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      Determination of vanadium in urine by electrothermal atomic absorption spectrometry using hot injection and preconcentration into the graphite tube

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          Abstract

          In this work it was developed a procedure for the determination of vanadium in urine samples by electrothermal atomic absorption spectrometry using successive injections for preconcentration into a preheated graphite tube. Three 60 µL volumes were sequentially injected into the atomizer preheated to a temperature of 110 ºC. Drying and pyrolysis steps were carried out after each injection. A chemical modifier, barium difluoride (100 mg L-1), and a surfactant, Triton X-100 (0.3% v v-1), were added to the urine sample. When injecting into a hot graphite tube, the sample flow-rate was 0.5 µL s-1. The limits of detection and quantification were 0.54 and 1.82 without preconcentration, and 0.11 and 0.37 µg L-1 with preconcentration, respectively. The accuracy of the procedure was evaluated by an addition-recovery experiment employing urine samples. Recoveries varied from 96.0 to 103% for additions ranging from 0.8 to 3.5 µg L-1 V. The developed procedure allows the determination of vanadium in urine without any sample pretreatment and with minimal dilution of the sample.

          Translated abstract

          É proposto um procedimento para a determinação direta de vanádio em amostras de urina por espectrometria de absorção atômica com atomização eletrotérmica em forno de grafite usando injeção à quente e pré-concentração dentro do tubo de grafite. Três aliquotas de 60 µL foram injetados seqüencialmente dentro do atomizador pré-aquecido a uma temperatura de 110 ºC. As etapas de secagem e pirólise foram repetidas após cada injeção. Às amostras de urina foram adicionados o modificador químico fluoreto de bário (100 mg L-1) e o surfactante Triton X-100 (0,3% v v-1). A vazão da amostra durante a injeção dentro do tubo pré-aquecido foi de 0,5 µL s-1. Os limites de detecção e de quantificação sem pré-concentração foram, respectivamente, 0,54 e 1,82 mg L-1, e com pré-concentração 0,11 e 0,37 µg L-1. O teste de adição e recuperação foi empregado em amostras de urina para avaliar a exatidão do procedimento proposto. Os valores de recuperação obtidos variaram de 96,0 a 103,0% para as adições de 0,8 a 3,5 µg L-1 V. O procedimento proposto possibilita a determinação de vanádio sem nenhum pré-tratamento e com mínima diluição da amostra.

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          Most cited references7

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          Identification of chemical inhibitors of protein-kinase CK2 subunit interaction.

          Protein kinase CK2 is a multi-subunit complex whose dynamic assembly appears as a crucial point of regulation. The ability to interfere with specific protein-protein interactions has already provided powerful means of influencing the functions of selected proteins within the cell. CK2beta-derived cyclopeptides that target a well-defined hydrophobic pocket on CK2alpha have been previously characterized as potent inhibitors of CK2 subunit assembly [9]. As a first step toward the rational design of low molecular weight CK2 antagonists, we have in the present study screened a collection of podophyllotoxine indolo-analogues to identify chemical inhibitors of the CK2 subunit interaction. We report the identification of a podophyllotoxine indolo-analogue as a chemical ligand that binds to the CK2alpha/CK2beta interface inducing selective disruption of the CK2alpha/CK2beta assembly and concomitant inhibition of CK2alpha activity.
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            Development and exploitation of CK2 inhibitors.

            A number of quite specific and fairly potent inhibitors of protein kinase CK2, belonging to the classes of condensed polyphenolic compounds, tetrabromobenzimidazole/triazole derivatives and indoloquinazolines are available to date. The structural basis for their selectivity is provided by a hydrophobic pocket adjacent to the ATP/GTP binding site, which in CK2 is smaller than in the majority of other protein kinases due to the presence of a number of residues whose bulky side chains are generally replaced by smaller ones. Consequently a doubly substituted CK2 mutant V66A,I174A is much less sensitive than CK2 wild type to these classes of inhibitors. The most efficient inhibitors both in terms of potency and selectivity are 4,5,6,7-tetrabromo-1H-benzotriazole, TBB (Ki = 0.4 microM), the TBB derivative 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole, DMAT (Ki = 0.040 microM), the emodin related coumarinic compound 8-hydroxy-4-methyl-9-nitrobenzo[g]chromen-2-one, NBC (Ki = 0.22 microM) and the indoloquinazoline derivative ([5-oxo-5,6-dihydroindolo-(1,2a)quinazolin-7-yl]acetic acid), IQA (Ki = 0.17 microM). These inhibitors are cell permeable as judged from ability to block CK2 in living cells and they have been successfully employed, either alone or in combination with CK2 mutants refractory to inhibition, to dissect signaling pathways affected by CK2 and to identify the endogenous substrates of this pleitropic kinase. By blocking CK2 these inhibitors display a remarkable pro-apoptotic efficacy on a number of tumor derived cell lines, a property which can be exploited in perspective to develop antineoplastic drugs.
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              Troponin I: inhibitor or facilitator.

              TN-I occurs as a homologous group of proteins which form part of the regulatory system of vertebrate and invertebrate striated muscle. These proteins are present in vertebrate muscle as isoforms, Mr 21000-24000, that are specific for the muscle type and under individual genetic control. TN-I occupies a central position in the chain of events starting with the binding of calcium to troponin C and ending with activation of the Ca2+ stimulated MgATPase of the actomyosin filament in muscle. The ability of TN-I to inhibit the MgATPase of actomyosin in a manner that is accentuated by tropomyosin is fundamental to its role but the molecular mechanism involved is not yet completely understood. For the actomyosinATPase to be regulated the interaction of TN-I with actin, TN-C and TN-T must undergo changes as the calcium concentration in the muscle cell rises, which result in the loss of its inhibitory activity. A variety of techniques have enabled the sites of interaction to be defined in terms of regions of the polypeptide chain that must be intact to preserve the biological properties of TN-I. There is also evidence for conformational changes that occur when the complex with TN-C binds calcium. Nevertheless a detailed high resolution structure of the troponin complex and its relation to actin/tropomyosin is not yet available. TN-I induces changes in those proteins with which it interacts, that are essential for their function. In the special case of cardiac TN-I its effect on the calcium binding properties of TN-C is modulated by phosphorylation. It has yet to be determined whether TN-I acts directly as an inhibitor or indirectly by interacting with associated proteins to facilitate their role in the regulatory system.
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                Author and article information

                Journal
                jbchs
                Journal of the Brazilian Chemical Society
                J. Braz. Chem. Soc.
                Sociedade Brasileira de Química (São Paulo, SP, Brazil )
                0103-5053
                1678-4790
                October 2004
                : 15
                : 5
                : 676-681
                Affiliations
                [03] Araraquara SP orgnameUniversidade Estadual Paulista orgdiv1Instituto de Química Brazil
                [02] São Carlos SP orgnameEmbrapa Pecuária Sudeste Brazil
                [01] São Carlos SP orgnameUniversidade Federal de São Carlos orgdiv1Departamento de Química Brazil
                Article
                S0103-50532004000500011 S0103-5053(04)01500511
                10.1590/S0103-50532004000500011
                0eba5164-3938-4b37-8bcb-4e7b6deece1f

                This work is licensed under a Creative Commons Attribution 4.0 International License.

                History
                : 17 August 2004
                : 28 October 2003
                Page count
                Figures: 0, Tables: 0, Equations: 0, References: 24, Pages: 6
                Product

                SciELO Brazil

                Self URI: Full text available only in PDF format (EN)
                Categories
                Articles

                ETAAS,preconcentration,hot injection,vanadium,urine
                ETAAS, preconcentration, hot injection, vanadium, urine

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