derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine takes place in the same cartridge at room temperature (25 °C) in 15 min. The corresponding oximes are further eluted and determined by gas chromatography–mass spectrometry. Isolation, derivatization and elution conditions were examined. Recoveries from red wines are all >94%, and are consistent from wine to wine. For white wines, recoveries for E-2-heptenal, E-2-octenal and phenylacetaldehyde are 80–85%, but are consistent from wine to wine. Precision (measured as relative standard deviation) is <7% in all cases. Method detection limits ranged from 0.12 to 0.70 μg L−1 and linearity holds at least up to 60 μg L−1 with r 2 in the range 0.9957–0.9997. The method has been applied to the determination of these components in several wine samples. Results show that phenylacetaldehyde, E-2-octenal and 3-methylbutanal can be found at concentrations above their corresponding odor thresholds in normal wines.
Keywords: Aldehydes; 3-Methylbutanal; E-2-hexenal; E-2-heptenal; E-2-octenal; Phenylacetaldehyde; Wine; Aroma; Derivatization; Solid phase extraction; Gas chromatography–mass spectrometry;

Migration order of wine anthocyanins in capillary zone electrophoresis by David Calvo; Rubén Sáenz-López; Purificación Fernández-Zurbano; Marı́a Teresa Tena (207-213).
Capillary zone electrophoresis (CZE) is an advantageous alternative to liquid chromatography (LC) in the analysis of wine anthocyanins in terms of separation efficiency, analysis time and reagent consumption. Thirteen wine anthocyanins of a Tannat wine, including acylated and non-acylated anthocyanin monoglucosides, pyranoanthocyanins and flavanol derivates, were separated using a 46 cm × 75 μm (i.d.) fused-silica capillary and a 50 mM sodium tetraborate buffer of pH 8.4 with 15% (v/v) methanol as modifier. Some of the pigments were isolated by LC fractionation and concentrated by lyophilisation. The reconstituted fractions were analysed by CZE in order to identify the compounds in the electrophoregram and to determine their migration times. The migration order found for the wine anthocyanins is discussed taking into account the molecular charge and mass, and the possibility of complex formation with tetraborate molecules.
Keywords: Anthocyanins; Wine; Capillary zone electrophoresis;

Evolution of metal and polyphenol content over a 1-year period of vinification: sample fractionation and correlation between metals and anthocyanins by I. Esparza; I. Salinas; I. Caballero; C. Santamaría; I. Calvo; J.M. García-Mina; J.M. Fernández (215-224).
Tempranillo grape variety (Vitis vinifera) samples obtained from a 0–345-day period of vinification were analysed. Fe, Cu, Zn and Mn were quantified as well as polyphenols and anthocyanins. A good correlation has been found for both Fe and Cu with total polyphenols and anthocyanins. A selected sample was fractionated through an open column, allowing the individual correlation of both Zn and Cu with cyanidin-3-glucoside to be established.
Keywords: Anthocyanins; Polyphenols; Heavy metals; Vinification; Fractionation; Wine colour;

Classification of apple beverages using artificial neural networks with previous variable selection by M. Gestal; M.P. Gómez-Carracedo; J.M. Andrade; J. Dorado; E. Fernández; D. Prada; A. Pazos (225-234).
Parallel to increased consumption of fruit juices over the last years (thanks to their unrivalled nutritional benefits), fraudulent fruit juices can be found sometimes on the food supply chain. Infrared spectrometry (IR) is a fast and convenient technique to perform screening analyses to assess the quantity of pure juice in commercial beverages. The IR information has some “fuzzy” characteristics (random noise, unclear chemical assignment, etc.) and, therefore, advanced computation techniques (e.g., artificial neural networks (ANNs)) are needed to develop ad-hoc classification models. Dissapointingly, the large number of variables derived from IR spectrometry makes ANNs to take too much time to train. This work studies two different genetic algorithms (GAs) intended to select a small number of wave numbers which are to be used to develop classification models, “pruned search” and “fixed search” (in both cases a steady state GA algorithm with uniform crossover where one of the parents is chosen following the “roulette-wheel” approach, was used). In order to compare results of different assays, the number of selected variables was fixed using an external criterion (a parametric model based on Procrustes rotation). Usefulness of the GAs is evaluated by developing PLS, potential functions, SIMCA and ANNs models to classify apple juice-based commercial beverages.
Keywords: Artificial neural networks; Genetic algorithms; Variable selection; Procrustes rotation; Juice authentication; Infrared spectroscopy;

Determination of a N-methylcarbamate pesticide in environmental samples based on the application of photodecomposition and peroxyoxalate chemiluminescent detection by Jorge Juan Soto-Chinchilla; Ana M. Garcı́a-Campaña; Laura Gámiz-Gracia; Luis Cuadros-Rodrı́guez; José Luis Martı́nez Vidal (235-240).
A new sensitive analytical procedure for the determination of a N-methylcarbamate pesticide (carbaryl) is presented, based on the participation of a fluorescent derivative of the pesticide in the peroxyoxalate chemiluminescent (PO–CL) system using imidazole as a catalyst. The chemiluminescent emission is detected in a flow injection (FI) manifold, employing sodium dodecyl sulfate micellar medium as carrier, which avoids the rapid degradation of a PO in water. The formation of the fluorescent derivative implies the previous decomposition of carbaryl to methylamine (MA) by UV irradiation and subsequent derivatisation with o-phthalaldehyde (OPA), carried out off-line. Photodecomposition allows a rapid degradation of carbaryl in MA, which implies some advantages in relation to the traditional hydrolysis in alkaline medium, such shorter analysis time and easier application. The optimisation of the operational and chemical variables affecting the CL response was carried out by using experimental design strategies. The method has been successfully applied to different natural waters and vegetal sample, obtaining satisfactory recoveries in both cases, with detection limits in compliance with the maximum limit of residues (MLR) permitted.
Keywords: Carbaryl; Chemiluminescence; Flow injection analysis; Peroxyoxalate system;

Evidence of 2,7/2,8-dibenzodichloro-p-dioxin as a photodegradation product of triclosan in water and wastewater samples by Milagros Mezcua; M.José Gómez; Imma Ferrer; Ana Aguera; M.Dolores Hernando; Amadeo R. Fernández-Alba (241-247).
A photodegradation study of triclosan, a commonly used antimicrobial agent, was carried out in order to investigate the formation of dibenzodichlorodioxin as a by-product of photodegradation in various environmental matrices and under different conditions. Deionized water and wastewater samples, spiked at 8 μg/mL with triclosan, were irradiated with natural sunlight. Aliquots of the spiked water samples were taken at different times of irradiation and compounds were isolated from the water samples by solid-phase extraction. Separation and detection of the compounds and degradation products was accomplished by gas chromatography–mass spectrometry. A major photolysis degradation product of triclosan, 2,7/2,8-dibenzodichloro-p-dioxin, was identified in wastewater samples. The photolysis experiment showed the simultaneous disappearance of triclosan and the appearance of the dioxin dependent on the pH and the organic matter content. Furthermore, a pilot survey monitoring for influent and effluent waters from a wastewater treatment plant was carried out. The presence of triclosan in all wastewater samples analyzed was revealed and dioxin was found in 80% of the cases, in influents and effluents, thus indicating its input and persistence through the wastewater treatment process. This represents a major finding since dioxins are more toxic than triclosan. Moreover, the presence of such compounds in wastewaters revealed the immediate need to improve the “classical” water treatment techniques, as well as considering limitation in water re-use.
Keywords: Triclosan; 2,7/2,8-Dibenzodichloro-p-dioxin; Photodegradation; GC–MS; Water; Waste water;

A procedure for the determination of nine phenoxy acid herbicides in water samples using gas chromatography in combination with mass spectrometric detection is presented. Analytes were concentrated from water samples using a solid-phase extraction (SPE) polymeric sorbent, functionalised with N-vinylpyrrolidone. Compounds were eluted from the SPE cartridge using ethyl acetate and silylated with N-methyl-N-(tert-butyldimethylsilyl)trifluoracetamide (MTBSTFA). The influence of several factors on the yield of the silylation reaction and on the stability of the obtained compounds is described. Under optimal conditions derivatisation was performed at room temperature, for 5 min, using 100 μl of MTBSTFA. The obtained derivatives were stable for at least 5 days after preparation. Using a sample intake of 1000 ml, the quantification limits of the proposed method ranged from 1–4 to 4–12 ng l−1 for surface and sewage water, respectively. Recoveries between 80 and 120% were obtained depending on each particular compound and the kind of water sample considered.
Keywords: Phenoxy acid herbicides; Silylation; Gas chromatography–mass spectrometry; Solid-phase extraction;

Determination of cyromazine in pesticide commercial formulations by vibrational spectrometric procedures by Sergio Armenta; Guillermo Quintás; Salvador Garrigues; Miguel de la Guardia (257-264).
Two vibrational spectrometry-based methodologies were developed for Cyromazine determination in solid pesticide formulations: a Fourier transform infrared (FTIR) procedure, based on the extraction of Cyromazine by CH3OH and direct determination in the extracts by peak height measurement at 1622 cm−1 corrected using a baseline defined at 1900 cm−1, and a FT-Raman determination, made directly on the powdered solid products using standard chromatographic glass vials as sample cells and measuring the Raman intensity between 633 and 623 cm−1 for a baseline established between 663 and 601 cm−1. The sensitivity obtained was 0.01631 absorbance g−1  mg for FTIR determination and 2.23 area values g−1  g for FT-Raman. A repeatability of 0.2 and 0.4% as relative standard deviation (R.S.D.) and a limit of detection of 0.2 and 0.8% (w/w) were obtained for FTIR and FT-Raman determination, respectively.FTIR determination provides a sampling frequency of 60 h−1, higher than the FT-Raman and LC ones, which were 25 and 6 h−1, respectively. On the contrary FT-Raman reduces to the minimum the reagents consumption and waste generation, also avoiding sample handling and contact of the operator with the pesticide. Results obtained by both developed procedures were statistically comparable with those found by a reference liquid chromatography procedure. It can be concluded that the proposed methods are appropriate for quality control in pesticide commercial formulations.
Keywords: Cyromazine; Pesticide formulations; FTIR; FT-Raman; Solid samples;

Micellar extraction of organophosphorus pesticides and their determination by liquid chromatography by C. Padrón Sanz; R. Halko; Z. Sosa Ferrera; J.J. Santana Rodrı́guez (265-270).
Methodology to extract and determine eight organophosphorus pesticides (Chlorpyrifos, Diazinon, Dimethoate, Ethoprophos, Malathion, Methidathion, Parathion methyl and Paration ethyl), that are in current use in agriculture and animal husbandry, was optimised. The surfactants used as extractants, polyoxyethylene 10 lauryl ether (POLE) and oligoethylene glycol monoalkyl ether (Genapol X-080), belong to the non-ionic surfactants family, which allow the extraction and preconcentration of the analytes under study in a single step. This procedure, known as cloud-point extraction, offers a series of advantages over the traditional methodologies applied to the extraction of organic compounds such as pesticides. The parameters and variables that affect the extraction of these substances using both surfactants were established followed by liquid chromatographic determination. The optimised method, once validated using the standard Pesticide Mix 1 (EPA Method 914), was successfully applied to spiked water samples from Gran Canaria Island.
Keywords: Cloud-point extraction; Liquid chromatography; Organophosphorus pesticides; Groundwater; Depurated waste water;

A comparative study on several extraction/clean-up procedures to determine total amitraz residues in beeswax is presented. The procedures are tested on samples spiked with amitraz, N-(2,4-dimethylphenyl)-N′-methylformamidine (DPMF) and 2,4-dimethylaniline (DMA) at two concentration levels. The extraction with methanol followed by a partitioning with n-hexane seems to be the most adequate procedure in terms of recovery (about 80%) and precision (R.S.D. lower than 15%). The analytes in the extracts are determined by GC/ECD after their hydrolysis to DMA and subsequent formation of the heptafluoro-N-(2,4-dimethylbenzene)-butanamide.
Keywords: Gas chromatography; Extraction and clean-up procedures; Total amitraz residues; Beeswax;

A fast, simple method that allows the direct screening of sediment samples for polycyclic aromatic hydrocarbons (PAHs) by the use of a flow manifold coupled on-line to a fluorimetric detector is reported. The method avoids the need to use expensive instruments such as a liquid chromatograph equipped with a scanning fluorescence detector. The proposed experimental set-up allows PAHs in supercritical fluid extracts to be selectively retained on a column packed with polytetrafluoroethylene (PTFE) accommodated in the loop of a high-pressure injection valve. Retained PAHs are subsequently eluted with acetonitrile and directly driven to the fluorimetric detector. Samples testing positive for PAHs are subjected to liquid chromatography in order to separate, identify, and quantify the analytes. This allows anthracene, pyrene, benzo(a)anthracene, 1,2-benzodiphenylene sulfide and benzo(k)fluoranthene to be quantified. The proposed method provides analytical information of two types, namely: (a) a yes/no overall response and (b) confirmation of species in the samples testing positive for PAHs. The precision of the screening method for a 0.100 μg ml−1 mixture of PAHs, expressed as relative standard deviation (R.S.D.), was 3.9% (n=11). The determination of five PAHs in spiked sediment provided R.S.D. values less than 5.5% in all instances. PAH recoveries ranged from 89 to 110%. The method was validated by application to spiked sediment samples.
Keywords: Supercritical fluid extraction (SFE); Polycyclic aromatic hydrocarbons (PAHs); Screening method;

Optimization of a sampling method to determine polycyclic aromatic hydrocarbons in smoke from incomplete biomass combustion by Francisco J. Conde; Juan H. Ayala; Ana M. Afonso; Venerando González (287-294).
A method of sampling for the determination of polycyclic aromatic hydrocarbons (PAHs) and their methyl derivatives in smoke samples from the incomplete combustion of different types of biomass is developed. The smoke is used for the smoking of foods, following an artisan procedure used in some places in the Canary Islands. By means of a factorial design, the variables with more influence in the sampling have been optimized: sampling temperature, sampling flow and composition of the adsorbent. The used sampling system is formed by a quartz fibre filter and an adsorbent constituted by PUF/XAD-2/PUF. For the treatment of the sample, the procedure described in UNE-77250 regulation is used, and the determination is carried out by gas chromatography–mass spectrometry. The results obtained in the present work show the necessity to analyse the filter and the adsorbent together, and that the retention efficiencies, when the temperature of the smoke is not too high, are usually >70%. Also, it is shown that for a correct interpretation of the results obtained when establishing the content of PAHs and their methyl derivatives in the smoke samples, it is necessary to take into consideration the temperature of the smoke at the point of sampling.
Keywords: Smoked food; Smoke; Factorial design; Polycyclic aromatic hydrocarbons; Gas chromatography/mass spectrometry;

Characterization of sludge from waste water treatment plants which are destined to be spread on agricultural lands, is a priority need. Inorganic pollutants are regularly controlled but organic pollutants have received little attention up to now. In this paper, we have developed an analytical procedure using microwave-assisted extraction prior to liquid chromatography coupled with diode array (LC-DAD) or fluorescence (LC-FL) detectors for the determination of polycyclic aromatic hydrocarbons (PAHs) in sewage sludge. The main factors affecting the extraction efficiency (microwave power, irradiation time and extractant volume) were optimized. Clean-up of sewage sludge extracts was not found to be necessary. For adequate fluorescence detection of PAHs a temporal program of excitation and emission wavelengths was used. The optimized method was applied to the extraction of PAHs from various sludges from a waste water treatment plant (Jerez de la Frontera, Cadiz, Spain). The limits of detection were between 4 ng g−1 sewage sludge for benzo[b]fluoranthene and 12 ng g−1 sewage sludge for pyrene using LC-FL. When LC-DAD is used the limits of detection were between 13 ng g−1 for indeno[1,2,3-cd]pyrene and 62 ng g−1 for naphthalene. The relative standard deviations were found to be <10%. The validation of the proposed method was carried out by application to analysis for PAHs in a certified reference material (CRM) 088 dried sewage sludge of the Community Bureau of Reference (BCR). The recoveries were between 69% for benzo[k]fluoranthene and 110% for pyrene using LC-FL and between 52% for indeno[1,2,3-cd]pyrene and 104% for benzo[a]pyrene using LC-DAD of the certified values. These results are in a very good agreement with those given in the literature.
Keywords: Microwave-assisted extraction; Sewage sludge; Polycyclic aromatic hydrocarbons;

Selenium species present in yeast samples were extracted using pressurised liquid extraction (PLE). Several experimental variables (dispersant agent, time, number of cycles, temperature, pressure and solvent) were evaluated for the extraction of selenocysteine, selenomethionine, selenoethionine, selenite, (Se(IV)) and selenate (Se(VI)) from spiked yeast. Only time, temperature and solvent had an influence on the recoveries. Subsequently, a central composite design was used to investigate the dependence of these operating variables on the recoveries from both spiked and native yeast. The results indicated that experimental conditions were different for spiked and native yeast. The optimum extraction conditions for the native yeast were 11 ml PLE cell, celatom as dispersant agent, 1:1 (v:v) H2O:MeOH, 1600 psi, 160 °C, 10 min static time, and 75 vol.% flush. The results obtained by PLE were compared to those obtained by mechanical agitation, sonication and Soxhlet extraction. The extracted selenium compounds were analysed by liquid chromatography (LC)–hydride generation (HG)–atomic fluorescence spectrometry (AFS).
Keywords: Selenium compounds; Yeast; Pressurised liquid extraction; Experimental design;

Selenium species present in water-soluble fractions of proteins of lyophilised biological samples, such as fish (tuna and trout), shellfish (krill, oyster and mussel), vegetal tissues (white clover and wheat flour) and selenized yeast were evaluated. The water-soluble fractions with and without 4% (w/v) sodium dodecyl sulphate were analysed by size exclusion chromatography coupled to both inductively coupled plasma–mass spectrometry (SEC–ICP–MS) and UV spectrophotometers. Two different columns with effective separation ranges between 300 and 1 kDa (Biosep-SEC-2000) and 7 and 0.1 kDa (Superdex Peptide HR 10/30) were used, with 5 mM sodium phosphate at pH 7.2 (0.8 ml min−1) and 5 mM sodium phosphate with 60 mM NaCl at pH 7.5 (0.6 ml min−1) as mobile phases, respectively.The enzymatic digests of both the water-soluble fractions and the non-soluble residues were analysed by cation exchange chromatography–ICP–MS, using a Hamilton PRP-X200 column and 4 mM pyridine (1 ml min−1) at pH 2.8 and 4.7 as mobile phases.The presence of high molecular weight selenoproteins (150–50 kDa) in the samples studied, except for fish and white clover with proteins <30 kDa, was demonstrated and low molecular weight (<5 kDa) compounds were also found.Selenomethionine species (SeMet) within the range of 0.2–600 μg g−1 was quantified in the selected tissues, although selenocystine (SeCys2) was identified only in vegetal samples (0.1–0.7 μg g−1). Trimethylselenonium ion was quantified (0.1–0.3 μg g−1) in oyster, mussel, trout and white clover tissues. Inorganic selenium as selenite was found in the selenized yeast, krill, and white clover samples (0.2–3 μg g−1), while selenate was found to be present only in yeast tissues (8 μg g−1).
Keywords: Selenium; Speciation; Selenium-containing proteins; Liquid chromatography–inductively coupled plasma–mass spectrometry; Mass spectrometry;

Evaluation of two atomisation modes for direct determination of molybdenum in complex matrices by ultrasonic slurry sampling–electrothermal atomic absorption spectrometry by M. Felipe-Sotelo; A. Carlosena; E. Fernández-Fernández; S. Muniategui; P. López-Mahı́a; D. Prada (329-337).
Tube wall (TWA) and L’vov platform (LPA) atomisations were compared for the direct determination of molybdenum (Mo) in coal fly ash by slurry sampling–electrothermal atomic absorption spectrometry (ETAAS). For both atomisation modes eight chemical modifiers were tested, namely HNO3, Pd(NO3)2, Mg(NO3)2, Pd + Mg(NO3)2, reduced Pd, BaF2, Ir and HF. The interfering effects of major and minor concomitants of samples on Mo signals and memory effects were also evaluated. BaF2 and Pd(NO3)2 + Mg(NO3)2 mixture were selected for TWA and LPA, respectively. Standard addition calibration is needed in both cases. The best peak performance, memory effect reduction, within-run precision (6% versus 9% R.S.D.), and sensitivity (m o = 7.5 pg versus 15.2 pg) were achieved with TWA compared to LPA. Both atomisation modes gave good analytical recoveries (94–102%), but the analysis of a certified coal fly ash (NIST SRM 1633a) only was accurate using TWA. Additionally, the urban dust NIST SRM 1629a was analysed.
Keywords: Mo; Chemical modifiers; Slurry sampling–ETAAS; Coal fly ash;

Development of ionoselective electrochemical sensors by using the sol–gel process by J.A. Rodrı́guez Gutiérrez; M.D. Petit Domı́nguez; J.M. Pinilla Macı́as (339-346).
Electrochemical sensors based on electrodes modified with entrapped ion-exchange polymers using the doping sol–gel method has been developed. Poly(dimethyldiallylammonium chloride) (PDMDAAC) or poly(vinylsulfonic acid, sodium salt) (PVSA) has been used as anionic and cationic ion exchangers respectively. Spectroscopic grade graphite electrodes were modified with the polymer–sol–gel solution obtained, and characterised by square wave voltammetry (SWV) using Fe(CN)6 4− for the anionic exchange polymer and methyl viologen dichloride (MVDC) for the cationic exchange polymer. The process take place in two independent stages, providing the most adequate medium (pH, ionic strength) in the selective preconcentration and in the measurement steps; increasing in this way selectivity and sensibility of the developed sensors. Modified electrodes give detection limits two and three orders of magnitude (for the cationic and anionic polymer respectively) lower than the analogous graphite electrodes. Furthermore, the polymer–sol–gel electrode surfaces were easily renewed by reversing the ion-exchange reaction. Shrinking/swelling effects of films deposited in the electrode surfaces as well as leaching out of polymers from the sol–gel were not observed. Good reproducibility of the analytical procedures developed were also obtained.
Keywords: Electrochemical sensors; Sol–gel; Ion-exchange; Square wave voltammetry;

Ion-selective carbon paste electrode based on tetraethyl thiuram disulfide for copper(II) and mercury(II) by M.Jesús Gismera; David Hueso; Jesús R. Procopio; M.Teresa Sevilla (347-353).
Tetraethyl thiuram disulfide was chosen as a chemical modifier in a carbon paste electrode for the potentiometric determination of copper(II) and mercury(II) ions. The electrode has wide linear response ranges and rapid response times. The pH influence on the potentiometric response is studied. Selectivity coefficients towards different cationic species are tabulated. The limits of detection are 10−7.4 and 10−7.6  M for copper (II) and mercury(II) activity, respectively. The electrode is employed in analyses of real samples and in potentiometric titrations. It is successfully used for potentiometric titration of humic acids in order to obtain information about the complexing properties of these acids.
Keywords: Copper; Mercury; Ion-selective electrode; Carbon paste modified electrode; Tetraethyl thiuram disulfide; Humic acid;

Electrocatalytic detection of aurothiomalate on carbon electrodes by Alfredo de la Escosura-Muñiz; Marı́a Begoña González-Garcı́a; Agustı́n Costa-Garcı́a (355-363).
A new method to determine the concentration of protein solutions, bovine serum albumin and rabbit IgG anti human IgM (RIgG), has been developed in this work. This method is based on the catalytic effect of the electrodeposited gold on glassy carbon electrodes upon silver electrodeposition. Thus, ionic gold was used as an electroactive label of proteins. Proteins were labelled using a sodium aurothiomalate solution (gold(I) complex). Both solutions were prepared in unbuffered solutions of 0.15 M NaCl, pH 7.5, and the binding was carried out at 37 °C for 24 h. Then, free gold was separated from the labelled protein by a dialysis system, against a 0.15 M NaCl, pH 7.5, solution for 24 h at room temperature. The gold(I) bound to the protein, which was previously adsorbed on the electrode surface, was electrodeposited in 0.1 M HCl at −1.00 V for 5 min, and then oxidised in 0.1 M H2SO4 at a fixed potential, for 1 min. Then, silver electrodeposition at an adequate potential for 1 min followed by anodic stripping voltammetry were carried out in aqueous 1.0 M NH3–2.0×10−4   M AgNO3. Thus, a good linear relationship between the anodic stripping peak and the concentration of labelled protein was found, achieving limits of detection of about 1×10−8   M .The RIgG gold labelling was also used for monitoring an immunological reaction, against a biotinylated anti rabbit IgG which was immobilised on the electrode surface through the streptavidin:biotin interaction, showing that the labelling of RIgG with gold did not affect the antibody:antigen interaction.
Keywords: Ionic gold; Electroactive label; Electrocatalytic deposition of silver; Aurothiomalate; Glassy carbon electrode; Bovine serum albumin; Rabbit IgG;

Irreversible optical test strip for mercury determination based on neutral ionophore by L.F. Capitán-Vallvey; C. Cano Raya; E. López López; M.D. Fernández Ramos (365-372).
A test strip for the determination of mercury in aqueous solution has been developed. It has a circular sensing zone containing all the reagents necessary to produce a selective response to mercury and formed by plasticised PVC incorporating the cation-selective neutral ionophore 1,4,7,10-tetraazacyclododecane, the chromoionophore 9-dimethylamino-5-[4-(15-butyl-1,13-dioxo-2,14-dioxanonadecyl)phenylimino]benzo[a]phenoxazine and tetrabutylammonium tetraphenylborate as lipophilic salt. The measurement principle is based on an ion-exchange mechanism. When the sensor is introduced for a period of time depending on the mercury content into a water sample at a pH of 4.7, there is a colour change from blue to red, making it possible to use absorbance at 670 nm as the analytical signal. All experimental variables that influence the test strip response, especially in terms of selectivity and response time, were studied. The sensor responded linearly to mercury concentration in the range 0.3 and 5.1 μM with a reproducibility in mid-calibration of 1.6% relative standard deviation (R.S.D.) for 60 min agitation. Similarly, it responded linearly to concentrations in the range 7.9–108 μM with a mid-range R.S.D. of 1.8% (for 5 min without agitation). The procedure was applied to the determination of mercury in different types of waters (tap, mineral and spring), validating the results against a reference procedure.
Keywords: Mercury determination; Optical test strip; Neutral ionophore; Water analysis;

Isolation and characterisation of barium sulphate and titanium oxides in monument crusts by José Luı́s Pérez-Rodrı́guez; Marı́a del Carmen Jimenez de Haro; Celia Maqueda (373-377).
Black crusts from historical ornamental materials contain Ba and Ti. These elements are in low proportion, making their determination difficult and especially the characterisation of the phases in which they are present. For this reason, works on the mineralogical composition of the two elements in black crusts is scarce. Thus the isolation, previous to their characterisation, is important for the study of the surface layer in altered monuments.An acid attack for the isolation of barium sulphate and titanium oxides in black crusts from polluted areas has been used. The acid employed is a mixture of HF, HNO3 and HClO4.The residue isolated by acid attack was analysed by energy dispersive X-ray fluorescence and X-ray diffraction. It was characterised, and the percentages of barite (barium sulphate), anatase (titanium oxide), and rutile (titanium oxide) phases present in the surface layers were calculated.
Keywords: Rutile; Anatase; Barite; Black crust; Acid attack; X-ray dispersive energy; X-ray diffraction;

Raman spectroscopy with portable fiber optics microprobe, FT-IR spectroscopy and ion chromatography have been applied to the study of mortars and wall paintings in the church of Santa Marı́a de Hermo (Asturias, North of Spain) before the restoration works. This scientific analysis was performed to compare with a diagnosis report based on restorer’s expertise. The church showed problems of damp as well as clear evidences of flora, fungus and mould presence. The combination of both vibrational spectroscopic techniques made it possible to determine the chromatic palette of the wall paintings composed of: CaCO3, carbon black, red ochre, yellow ochre, minium and cinnabar. In addition, some decay products have been determined, such as nitrate salts, and gypsum.From the conclusions of the scientific analysis the supposedly distemper wall paintings from the XVIIth century were confirmed as frescoes and were then dated back to the XVth century by the art historians. The detachment of the pigment grains from the wall paintings is attributed to the loss of the binding power of CaCO3 by its partial transformation into calcium nitrate due to chemical reactions with nitrates. Clear evidence of nitrate migration from the graveyard behind the northern wall of the church has been determined from the quantification of nitrate salts by ion chromatography.
Keywords: Wall paintings; Pigments; Decaying; Salts;

Author Index (391-393).