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Selenium is an essential element in human and animal metabolism integrated into the catalytic site of glutathione peroxidase (GPX1), an antioxidant enzyme that protects cells from damage caused by reactive oxygen species (ROS). Oxidative stress refers the imbalance between ROS and antioxidant defense systems. It generates alterations of DNA, proteins and lipid peroxidation. The imbalance occurs particularly during ischemia and lack of postmortem perfusion. This mechanism is of relevance in transplant organs, affecting their survival. The aim of this research is to evaluate the effect of seleno-methionine (SeMet) as a protective agent against postmortem ischemia injury in transplant organs. Wistar rats were orally administered with SeMet. After sacrifice, liver, heart and kidney samples were collected at different postmortem intervals (PMIs). SeMet administration produced a significant increase of Se concentration in the liver (65%, p < 0.001), heart (40%, p < 0.01) and kidneys (45%, p < 0.05). Levels of the oxidative stress marker malondialdehyde (MDA) decreased significantly compared to control in the heart (0.21 ± 0.04 vs. 0.12 ± 0.02 mmol g-1) and kidneys (0.41 ± 0.02 vs. 0.24 ± 0.03 mmol g-1) in a PMI of 1-12 h (p < 0.01). After SeMet administration for 21 days, a significant increase in GPX1 activity was observed in the liver (80%, p < 0.001), kidneys (74%, p < 0.01) and heart (35%, p < 0.05). SeMet administration to rats significantly decreased the oxidative stress in the heart, liver and kidneys of rats generated by postmortem ischemia.

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A HPLC coupled with molecular fluorescence (MF) spectrometry method for determination of thimerosal (THM, sodium ethylmercurythiosalicylate, C9 H9 HgNaO2 S), and derivatives is proposed. A sensitization of MF was provoked by UV irradiation of analytes in a home-made photoreactor that served as interface between the LC column and MF spectrometer. This method is applied to determination of THM, ethyl mercury, and thiosalicylic acid in samples of pharmaceutical industry effluents, and waters of La Carolina and Jáchal rivers situated in the center-west side of San Luis city and in the east of San Juan city (Middle West, Argentine) where the effluents are dumped. The LODs calculated on basis of 3σ criterion were 1.8, 5, and 0.05 µmol/L for THM, ethyl mercury, and for thiosalicylic acid, respectively.

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A preconcentration system has been developed to determine inorganic selenium species. Selenium was retained by a column filled with polyvinyl chloride (PVC) with lanthanum hydroxide co-precipitation. Speciation was achieved by selective photoreduction previous Se preconcentration. The retention pH was optimized at 10.0. Two multivariate calibrations and a central composite design were employed for optimization of the system. Sample, reagents and acid flow rates are significant variables affecting the system. Employing HG-ICP-OES as detection, the optimized system reached a detection limit of 0.03µg/L, and an enhancement factor of 14875 (25 for preconcentration system, 595 for hydride generation). To verify the method' accuracy, two certified reference materials, BCR® 414 Plankton & IRMM-804 Rice Flour, were analysed. The system was applied to inorganic selenium speciation in several Argentinean beverages to estimate their selenium contribution to diet.

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An approach to understand vines (Vitis vinifera) defense mechanism against heavy metal stress by isolation and determination of Hg-phytochelatins (PCs) complexes was performed. PCs are important molecules involved in the control of metal concentration in plants. PCs complex toxic metals through -SH groups and stores them inside cells vacuole avoiding any toxic effect of free metals in the cytosol. The Hg-PCs identification was achieved by determination of Hg and S as hetero-tagged atoms. A method involving two-dimensional chromatographic analysis coupled to atomic spectrometry and confirmation by tandem mass spectrometry is proposed. An approach involving size exclusion chromatography coupled to inductively coupled plasma mass spectrometry on roots, stems, and leaves extracts describing Hg distribution according to molecular weight and sulfur associations is proposed for the first time. Medium-low molecular weight Hg-S associations of 29-100 kDa were found, suggesting PCs presence. A second approach employing reversed-phase chromatography coupled to atomic fluorescence spectrometry analysis allowed the determination of Hg-PCs complexes within the mentioned fractions. Chromatograms showed Hg-PC2, Hg-PC3 and Hg-PC4 presence only in roots. Hg-PCs presence in roots was confirmed by ESI-MS/MS analysis.

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Concerns regard watering crops with Hg contaminated waters have arisen worldwide recently. In these sense Hg uptake by Vitis vinifera L. cv. Malbec was evaluated under greenhouse conditions by the administration of Hg(2+) for 4 days through irrigation water (short-term administration). Vines uptake Hg translocating it from roots through stems to leaves. Roots accumulated the higher Hg concentration. Hg in stems and leaves was accumulated mostly as organic Hg, bind to different moieties. Size exclusion chromatography (SEC) and ion pair chromatography (IPC) were employed to reach insights into these ligands. Hg is distributed mainly in high molecular weight fractions of 669 kDa in vine plants. In stems and leaves, Hg-S associations were found in 669 and 66 kDa fractions. Hg-S association at 66 kDa suggests a possible protein or peptide binding affecting vines normal physiology. Since Hg contamination through organomercurials is more harmful than Hg(2+) itself, methyl mercury, dimethyl mercury, and phenyl mercury, more toxic Hg species were evaluated with negative results.

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Biosorption is a term that usually describes the removal of heavy metals from an aqueous solution through their passive binding to a biomass. Bacteria, yeast, algae and fungi are microorganisms that have been immobilized and employed as sorbents in biosorption processes. The binding characteristics of microorganisms are attributed to functional groups on the surface providing some features to the biosorption process like selectivity, specificity and easy release. These characteristics turn the biosorption into an ideal process to be introduced in solid phase extraction systems for analytical approaches. This review encompasses the research carried out since 2000, focused on the employment of biosorption processes as an analytical tool to improve instrumental analysis. Since aminoacids and peptides as synthetic analogues of natural metallothioneins, proteins present in the cell wall of microorganisms, have been also immobilized on solid supports (controlled pore glass, carbon nanotubes, silica gel polyurethane foam, etc.) and introduced into solid phase extraction systems; a survey attending this issue will be developed as well in this review.

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A simple non-chromatographic method for the determination of mercury (Hg(2+)), methylmercury (MeHg(+)), dimethylmercury (Me(2)Hg), and phenylmercury (PhHg(+)) employing atomic fluorescence spectrometry (AFS) as detection technique was developed. Mercury species showed a particular behavior in the presence of several reagents. In a first stage SnCl(2) was employed for Hg(2+) determination; in a second step, [Hg(2+)+PhHg(+)] concentration was determined using SnCl(2) and UV radiation. MeHg(+) decomposition was prevented adding 2-mercaptoethanol. In a third stage, [Hg(2+)+PhHg(+)+MeHg(+)] concentration was determined using K(2)S(2)O(8). Finally, the four species were determined employing NaBH(4). Reagents concentration and flow rates were optimized. The extraction technique of mercury species involved the use of 2-mercaptoethanol as ion-pair reagent. The limits of detection for Hg(2+), PhHg(+), MeHg(+), and Me(2)Hg were 1, 40, 68, and 99 ng L(-1) with a relative standard deviation of 1.5, 3.1, 4.7 and 5.8%, respectively. Calibration curve was linear with a correlation factor equal to 0.9995. The method was successfully applied to the determination of the mercury species in two Antarctic materials: IRMM 813 (Adamussium colbecki) and MURST-ISS-A2 (Antarctic Krill).

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An approach for the separation and determination of inorganic thallium species is described. A new sorbent, L-tyrosine-carbon nanotubes (L-tyr-CNTs), was used and applied to the analysis of tap water samples. At pH 5.0, L-tyr was selective only towards Tl(III), while total thallium was determined directly by stabilized temperature platform furnace-electrothermal atomic absorption spectrometry (STPF-ETAAS). The Tl(III) specie, which was retained by L-tyrosine, was quantitatively eluted from the column with 10% of nitric acid. An on-line breakthrough curve was used to determine the column capacity, which resulted to be 9.00 micromol of Tl(III) g(-1) of L-tyr-CNTs with a molar ratio of 0.14 (moles of Tl bound to moles of L-tyr at pH 5). Transient peak areas revealed that Tl stripping from the column occurred instantaneously. Effects of sample flow rate, concentration and flow rate of the eluent, and interfering ions on the recovery of the analyte were systematically investigated. The detection limit for the determination of total thallium (3sigma) by STPF-ETAAS was 150 ng L(-1). The detection limit (3sigma) for Tl(III) employing the separation system was 3 ng L(-1), with an enrichment factor of 40. The precision of the method expressed as the relative standard deviation (RSD) resulted to be 3.4%. The proposed method was applied to the speciation and determination of inorganic thallium in tap water samples. The found concentrations were in the range of 0.88-0.91 microg L(-1) of Tl(III), and 3.69-3.91 microg L(-1) of total thallium.

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A study was performed to assess the performance of aminoacids immobilized on carbon nanotubes (CNTs) for their employment as a sorbent for solid phase extraction systems. An immobilization method is introduced and the aminoacid L-tyrosine was chosen as a case study. A spectrophotometric study revealed the amount of aminoacid immobilizated on CNTs surface, and it turned to be of 3174 micromol of L-tyrg(-1). The material was tested for Co retention using a minicolumn inserted in a flow system. At pH 7.0, the amount of Co retained by the column was of 37.58+/-3.06 micromol Co g(-1) of CNTs. A 10% (v/v) HNO(3) solution was chosen as eluent. The pH study revealed that Co binding increased at elevated pH values. The calculation of the mol ratio (moles of Co bound at pH 9 to moles of l-tyr) turned to be 3:1. The retention capacity was compared to other bivalent cations and showed the following tendency: Cu(2+)>Ni(2+)>Zn(2+)>>Co(2+). The analytical performance was evaluated and an enrichment factor of 180 was obtained when 10 mL of 11.37 microg L(-1)Co solution was loaded onto the column at pH 9.0; reaching a limit of detection (LoD) of 50 ng L(-1). The proposed system was successfully applied to Co determination in QC-LL2 standard reference material (metals in natural water).

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A study was undertaken to ascertain the analytical capabilities of combined ICP-OES with ultrasonic nebulization to perform on-line preconcentration and speciation of inorganic V species in urine samples using a micro-column packed with l-methionine immobilized on controlled pore glass (CPG) as solid phase extractant. At pH 5.0, l-methionine is selective only towards V(V) while, total vanadium was quantitatively adsorbed by the solid phase at pH 9.0 [as V(V)] due to V(IV) oxidation in alkali media. Vanadium species retained by l-methionine were quantitatively eluted from the column with 10% HCl. Effects of acidity, sample flow rate, concentration of eluent and interfering ions on the recovery of the analytes have been systematically investigated. The detection limit (3sigma) of V is 0.008ngmL(-1) for USN-ICP-OES with an enhancement factor of 900 (10 for USN and 90 for l-methionine), and the relative standard deviation (R.S.D.) is better than 2%. The proposed method has been applied to the determination of inorganic V(V) and V(IV) in urine.

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A study was undertaken to ascertain the analytical capabilities of L-methionine immobilized on controlled pore glass for Sb preconcentration and speciation. A fully automated on-line system, implemented with hydride generation (HG) and inductively coupled plasma optical emission spectrometry (ICP OES), was used. Sb(III), at pH 10 was selectively retained in the column containing the immobilized aminoacid, while Sb(V) was not retained at all. A 30% HCl solution was used as eluent agent. Prior to total Sb determination, a pre-reduction step with thiourea was necessary. An on-line pH adjusting and pre-reduction of Sb(V) was achieved in a fully automated system. The detection limit for the preconcentration of 10 mL of an aqueous solution was 70 ng L(-1) with a relative standard deviation of 2%. An enrichment factor of 20 was achieved when 10 mL of sample was passed through the system, reaching a throughput of 23 samples per hour. The method was successfully applied to the determination of Sb(III) and total Sb in urine.

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