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Viabilidade da medida de elementos-traço em soro sanguíneo para diagnóstico de melanoma; Trace elements measurement in blood sérum for the diagnosis of melanoma a viability study

Santos, Suene Bernardes dos
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 01/10/2012 PT
Relevância na Pesquisa
37.30601%
A medida e o controle de elementos químicos, majoritários ou traço, em tecidos e fluídos biológicos, vem sendo utilizada há muito tempo para diagnósticos médicos, em avaliações de saúde, estado nutricional e para prevenção e acompanhamento de doenças. Em muitos casos tal relação já foi solidamente estabelecida, mas no estudo de neoplasias, ainda se busca relação entre teores químicos elementares e vários tipos (ou estágios) de câncer. Nesse tipo de estudo utilizam-se métodos espectroscópicos multi-elementares de altíssima sensibilidade ainda não disponíveis rotineiramente em laboratórios clínicos. Neste trabalho, buscaram-se alterações na concentração de elementos químicos majoritários e traço em soro sanguíneo de pacientes com melanoma, por meio de análises pelos métodos PIXE e HR-ICPMS como auxiliar de diagnóstico desta neoplasia, uma vez que sua detecção em estágios iniciais aumenta a probabilidade de recuperação. A técnica PIXE (Proton Induced X-ray Emission) de análise multi-elementar baseia-se na detecção de raios X característicos, enquanto o HR-ICPMS (High Resolution Inductively Coupled Plasma Mass Spectrometry) é um espectrômetro de massa de alta resolução. As amostras de sangue de 30 pacientes e 116 doadores sadios foram coletadas no Hospital São Paulo (protocolos CEP 1036/08 UNIFESP) em tubos de vidro sem aditivos...

Effects of dietary trace mineral sources and levels fed to layers in their second laying cycle on the quality of eggs stored at different temperatures and for different periods

Saldanha, ESPB; Garcia, Edivaldo Antônio; Pizzolante, CC; Gonçalves, Heraldo Cesar; Faittarone, ABG; Sechinato, AS; Laganá, C
Fonte: Fundação APINCO de Ciência e Tecnologia Avícolas Publicador: Fundação APINCO de Ciência e Tecnologia Avícolas
Tipo: Artigo de Revista Científica Formato: 223-231
ENG
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37.40878%
This study aimed at evaluating the effects of trace mineral levels and sources supplemented to diets fed to semi-heavy layers in their second laying cycle on the quality of eggs stored for 14 days at different temperatures. The experimental diets consisted of the inclusion of inorganic trace minerals (T1 - control: 100% ITM) and five supplementation levels of organic trace minerals (carboaminophopho chelates) (110, 100, 90, 80, and 70% OTM). Trace mineral inclusion levels (mg/kg feed) were: T1: control - 100% ITM: Zn (54), Fe (54), Mn (72), Cu (10), I (0.61) Se (0.3); T2 - 110% OTM: Zn (59.4), Fe (59.4), Mn (79.2), Cu (11.88), I (1.21) Se (0.59); T3 - 100%: OTM: Zn (54), Fe (54), Mn (72), Cu (10.8), I (1.10) Se (0.54); T4 - 90% OTM: Zn (48.6), Fe (48.6), Mn (64.8), Cu (9.72), I (0.99) Se (0.49); T5 - 80% OTM: Zn (43.2), Fe (43.2), Mn (57.6), Cu (8.64), I (0.88), Se (0.43); T6 - 70% OTM: Zn (37.8), Fe (37.8), Mn (50.4), Cu (7.56), I (0.77) Se (0.38). A completely randomized experimental design in a split-plot arrangement with 60 treatments of four replicates each was applied. The combination of six diets versus storage temperature (room or under refrigeration) was randomized in plots, whereas the sub-plots consisted of storage times (0...

Analysis of Steroids using Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry-Mass Spectrometry (SPME-GC-MS-MS)

Chopra, Shilpi; Lima Gomes, Paulo Clairmont Feitosa de; Dhandapani, Ramkumar; Snow, Nicholas H.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 105-116
POR
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46.86055%
Direct immersion SPME-GC-MS-MS was used for the analysis of steroids in water at part-per-trillion(ppt) and lower concentrations. The method was validated and extended to real sample analysis. The method were linear from 0.01 to 5 ng/ml with precision less than 10% relative standard deviation for a steroid mixture at 1 ng/ml. Limit of quantitation and limit of detection was found to be 200- 1200 pg/L and 30-200 pg/L respectively and recoveries ranged from 88-103 %. To understand the extraction efficiency of the fiber, a depletion study was performed. The fiber/ sample partition coefficients for the steroids were determined to be 1.0 x 104 to 1.5 x 104 . The extraction was performed without derivatization or the use of an internal standard. SPMEGC-MS-MS effectively demonstrated ultra-trace level detection of steroids in water.

Flow-through solid-phase based optical sensor for the multisyringe flow injection trace determination of orthophosphate in waters with chemiluminescence detection

Morais, Inês P.A.; Miró, Manuel; Manera, Matias; Estela, José Manuel; Cerdà, Víctor; Souto, M. Renata S.; Rangel, António O.S.S.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2004 ENG
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37.40862%
In this work, a novel flow-through solid-phase based chemiluminescence (CL) optical sensor is described for the trace determination of orthophosphate in waters exploiting the multisyringe flow injection analysis (MSFIA) concept with multicommutation. The proposed time-based injection flow system relies upon the in-line derivatisation of the analyte with ammonium molybdate in the presence of vanadate, and the transient immobilisation of the resulting heteropolyacid in a N-vinylpyrrolidone/divinylbenzene copolymer packed spiral shape flow-through cell located in front of the window of a photomultiplier tube. The simultaneous injection of well-defined slugs of luminol in alkaline medium and methanol solution towards the packed reactor is afterwards performed by proper switching of the solenoid valves. Then, the light emission from the luminol oxidation by the oxidant species retained onto the sorbent material is readily detected. At the same time, the generated molybdenum-blue compound is eluted by the minute amount of injected methanol, rendering the system prepared for a new measuring cycle. Therefore, the devised sensor enables the integration of the solid-phase CL reaction with elution and detection of the emitted light without the typical drawbacks of the molybdenum-blue based spectrophotometric procedures regarding the excess of molybdate anion...

Modern directions for potentiometric sensors

Bakker,Eric; Chumbimuni-Torres,Karin
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 EN
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46.75659%
This paper gives an overview of the newest developments of polymeric membrane ion-selective electrodes. A short essence of the underlying theory is given, emphasizing how the electromotive force may be used to assess binding constants of the ionophore, and how the selectivity and detection limit are related to the basic membrane processes. The recent developments in lowering the detection limits of ISEs are described, including recent approaches of developing all solid state ISEs, and breakthroughs in detecting ultra-small quantities of ions at low concentrations. These developments have paved the way to use potentiometric sensors as in ultra-sensitive affinity bioanalysis in conjunction with nanoparticle labels. Recent results establish that potentiometry compares favorably to electrochemical stripping analysis. Other new developments with ion-selective electrodes are also described, including the concept of backside calibration potentiometry, controlled current coulometry, pulsed chronopotentiometry, and localized flash titration with ion-selective membranes to design sensors for the direct detection of total acidity without net sample perturbation. These developments have further opened the field for exciting new possibilities and applications.

Enhancement of canthaxanthin production from Dietzia natronolimnaea HS-1 in a fed-batch process using trace elements and statistical methods

Nasri Nasrabadi,M. R.; Razavi,S. H.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2010 EN
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Under fed-batch process conditions, the statistical analysis of trace elements was performed by application of Plackett-Burman design (for screening tests) and response surface methodology (for predicting the optimal points) to achieve the highest level of canthaxanthin production from Dietzia natronolimnaea HS-1. Plackett-Burman design was conducted on eleven trace elements (i. e., aluminum, boron, cobalt, copper, iron, magnesium, manganese, molybdenum, selenium, vanadium and zinc) to select out elements that significantly enhance the canthaxanthin production of D. natronolimnaea HS-1. Plackett-Burman design revealed that Fe3+, Cu2+ and Zn2+ ions had the highest effect on canthaxanthin production of D. natronolimnaea HS-1 (P<0.05). These three elements were used for further optimization. By means of response surface methodology for the fed-batch process, the optimum conditions to achieve the highest level of canthaxanthin (8923±18 µg/L) were determined as follow: Fe3+ 30 ppm, Cu2+ 28.75 ppm and Zn2+ 27 ppm.

Effects of dietary trace mineral sources and levels fed to layers in their second laying cycle on the quality of eggs stored at different temperatures and for different periods

Saldanha,ESPB; Garcia,EA; Pizzolante,CC; Gonçalves,HC; Faittarone,ABG; Sechinato,AS; Laganá,C
Fonte: Fundação APINCO de Ciência e Tecnologia Avícolas Publicador: Fundação APINCO de Ciência e Tecnologia Avícolas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2010 EN
Relevância na Pesquisa
37.40878%
This study aimed at evaluating the effects of trace mineral levels and sources supplemented to diets fed to semi-heavy layers in their second laying cycle on the quality of eggs stored for 14 days at different temperatures. The experimental diets consisted of the inclusion of inorganic trace minerals (T1 - control: 100% ITM) and five supplementation levels of organic trace minerals (carboaminophopho chelates) (110, 100, 90, 80, and 70% OTM). Trace mineral inclusion levels (mg/kg feed) were: T1: control - 100% ITM: Zn (54), Fe (54), Mn (72), Cu (10), I (0.61) Se (0.3); T2 - 110% OTM: Zn (59.4), Fe (59.4), Mn (79.2), Cu (11.88), I (1.21) Se (0.59); T3 - 100%: OTM: Zn (54), Fe (54), Mn (72), Cu (10.8), I (1.10) Se (0.54); T4 - 90% OTM: Zn (48.6), Fe (48.6), Mn (64.8), Cu (9.72), I (0.99) Se (0.49); T5 - 80% OTM: Zn (43.2), Fe (43.2), Mn (57.6), Cu (8.64), I (0.88), Se (0.43); T6 - 70% OTM: Zn (37.8), Fe (37.8), Mn (50.4), Cu (7.56), I (0.77) Se (0.38). A completely randomized experimental design in a split-plot arrangement with 60 treatments of four replicates each was applied. The combination of six diets versus storage temperature (room or under refrigeration) was randomized in plots, whereas the sub-plots consisted of storage times (0...

Comparative Trace Elemental Analysis in Cancerous and Noncancerous Human Tissues Using PIXE

Mulware, Stephen Juma
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
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37.341116%
The effect of high or low levels of trace metals in human tissues has been studied widely. There have been detectable significant variations in the concentrations of trace metals in normal and cancerous tissues suggesting that these variations could be a causative factor to various cancers. Even though essential trace metals play an important role such as stabilizers, enzyme cofactors, elements of structure, and essential elements for normal hormonal functions, their imbalanced toxic effects contribute to the rate of the reactive oxygen species (ROS) and formation of complexities in the body cells which may lead to DNA damage. The induction of oxidative-induced DNA damage by ROS may lead to isolated base lesions or single-strand breaks, complex lesions like double-strand breaks, and some oxidative generated clustered DNA lesions (OCDLs) which are linked to cell apoptosis and mutagenesis. The difference in published works on the level of variations of trace metals in different cancer tissues can be attributed to the accuracy of the analytical techniques, sample preparation methods, and inability of taking uniform samples from the affected tissues. This paper reviews comparative trace elemental concentrations of cancerous and noncancerous tissues using PIXE that has been reported in the published literature.

Discovery and genetic analysis of non-bitter Tartary buckwheat (Fagopyrum tataricum Gaertn.) with trace-rutinosidase activity

Suzuki, Tatsuro; Morishita, Toshikazu; Mukasa, Yuji; Takigawa, Shigenobu; Yokota, Satoshi; Ishiguro, Koji; Noda, Takahiro
Fonte: Japanese Society of Breeding Publicador: Japanese Society of Breeding
Tipo: Artigo de Revista Científica
EN
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In a screening of about 500 lines of Tartary buckwheat, we identified lines that contained no detectable rutinosidase isozymes using an in-gel detection assay. We confirmed that seeds of these individuals had only a trace level of in-vitro rutinosidase activity. To investigate the heritability of the trace-rutinosidase characteristic, we analyzed the progeny of crosses between rutinosidase trace-lines, ‘f3g-162’, and the ‘Hokkai T8’. The F2 progeny clearly divided into two groups: those with rutinosidase activity under 1.5 nkat/g seed (trace-rutinosidase) and those with activity over 400 nkat/g seed (normal rutinosidase). The segregation pattern of this trait in F2 progeny exhibited 1 : 3 ratio (trace-rutinosidase : normal rutinosidase), suggesting that the trace-rutinosidase trait is conferred by a single recessive gene; rutinosidase-trace A (rutA). In addition, sensory panelists evaluated the bitterness of flour from trace-rutinosidase individuals and did not detect bitterness, whereas flour from normal rutinosidase individuals was found to have strong bitterness. Although at least three bitter compounds have been reported in Tartary buckwheat seeds, our present findings indicate that rutin hydrolysis is the major contributing factor to bitterness. In addition...

Simultaneous multi-laser, multi-species trace-level sensing of gas mixtures by rapidly swept continuous-wave cavity-ringdown spectroscopy

He, Y.; Kan, R.; Englich, F.; Liu, W.; Orr, B.
Fonte: Optical Soc Amer Publicador: Optical Soc Amer
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
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The greenhouse-gas molecules CO2, CH4, and H2O are detected in air within a few ms by a novel cavity-ringdown laser-absorption spectroscopy technique using a rapidly swept optical cavity and multi-wavelength coherent radiation from a set of pre-tuned near-infrared diode lasers. The performance of various types of tunable diode laser, on which this technique depends, is evaluated. Our instrument is both sensitive and compact, as needed for reliable environmental monitoring with high absolute accuracy to detect trace concentrations of greenhouse gases in outdoor air.; Yabai He, Ruifeng Kan, Florian V. Englich, Wenqing Liu and Brian J. Orr

State-trace analysis of associative recognition: comparing single-process and dual-process models.

Hamm, Nicholas
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2014
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The aim of this thesis is to investigate competing explanations of the processes underlying associative recognition. Like recognition memory for individual items, associative recognition is currently understood through two different classes of model. The first is the single-process model class which holds that associative recognition decisions are based on a continuum of associative memory strength. The second is the dual-process model class, which holds that associative recognition decisions are based on two sources of information, called familiarity and recollection. Familiarity is conceptualised as a fast-acting, context-free „feeling of knowing‟, while recollection is said to be a slower, more conscious process allowing for the recall of detail and context. Familiarity may play a role in associative recognition through a mechanism called unitisation, whereby two distinct stimuli are bound into a single individual memory trace. State-trace analysis is a method to determine the number of latent variables or processes that contribute to performance on a set of tasks, under mild assumptions. A critical diagnostic feature is the dimensionality of the state-trace plot – a plot of performance on one dependent variable against the other. If associative recognition depends on a single latent variable then manipulation of experimental factors affecting memory should result in a unidimensional state-trace plot. If associative recognition depends on two or more latent variables which are differentially affected by the experimental factors then a bidimensional state-trace will result. State-trace analysis therefore provides a method of discriminating a class of single-process models from a class of dual-process models. State-trace analysis was applied to associative recognition in four experiments. Each experiment utilised two independent variables that previous research had suggested could differentially affect familiarity and recollection. Experiment 1 investigated associative recognition of word pairs by manipulating attention and study presentation frequency. Experiments 2 investigated associative recognition of word pairs under conditions designed to encourage unitisation by pairing an encoding-based unitisation manipulation with a working memory load manipulation. Experiment 3 manipulated the same unitisation instructions as well as varying study time. Experiment 4 examined the effect of unitisation using pairs of faces and manipulated visual similarity and study time. State-trace analysis of the four experiments consistently revealed unidimensional state-trace plots. Using a recently developed monotonic regression statistical test...

Comparison of the relative comparator and k₀ neutron activation analysis techniques for the determination of trace-element concentrations in pyrite; Comparison of the relative comparator and k(0) neutron activation analysis techniques for the determination of trace-element concentrations in pyrite

Osborne, O.D.; Pring, A.; Popelka-Filcoff, R.S.; Bennett, J.W.; Stopic, A.; Glascock, M.D.; Lenehan, C.E.
Fonte: Mineralogical Society Publicador: Mineralogical Society
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
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47.54456%
Thirty pyrite samples from a wide range of localities were analysed using relative comparator and k0 neutron activation analysis (NAA) techniques at the University of Missouri Research Reactor, Columbia, Missouri, USA (MURR) and the Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia (ANSTO), respectively. Statistical analyses of the trace-element data produced by the two methods showed a generally good correlation, with the majority of elemental concentrations of paired data reported by MURR and ANSTO being indistinguishable at a 0.05 significance level. Trace-element analyses of pyrite from Navajun in Spain by both techniques compare well with published data. There is evidence for contamination by Al, Na and Ti in one set of samples, this is likely to have been introduced by contact with a plastic used in sample preparation.; O. D. Osborne, A. Pring, R. S. Popelka-Filcoff, J. W. Bennett, A. Stopic, M. D. Glascock, and C. E. Lenehan

Application of Bar Adsorptive Microextraction-Large-Volume Injection-Gas Chromatography-Mass Spectrometric Method for the Determination of Trace Levels of Agrochemicals in Real Matrices

Bernarda,João R.; Ahmad,Samir M.; Almeida,Carlos; Neng,Nuno R.; Nogueira,José Manuel F.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2015 EN
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Bar adsorptive microextraction followed by liquid desorption in combination with large volume injection gas chromatography coupled to mass spectrometry, under selected ion monitoring mode acquisition (BAµE-LD/LVI-GC-MS(SIM)), was applied for the determination of trace levels of different classes of agrochemicals (using alachlor, diniconazole, fenpropathrin, as well as cis and trans-permethrin as model compounds) in environmental water and wine matrices. Assays performed on 25 mL of ultra-pure water samples spiked at the 2.0 µg L-1 level, yielded recoveries ranging from 55.2 to 105.6%, under optimized experimental conditions. The analytical performance showed convenient detection limits (8.0 to 32.0 ng L-1) and good linear dynamic ranges (0.03 to 4.00 µg L-1), with remarkable determination coefficients (r2 > 0.9982). Excellent repeatability, based in relative standard deviation (RSD) was also achieved through intraday (RSD < 7.5%) and interday (RSD < 7.0%) assays. Studies performed on surface and ground water, as well as wine samples, using the standard addition method, revealed good sensitivity at the trace level.

The Review of Nuclear Microscopy Techniques: An Approach for Nondestructive Trace Elemental Analysis and Mapping of Biological Materials

Mulware, Stephen Juma
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
47.37244%
The properties of many biological materials often depend on the spatial distribution and concentration of the trace elements present in a matrix. Scientists have over the years tried various techniques including classical physical and chemical analyzing techniques each with relative level of accuracy. However, with the development of spatially sensitive submicron beams, the nuclear microprobe techniques using focused proton beams for the elemental analysis of biological materials have yielded significant success. In this paper, the basic principles of the commonly used microprobe techniques of STIM, RBS, and PIXE for trace elemental analysis are discussed. The details for sample preparation, the detection, and data collection and analysis are discussed. Finally, an application of the techniques to analysis of corn roots for elemental distribution and concentration is presented.

Development of a multi-residue analytical methodology based on liquid chromatography–tandem mass spectrometry (LC–MS/MS) for screening and trace level determination of pharmaceuticals in surface and wastewaters

Gros, Meritxell; Petrovic, Mira; Barceló, Damià
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 19968 bytes; application/msword
ENG
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46.86055%
13 pages, 5 tables, 6 figures.; This paper describes development, optimization and validation of a method for the simultaneous determination of 29 multi-class pharmaceuticals using off line solid phase extraction (SPE) followed by liquid chromatography–triple quadrupole mass spectrometry (LC–MS–MS). Target compounds include analgesics and non-steroidal anti-inflammatories (NSAIDs), lipid regulators, psychiatric drugs, anti-histaminics, anti-ulcer agent, antibiotics and β-blockers. Recoveries obtained were generally higher than 60% for both surface and wastewaters, with exception of several compounds that yielded lower, but still acceptable recoveries: ranitidine (50%), sotalol (50%), famotidine (50%) and mevastatin (34%). The overall variability of the method was below 15%, for all compounds and all tested matrices. Method detection limits (MDL) varied between 1 and 30 ng/L and from 3 to 160 ng/L for surface and wastewaters, respectively. The precision of the method, calculated as relative standard deviation (R.S.D.), ranged from 0.2 to 6% and from 1 to 11% for inter and intra-day analysis, respectively. A detailed study of matrix effects was performed in order to evaluate the suitability of different calibration approaches (matrix-matched external calibration...

In situ trace element analysis of macerals and minerals in coals using laser ablation ICP-MS

Spears, D. A.; Gómez Borrego, Ángeles; Cox, A.; Martínez Tarazona, M.ª Rosa
Fonte: Conselho Superior de Investigações Científicas Publicador: Conselho Superior de Investigações Científicas
Tipo: Comunicación de congreso Formato: 140298 bytes; application/pdf
ENG
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47.1188%
Laser ablation inductively coupled plasma-mass spectrometry (LA ICP-MS) offers the possibility of directly analysing individual, micron-sized coal components down to the ppm level using polished sections or blocks and therefore free from the need to separate components. A number of representative coals have been analysed for V, Ge, Ni, Cu, Zn, Sr and Ba, which were known to have some organic association. Aluminium and Fe were included as controls on the abundances of the clay and pyrite. Sporinite was found to have low trace element concentrations, inertinite higher concentrations of detrital elements and vitrinite higher concentrations of V, Ge and Al. It is thought that these latter elements became concentrated during diagenesis from circulating porewaters.; Peer reviewed

Trace Level Determination of Domoic Acid in Seawater by Off-line/on-line Solid-phase Extraction Coupled to HPLC-UV

Vera-Avila,Luz Elena; Marín-Pérez,Deny Y.; Covarrubias-Herrera,Rosario
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2011 EN
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46.75659%
Domoic acid (DA) is a marine neurotoxin mainly produced by microalgae of the genus Pseudo-nitzschia and is considered the main responsible for a human intoxication syndrome known as amnesic shellfish poisoning. In this work, a method for the determination of the biotoxin at low ppb or sub-ppb concentration levels in seawa-ter was developed based on a double solid-phase extraction (SPE) followed by on-line transfer and HPLC-UV analysis of the whole extract. First, preconcentration of DA from 100-mL sample volumes and convenient sample cleanup is achieved by off-line SPE on a reversed phase C18 cartridge. Then, the extract is diluted and loaded in a polymeric reversed phase precolumn, which is further on-line eluted and analyzed. A critical condition for retaining the hydrophilic analyte in the cartridge or the precolumn is the addition of acid and an ion pairing reagent to the loading solution. Recoveries exceeded 90% for all tested seawater samples spiked with DA at 0.5-1 ng/mL. Good precision (<5%) and a limit of detection of 0.04 ng/mL were obtained with this simple method that only requires the use of conventional instrumentation existing in most analytical laboratories in Mexico.

On-line methodology for the trace level determination of the chlorinated phenol family in water samples

Núñez-Gaytán,Ana María; Vera-Ávila,Luz Elena; Covarrubias-Herrera,María del Rosario
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2008 EN
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57.246387%
On-line solid-phase extraction - liquid chromatography (SPE-HPLC) methodology was developed for the trace level determination of phenol and 19 chlorophenols in water samples. A small precolumn packed with polymeric adsorbent was placed in a switching valve and used for sample extraction and preconcentration; the trapped compounds were further on-line eluted and analyzed by reversed phase HPLC with UV and coulometric detection. Because of wide differences in hydrophobic character, SPE of the least (phenol and monochlophenols), the medium (di- and trichlorophenols) and the most chlorinated phenols (tetra- and pentachlorophenol) was performed using different sample volume (15-25 mL) and sample composition (0-10% methanol addition). Under these conditions, solute recoveries were ≥ 82% (except phenol, 72%) for concentrations in the range ~3-75 ng/mL. Applying recovery factors, excellent accuracy (100%) and precision (RSD < 6.5%) were achieved for the 20 compounds of interest in replicate analysis (n = 7) of spiked reagent water samples. Method detection limits were 0.5-1 ng/mL with the UV detector and 0.1-0.3 ng/mL with the coulometric detector.

Trace metal analysis in sea grasses from Mexican Caribbean Coast by particle induced X-ray emission (PIXE)

Solís,C; Martínez,A; Lavoisier,E; Martínez,M.A; Isaac-Olivé,K
Fonte: Sociedad Mexicana de Física Publicador: Sociedad Mexicana de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2008 EN
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47.47813%
The growing urban and tourist activity in the Mexican Caribbean coasts has resulted in an increase of chemical substances, metals in particular, discharged to the coastal waters. In order to reach an adequate management and conservation of these marine ecosystems it is necessary to perform an inventory of the actual conditions that reflect the vulnerability and the level of damage. Sea-grasses are considered good biological indicators of heavy metal contamination in marine systems. The goal of this preliminary work is to evaluate the concentrations of trace metals such as Cr, Mn, Fe, Co, Cu, Zn, and Pb in Thalassia testudinum, a very common sea-grass in the Mexican Caribbean Sea. Samples were collected from several locations in the coasts of the Yucatan Peninsula: Holbox, Blanquizal and Punta Allen, areas virtually uninfluenced by anthropogenic activities. Trace elements in different part plants were determined by particle induced X-ray emission (PIXE). This is a very suitable technique since it offers a fast, accurate and multi-element analysis. Also, the analysis by PIXE can be performed directly on powdered leaves without a laborious sample preparation. The trace metal concentration determined in sea-grasses growing in Caribbean generally fall in the range of the lowest valuables reported for sea grasses from the Gulf of México. The results indicate that the studied areas do not present contamination by heavy metals.

A Rapid Method for Measurement of Nickel and Chromium at Trace Level in Aqueous Samples

Salman,Muhammad; Shafique,Umer; Zaman,Waheed-uz; Rehman,Rabia; Yousaf,Amna; Azhar,Faiza; Anzano,Jesús M.
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2011 EN
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47.123525%
A rapid, simple and portable technique to measure Ni(II) and Cr(VI) at trace level in aqueous samples has been proposed. Colored spots were developed by interacting micro-liter drops of metal solutions with suitable reagents on TLC plates. Soon after, TLC having spots was scanned to import the image into the computer. Color densities of spots were calculated with the help of homemade software. Simple regression was practiced on calibration between standards' concentrations and their color densities. For both metals, correlation coefficients were approaching to one, which pointed out a good correlation between color densities and corresponding analyte concentrations. Real samples from electroplating unit were analyzed with the present and conventional spectrophotometric method (employed as reference), and the results were compared to evaluate the pertinence of the proposed technique in the real analysis.