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Carmen Cámara

Publications and source records attributed to Carmen Cámara.

17 recordsLinked to original sources
PubMed2006

Current perspectives in analyte extraction strategies for tin and arsenic speciation.

Nowadays, reliable and robust detectors can be considered standard laboratory instrumentation, which, for most of the elements provide quantitation limits in the lower ng/g range. Despite these advances in detector technology, sample preparation is by far the most important error source in modern analytical method development and can be judged as the "Achilles' heel" of any analytical process regarding reliability of the obtained results and time consumption. The aim of the present review is to highlight modern trends for tin and arsenic speciation, as these analytes can be considered as models for challenges in modern method development in this field. First background information, legislative aspects and current needs are elucidated. Then the role of sample treatment within the process of method development in speciation is discussed, followed by a presentation of modern extraction techniques, matching the requirements for arsenic and tin speciation analysis: to provide mild conditions in order to ensure species preservation, to improve species recovery, to enhance sample throughput and to be suitable for hyphenation with chromatographic separation systems. The review includes applications on tin and arsenic speciation, covering the period of 2001-2006.

Analytic Sample Preparation Methods↗
PubMed2006

Identification of selenium species in selenium-enriched Lens esculenta plants by using two-dimensional liquid chromatography-inductively coupled plasma mass spectrometry and [77Se]selenomethionine selenium oxide spikes.

Selenium speciation in Se-enriched Lens esculenta grown in hydroponic culture containing inorganic selenium as Na(2)SeO(3) and Na(2)SeO(4) was performed. After 16 days of growth, the plants were collected and divided in two parts, roots and stems and then analysed to identify and quantify selenium species. Speciation studies of the enzymatic extracts were carried out by using anion-exchange (PRP-X100) and size-exclusion/ion-exchange (Shodex Asahipak) columns coupled to inductively coupled plasma mass spectrometry (ICP-MS). The need of using two independent chromatographic mechanisms for unambiguous species identification is demonstrated. Moreover, the use of a [(77)Se]selenomethionine selenium oxide spike turned out to be critical to discriminate between selenium selenomethioine selenium oxide and selenocysteine.

Chromatography, Liquid↗
PubMed2006

Selenium long-term administration and its effect on mercury toxicity.

An in vivo experiment was conducted to assess selenium bioaccumulation and bioaccessibility through the food chain and its effect on Hg toxicity. For this purpose 72 chickens were fed under different controlled conditions. Chickens were exposed to a common basal diet or a diet supplemented with Hg(II), MeHg, and Se(IV). Enzymatic digestion (feed, chicken muscle, liver, and kidney) as well as simulated human gastric and intestinal digestion (chicken muscle) led to the identification of selenomethionine (SeMet) in all the samples analyzed. Therefore, although chickens have no efficient mechanism for SeMet synthesis they can be considered as a source of SeMet due to its diet and the plant-animal food chain. The kidneys were the target organ for both total Se and SeMet in chickens (1604 +/- 136 and 128 +/- 6 microg kg(-1), respectively), but the greatest body store, among the tissues studied, was the muscle in both cases (84-96% of total Se). Long-term administration of inorganic and organic mercury did not alter SeMet distribution significantly. The antagonistic effect of Se on Hg toxicity by favoring MeHg demethylation is discussed.

Animals↗
PubMed2006

Selenium species bioaccessibility in enriched radish (Raphanus sativus): a potential dietary source of selenium.

An in vitro gastrointestinal method was employed to predict the potential bioavailability of selenium and its species from radish, belonging to the Brassicaceae family, grown in hydroponics media in the presence of inorganic selenium, such as Na2SeO3 and Na2SeO4. A low transformation of Se into organic forms was observed in radish plants grown in Se(VI)-enriched culture media. On the contrary, in those plants exposed to selenite, >95% of the total selenium was found as selenocystine (SeCys2), selenomethionine (SeMet), and Se-methylselenocysteine (SeMetSeCys). The concentrations of these species in fresh samples remained almost unaltered after a simulated gastrointestinal digestion. Therefore, a high selenium content of Se-methylselenocysteine (65%), previously reported as a cancer chemopreventive species, remained in the potentially bioabsorbable fraction. As these plants usually undergo a short development cycle, these results suggest that radish enriched in selenite could be a good choice as an organoselenium supplement for the human diet and animal feed.

Biological Availability↗
PubMed2006

Focused ultrasound and molecularly imprinted polymers: a new approach to organotin analysis in environmental samples.

There is a high interest in speciation of organotin compounds (OTCs) in biota and marine sediment samples, due to their influence in the transmission of the contamination in the trophic chain. Sample treatment is still the most "compromising" step of speciation analysis. Extraction methods are in general time-consuming due to long extraction times and several analytical steps involved. In addition, in most cases there are problems of low recovery, especially for MBT. These drawbacks, added to the high matrix effects generally present in biota samples, make the sample treatment for organotin analysis a serious challenge for environmental issues. Here we present a novel, fast and efficient two steps method for organotin speciation in mussel and oyster tissue as well as in marine sediments. The first step based on the use of ultrasonic probe extraction for species leaching allowed us to quantitatively extract these compounds in a few minutes. Matrix interferences drastically decreased by applying a clean-up step based on the use of an imprinted polymer especially designed for tributyltin (TBT). This procedure increased accuracy and precision of the GC-FPD analysis and improving the limit of detection, Besides, this new method prevents the use of standard addition calibration method, which is mandatory without the clean-up step. The optimization and validation has been performed by using three reference materials: mussel tissue CRM-477, oyster candidate T-38 and sediment PACS-2.

Animals↗
PubMed2005

Recent developments in solid-phase microextraction coatings and related techniques.

During the last decade, solid-phase microextraction (SPME) has gained widespread acceptance for analyte matrix separation and preconcentration. Relatively few data are currently available dealing with in-house production of fibres with tailor-made properties to be used for SPME, though recently the number of publications evaluating new coatings has been considerably growing. This review, centred on publications that appeared during the last five years, is resuming different approaches which can be used for fibre production and further summarises alternative techniques closely related to SPME, such as in-tube extraction or single-drop microextraction (SDME). The aim is to give the reader a concise overview of recent developments in new coating procedures and materials, including the respective applications.

Chemical Fractionation↗
PubMed2005

Effect of animal feed enriched with Se and clays on Hg bioaccumulation in chickens: in vivo experimental study.

An in vivo experiment was conducted to evaluate the effects of sodium selenite, sepiolite, and bentonite on inorganic mercury (Hg) and methylmercury (MeHg) bioaccumulation. For this purpose 160 chickens were fed under different controlled conditions. Chickens were exposed to Hg(II) and MeHg added to feed with or without selenium or clays supplementation. No significant differences were observed in the voluntary intake and feed/gain conversion rates. The target organs of Hg(II) and MeHg in chickens were the liver and kidney, respectively, but the greatest body store was the muscle in both cases. A higher bioaccumulation for MeHg than for Hg(II) was observed. The results showed that addition of sodium selenite, sepiolite, or bentonite induced a decrease of up to 60-100% in the inorganic mercury bioabsorption. Bentonite addition to a MeHg-containing diet also caused a decrease in organic mercury bioaccumulation (29-67%). On the other hand, inorganic selenium and sepiolite did not decrease MeHg accumulation.

Aluminum Silicates↗
PubMed2005

Quantification and speciation of mercury and selenium in fish samples of high consumption in Spain and Portugal.

Mercury (Hg) and selenium (Se) determinations were carried out to evaluate human exposure to those elements through fish consumption in Spain and Portugal. Atomic fluorescence spectroscopy (AFS) was applied in a cold vapor mode for total mercury quantification and was also hyphenated to gas chromatography (GC) to achieve the speciation of organomercurial species in fish samples. The results obtained show the highest concentration of Hg in swordfish and tuna (0.47+/-0.02 and 0.31+/-0.01 microg g-1, respectively), and a much lower concentration in sardine, mackerel shad, and octopus (0.048+/-0.002, 0.033+/-0.001, and 0.024+/-0.001 microg g-1, respectively). The determination of alkyl mercury compounds revealed that 93-98% of mercury in the fish samples was in the organic form. Methylmercury (MeHg) was the only species found in the three fish species with higher mercury content. Total selenium concentration was high in sardine, swordfish, and tuna (0.43+/-0.02, 0.47+/-0.02, and 0.92+/-0.01 microg g-1, respectively), but low in mackerel shad and octopus (0.26+/-0.01 and 0.13+/-0.01 microg g-1, respectively). Speciation of selenium compounds was done by high-performance liquid chromatography in conjunction with inductively coupled plasma mass spectrometry (LC-ICP-MS). Selenomethionine (SeMet) was the only selenium compound identified in the fish samples with higher selenium content. Among the fish species studied, sardine had the most favourable Se:Hg and SeMet:MeHg molar ratios; therefore, its consumption seems to be preferable.

Animals↗
PubMed2004

Enzymatic probe sonication extraction of Se in animal-based food samples: a new perspective on sample preparation for total and Se speciation analysis.

This paper describes a fast, simple and novel extraction method for total selenium and selenium species determination in food samples. Parameters influencing extraction, such as sonication time, extracting media, temperature, sample mass, ultrasound amplitude and sample/enzyme mass ratio were investigated. The enzymatic hydrolysis proposed, enhanced by probe sonication, allowed the quantitative extraction of selenium in chicken muscle, liver, kidney and feed (97, 93, 95 and 102%, respectively) in 2 min, maintaining the original Se-species integrity. Total Se content of the samples was determined using inductively coupled plasma mass spectrometry. Se-species were identified and quantified using high-performance liquid chromatography in conjunction with inductively coupled plasma mass spectrometry. Chromatographic analyses were carried out under two chromatographic conditions and led to the identification of SeMet in all samples. The accuracy of the proposed method was assessed using certified reference materials as well as microwave digestion. Potential advantages of the proposed method over traditional hydrolysis are speed, simplicity and safety of the procedure.

Animal Feed↗
PubMed2004

Establishment of selenium uptake and species distribution in lupine, Indian mustard, and sunflower plants.

Selenium has been recognized as essential for all mammals; therefore, its concentration level and speciation are of great concern. Plants are one of the main sources of selenium in the diet. Thus, inorganic selenium uptake and its transformation in different species were evaluated in Indian mustard (Brassica juncea), sunflower (Helianthus annus), and white lupine (Lupinus albus). More than 1.2 g x kg(-)(1) (dry matter) of Se was found in the aerial part of Indian mustard when growing on 1 mg x L(-)(1) of Se as Na(2)SeO(4), and approximately half this amount was determined in the leaves of the lupine, which is still quite high. Selenomethionine was the main selenium-containing amino acid identified in most of the extracts by HPLC-ICP-MS. The higher values were 6.8 and 14.5 mg x kg(-)(1) (expressed as Se in dry matter) in the leaves of lupine and sunflower, respectively. This is of great importance because some authors have considered the combination of this enriched material with non-enriched food as a source of selenium supplementation.

Chromatography, High Pressure Liquid↗
PubMed2003

[Autoimmune lymphoproliferative syndrome: molecular diagnosis in two families].

BACKGROUND AND OBJECTIVE: The autoimmune lymphoproliferative syndrome (ALPS) is a disorder caused by a defect in lymphocytes' apoptosis and characterized by non malignant lymphoproliferation, autoimmune features and increased TCR alpha + CD4CD8 cells. Most patients have a mutation in the TNFRSF6 gene, which encodes the Fas protein. Our aim was to identify mutations in this gene in two families with possible ALPS cases. PATIENTS AND METHOD: Two patients with suspicion of ALPS, belonging to two unrelated families, were studied. To confirm such a diagnosis, immunoglobulin quantification, cellular phenotypic analysis by flow cytometry, IL-10 quantification, an apoptosis study, and molecular analysis were performed. RESULTS: Both patients showed hypergammaglobulinemia and an increased percentage of TCR alpha + CD4CD8 cells (family A patient: 14%; family B patient: 4.25%). In family A, in vitro Fas-mediated apoptosis was absent in the patient and markedly reduced in his father. In this family, both the patient and his father were heterozygous for the Fas mutation T1045C (Leu 268 Pro). The family B patient and her mother showed the Fas mutation G943T (Arg 234 Leu), both being heterozygous for it too. Both mutations are located in exon 9 of TNFRSF6 gene, affecting the death domain of the Fas protein. CONCLUSIONS: The molecular study of these families confirms a diagnosis of ALPS and suggests that the causing defect of this syndrome is compatible with an autosomal dominant inheritance with incomplete penetrance.

Autoimmune Diseases↗
PubMed2003

Evaluation of stability of arsenic species in rice.

Although most edible vegetables do not accumulate As at a high rate, rice, carrots and certain others are exceptions. In addition to nutritional or toxicological considerations, the relatively high level and variety of As species present in rice make it a very suitable matrix for a candidate reference material representative of terrestrial biological samples.An analytical procedure was developed for As speciation in rice based on the use of a 1:1 methanol-water mixture for species extraction, an anion Hamilton PRPX-100 column (at pH 6, and phosphate mobile phase 10 mM), and a cation Hamilton PRP-X200 column (at pH 2.8 in pyridine formiate 4 mM) for species separation and final determination by HPLC-ICP-MS. The detection limits for dry flour rice expressed as As were 2 and 3 ng g(-1) for As(III) and AsB on the cation column and 3, 6 and 5 ng g(-1) for As(V), MMA and DMA, respectively, on the anion column. The methodology developed was applied to check the stability of As species in the water-methanol extract and also under different processing steps and storage time and temperature conditions. It was demonstrated that the As species in the water-methanol extracts stored at +4 degrees C remained stable for at least one month. Once the rice grains are ground, the MMA and As(V) species are not stable under any storage conditions probably due to microbiological activity. When ground rice is gamma-irradiated species remain stable although the AsB does not appear.

Arsenic↗
PubMed2003

The effect of the presence of volatile organoselenium compounds on the determination of inorganic selenium by hydride generation.

As a result of microbiological activity it is possible to find dimethylselenium (DMSe) and dimethyldiselenium (DMDSe) in a wide type of environmental samples, such as soils, sediments, sewage sludges and plants where methylation can take place. Selenium determination by hydride-generation (HG) techniques requires its presence as Se(IV). Consequently, inorganic speciation by hydride generation techniques is done by first determining Se(IV) and then, after reduction of Se (VI) to Se(IV), the total selenium. Therefore, the concentration of Se (VI) is evaluated as the difference between total inorganic selenium and Se(IV). In the present work it could be demonstrated that DMSe and DMDSe are forming other volatile species by reaction with sodium borohydride, applying the same reduction condition as for inorganic selenium. These species are subsequently detected by several atomic techniques (atomic absorption AAS, atomic fluorescence AFS and inductively coupled plasma-mass spectrometry ICP-MS). The error that their presence can cause in determination of inorganic selenium has been evaluated. The magnitude of this error depends on the specific analytical detector used.The coupling of pervaporation-atomic fluorescence is proposed for the identification of these species and pervaporation-gas chromatography-atomic fluorescence for their individual quantification.

Journal Article↗
PubMed2002

Stability study of As(III), As(V), MMA and DMA by anion exchange chromatography and HG-AFS in wastewater samples.

The stability of arsenic species (arsenate [As(V)], monomethylarsonate [MMA], dimethylarsinate [DMA] and arsenite [As(III)]) in two types of urban wastewater samples (raw and treated) was evaluated. Water samples containing a mixture of the different arsenic species were stored in the absence of light at three different temperatures: +4 degrees C, +20 degrees C and +40 degrees C. At regular time intervals, arsenic species were determined by high performance liquid chromatography (HPLC)-hydride generation (HG)-atomic fluorescence spectrometry (AFS). The experimental conditions for the separation of arsenic species by HPLC and their determination by AFS were directly optimised from wastewater samples. As(III), As(V), MMA and DMA were separated on an anion exchange column using phosphate buffer (pH 6.0) as the mobile phase. Under these conditions the four arsenic species were separated in less than 10 min. The detection limits were 0.6, 0.9, 0.9 and 1.8 micro g L(-1) for As(III), DMA, MMA and As(V), respectively. As(V), MMA and DMA were found stable in the two types of urban wastewater samples over the 4-month period at the three different temperatures tested, while the concentration of As(III) in raw wastewater sample decreased after 2 weeks of storage. A greater stability of As(III) was found in the treated urban wastewater sample. As(III) remained unaltered in this matrix at pH 7.27 over the period studied, while at lower pH (1.6) losses of As(III) were detected after 1 month of storage. The results show that the decrease in As(III) concentration with time was accompanied by an increase in As(V) concentration.

Arsenic↗
PubMed2002

Capability of diatomaceous earth to preconcentrate and store Pb and Cr: on-line determination by FI-FAAS.

The diatomaceous earth (DE) has an important ability to retain metals such as Cd, Cr, Mn and Pb, which can be used for their stabilization in the environment and for analytical purposes. In this paper a fast on-line preconcentration method for the determination of Cr and Pb in waters by flow injection flame atomic absorption spectrometry is described. Preconcentration was based on the retention of Cr and Pb on a DE immobilized in silica gel at pH 3.0 and subsequent elution with 200 microL of 3 mol L(-1) HCl. The preconcentration factors were 100 and 150 for Pb and Cr respectively, for 16 mL water sample volume. The detection limits under these conditions were 3 ng mL(-1) and 1 ng mL(-1) for Pb and Cr, respectively. The stability of Cr and Pb retained on silica gel-DE columns was established. Silica gel-DE microcolumns with the retained analytes were stored for 2 months at two different temperatures: 4 degrees C and room temperature. At regular time intervals, both metals were eluted and quantified. The results showed the potential of the procedure for sampling and storing water samples for subsequent metal determination, avoiding the problems associated with maintaining species integrity in aqueous solution, and the possibility to of decontaminating polluted spaces.

Calibration↗
PubMed2002

CD106 and activated-CD29 are expressed on myelomatous bone marrow plasma cells and their downregulation is associated with tumour progression.

Malignant plasma cells (PC) from multiple myeloma (MM) patients characteristically home to the bone marrow (BM). High numbers of tumour cells are found in the peripheral blood (PB) only at end-stage disease (secondary plasma cell leukaemia, PCL) in a minority of patients. Using flow cytometric and fluorescence in situ hybridization (FISH) analysis, a high percentage of tumoral BM PC from untreated patients was found to express CD106. In addition, these cells also expressed an activated form of CD29, as determined using the CD29 activation reporter monoclonal antibody HUTS-21. Adhesion-binding experiments showed that CD106+-activated CD29+ BM PC from these patients adhered to fibronectin (FN) in a CD29/CD49d-dependent manner. In contrast, marrow PC from progressive patients and BM or circulating malignant cells from secondary PCL patients expressed lower levels or were negative for CD106 and activated CD29, respectively, with a decreased or zero ability to adhere to FN. The expression of constitutive CD29 and CD49d, however, was similar during disease progression. We conclude that BM myelomatous cells co-express CD106 and a functionally active form of CD29. Moreover, our results suggest that the loss of expression and/or function of these antigens are associated with the progression of MM and may explain the exit of tumoral cells from the BM.

Bone Marrow Cells↗