Biomedical subjects

I Lavilla

Publications and source records attributed to I Lavilla.

9 recordsLinked to original sources

PubMed2004

Evaluation of distribution, mobility and binding behaviour of heavy metals in surficial sediments of Louro River (Galicia, Spain) using chemometric analysis: a case study.

Contents of total and extractable heavy metals, carbonates, MnO and Fe2O3, organic matter, and matrix components such as SiO2, Al2O3, CaO, Na2O, MgO, TiO2, K2O and P2O5 are used along with principal component analysis (PCA) for studying distribution, mobility and binding behaviour of Cd, Cr, Cu, Ni and Pb in the Louro River (Galicia, Spain). Eleven surficial sediment samples were taken along the beds of the river course. Total metal concentrations were obtained after microwave-assisted digestion whilst extractable metal contents were obtained following a three-stage sequential extraction scheme (i.e. soluble, reducible and oxidisable fractions). Loading plots of heavy metals bound to carbonates, Fe-Mn oxides, organic matter and aluminosilicates allowed determination of binding behaviour. Correlations found indicate that Pb and Cu are mainly discharged from urban wastes, whereas Cr and Ni are from electroplating and galvanizing industries. The occurrence of diffuse pollution sources along the river can account for the binding behaviour of Cd. Metal mobility decreased in the order: Cd > Pb > Cu > Ni > Cr. Despite total contents indicating moderate-to-high heavy metal pollution in this river, metals are mostly distributed in the residual fraction, hence showing a low risk of mobility.

Journal Article↗

PubMed2002

Comparison of the standard SM&T sequential extraction method with small-scale ultrasound-assisted single extractions for metal partitioning in sediments.

A single extraction method based on the reagents employed in the SM&T (standards, measurement and testing programme) sequential extraction scheme for partitioning of Cd, Cr, Cu, Ni, and Pb in sediments has been developed. Small-scale extractions adapted to electrothermal atomic absorption spectrometric determinations (i.e. 25 mg mass in 1 mL extractant) have been used for the first time in conjunction with selective reagents using conventional operating conditions (i.e. conductive heating, magnetic stirring) or ultrasound-assisted extraction. Small-scale slurry preparations were implemented for determination of the residual/total metal content. The methodology developed enabled drastic reduction of extraction times, yielding extractable contents in accordance with those obtained by application of the conventional SM&T method, which can be regarded as a standard method. An important saving in the amount of sample and reagents is also achieved with small-scale extractions. Homogeneity of sediments at the mg level proved acceptable - precision was similar for between-batch and within-batch measurements. Method development was performed with CRM BCR 601 lake sediment for which extractable amounts of several metals are known. An application to a "real-world" sediment is also presented.

Journal Article↗

PubMed2002

Chemical sequential extraction for metal partitioning in environmental solid samples.

A comprehensive review of the sequential extraction schemes for metal fractionation in environmental samples (ie., sediment, soil, sewage sludge, fly ash, etc.) is presented. The review contains more than 400 references and covers principally the literature published over the last decade. The use of each reagent involved in these schemes is looked at critically, and guidelines for their selectivity and extraction capacity are given. The operational character of these schemes is emphasised. Topics such as comparability between sequential extraction schemes of widespread use, harmonisation, acceleration, validation, etc. are addressed and future developments outlined.

Chemistry Techniques, Analytical↗

PubMed2001

Ultrasonic extraction followed by sonolysis-ozonolysis as a sample pretreatment method for determination of reactive arsenic toward sodium tetrahydroborate by flow injection-hydride generation AAS.

A new sample pretreatment method based on ultrasonic extraction in HCI medium and subsequent oxidation of the extracts by sonozone (i.e., sonolysis-ozonolysis) has been developed for determination of reactive arsenic toward sodium tetrahydroborate [mainly As(III) + As(V)] by flow injection-hydride generation atomic absorption spectrometry. This method avoids the use of intensive treatments with concentrated and corrosive acids, high pressures, and temperatures that are inherent with traditional wet or dry ashing procedures and entails reduced waste production and reagent consumption. A sonozone process at room temperature was optimized to break the bond of As to proteins and macromolecular constituents which was an essential requirement for effective reduction by L-cysteine prior to arsine generation. Spiking experiments showed that As(III), As(V), MMA, and DMA were fully recovered from several matrixes on applying the above treatment. On the other hand, a nonreducible As species such as arsenobetaine that is predominant in some biological samples remained unchanged. Application of the method to sediment, soil, fly ash, and plant CRMs demonstrated that, in general, a good agreement existed between certified and found As contents, thereby indicating the absence of nonreducible As forms. Low As recoveries were observed for fish CRMs, as a result of the nondegradability of arsenobetaine by sonozone. The detection limit of As in the samples investigated was in the range 0.19-2.8 microg g(-1).

Animals↗

PubMed2001

Ultrasound-assisted solubilization of trace and minor metals from plant tissue using ethylenediaminetetraacetic acid in alkaline medium.

A simplified and fast sample pretreatment method based on ultrasound-assisted solubilization of metals from plant tissue with ethylenediaminetetraacetic acid in alkaline medium is described. Powdered unknown and certified plant samples (particle size < 50 microns) were slurried in the solubilization medium and subjected to high intensity ultrasonication by a probe ultrasonic processor (20 kHz, 100 W). Metal solubilization can be accomplished within 3 min using a 30% vibrational amplitude and 0.1 M EDTA at pH 10, the supernatant obtained upon centrifugation being used for analysis. The method is applied to several food plants with unknown metal contents and certified plant samples such as CRM GBW07605 tea leaves, BCR CRM 61 aquatic moss and BCR CRM 482 lichen, with good trueness and precision. Intensive treatments with concentrated acids involving total matrix decomposition can be avoided. Metal determination (Ca, Cd, Mg, Mn, Pb and Zn) in the alkaline extracts was carried out by flame and electrothermal atomic absorption spectrometry.

Bryopsida↗

PubMed2000

Room temperature sonolysis-based advanced oxidation process for degradation of organomercurials: application to determination of inorganic and total mercury in waters by flow injection-cold vapor atomic absorption spectrometry

A new oxidation method based on room-temperature ultrasonic irradiation (sonolysis) is proposed for conversion of organomercurials into inorganic mercury and subsequent determination by flow injection-cold vapor atomic absorption spectrometry. This advanced oxidation process eliminates the need for chemical oxidants, high temperature, and pressure for degradation of organomercurials so that total mercury can be determined with sodium tetrahydroborate(III) or tin(II) chloride as reducing agents. Complete oxidations can be accomplished within 3 min, using a 40% sonication amplitude (100 W nominal power) provided by a probe ultrasonic device (20 kHz frequency) and a 1 mol L(-1) HCl liquid medium. The presence of HCl was seen to be necessary for fast oxidation of organomercurials, in contrast to other chemical oxidants such as H2O2 or HNO3 which yielded incomplete oxidation. Further advantages of the proposed method over existing methods which are currently employed for oxidation prior to total Hg determination are the removal of hazardous wastes and the decreased risk of Hg losses by volatilization. Oxidation kinetics indicated a pseudofirst-order reaction with apparent rate constants (k) of 3.2 x 10(-2) and 1.6 x 10(-2) s(-1) for methylmercury and phenylmercury, respectively. Oxidation experiments in the presence of foreign substances acting as OH radical scavengers showed a tolerance at least up to a concentration of 1000 mg L(-1). Likewise, model wastewaters with chemical oxygen demand of up to 1000 mg L(-1) could be processed without diminishing the oxidation efficiency. The method was applied to determination of inorganic and total mercury in simulated wastewaters and spiked environmental waters in combination with selective reduction.

Journal Article↗

PubMed1999

Comparison of digestion methods for determination of trace and minor metals in plant samples.

In this paper, three dissolution methods using pressure digestion vessels (low-, medium-, and high-pressure vessels) for the determination of metals in plant samples are described. The Plackett-Burman saturated factorial design was used to identify the significant factors influencing wet ashing and to select optimized dissolution conditions. The three methods were statistically compared (on-way ANOVA) on the same sample; no significant differences were obtained. In all cases the relative standard deviation values were <3%. The digestion method based on the use of low-pressure vessels and a microwave oven was validated against CRM GBW07605 tea leaves. This method was applied to the determination of Cu, Zn, Mn, Fe, Mg, and Ca in 22 different medicinal, aromatic, and seasoning plants by flame-atomic absorption spectrometry. The concentration intervals of metal in the plants analyzed were the following: Cu, 4 (Allium sativum)-35 (Thea sinensis) microg g(-1); Zn, 7 (Piper nigrum)-90 (Betula alba) microg g(-1); Mn, 9 (Allium sativum)-939 (Caryophylus aromaticus) microg g(-1); Fe, 33 (Allium sativum)-2486 (Anethum graveolens) microg g(-1); Mg, 495 (Allium sativum)-7458 (Ocimum basilicum) microg g(-1); Ca, 386 (Allium sativum)-21500 (Ocimum basilicum) microg g(-1).

Analysis of Variance↗

PubMed1996

Analytical assessment of two sequential extraction schemes for metal partitioning in sewage sludges.

Two sequential extraction schemes were employed for speciation of Cu, Cr, Pb, Ni and Zn in sewage sludges: the conventional Tessier scheme and the sequential extraction scheme proposed by the European Communities Bureau of Reference (BCR). Both sequential extraction schemes were compared in terms of operation time, matrix effects and extraction efficiency. Two sludge samples collected from an urban wastewater processing plant at different seasons were analysed by FAAS for total contents and for extractable metals present in each fraction. Partitioning patterns were obtained for each metal so that metal mobility could be predicted. Both sequential extraction schemes yielded similar performance when extraction efficiencies were compared but matrix effects caused by concomitants were less pronounced in the BCR scheme in comparison with the Tessier scheme.

Calibration↗

PubMedDate not supplied

Determination of selenium in marine biological tissues by transverse heated electrothermal atomic absorption spectrometry with longitudinal Zeeman background correction and automated ultrasonic slurry sampling.

A fast, sensitive, and reliable method for determination of selenium in marine biological tissues by electrothermal atomic absorption spectrometry with slurry sampling was developed. Slurries were prepared from fresh and frozen seafood samples that were previously homogenized, dried, and ground; particle sizes <100 microm were taken for analysis. A 3% (v/v) HNO3 solution containing 0.01% (v/v) Triton X-100 was used as slurry diluent. Slurries were mixed on an automated ultrasonic slurry sampler at 20% amplitude for 30 s just before an aliquot was injected into the furnace. The method was successfully validated against the following certified reference materials: NRCC CRM DORM-2 (Dogfish muscle); NRCC CRM TORT-2 (Lobster hepatopancreas); NRCC CRM DOLT-2 (Dogfish liver); and BCR CRM 278 (Mussel tissue), and was subsequently applied to determination of Se in 10 marine biological samples. The influences of the drying procedure (oven-, microwave-, and freeze-drying), matrix modifier amount, mass of solid material in cup, and pipetting sequence are discussed. The limit of determination of Se was 0.16 microg/g and the repeatability, estimated as between-batch precision, was in the range of 4-8%. Se contents in the samples ranged from 0.6 to 2.8 microg/g. The proposed method should be useful for fast assessment of the daily dietary intake of Se.

Animals↗