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noneHsiao, Po-kai 20 July 2010 (has links)
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Identification and Quantification of selenium-containing compound in dietary supplement and arsenic-containing compound in seaweed by HPLC-ICP-MS and HPLC-ESI-MSHsieh, Yu-Jhe 20 July 2011 (has links)
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Determination of Selenium Compounds in Dietary Supplements and Foods Using Ion-pair Reversed-phase and Anion-exchange Chromatography ICP-MS and ESI-MSLin, Yi-Chun 22 July 2012 (has links)
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noneHuang, Sue-Jean 18 July 2000 (has links)
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noneLu, Hsin-Hsin 18 July 2000 (has links)
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Determination of chromium in water sample by inductively coupled plasma dynamic reavtion cell mass spectrometryChang, Yu-Ling 10 July 2001 (has links)
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noneChen, Kuei-Lan 10 July 2001 (has links)
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Study of pre-evaporation and matrix effects on multi-elemental analysis by ICP-TOFMSLiu, Shulan 19 July 2007 (has links)
The ultimate goal of this project was to improve the sensitivity and detection limits of inductively coupled plasma time-of-flight mass spectrometry (ICP-TOFMS) and then apply it to the speciation analysis of As. To this end, two approaches were taken: the use of organic modifiers and that of a pre-evaporation interface between the spray chamber and the plasma torch.
The radial profiles of some background ions and analytes in three different matrices (1% HNO3, 1% HNO3 with 2% v/v methanol, 1% HNO3 with 0.2% m/v sodium dodecylsulfate (SDS)) were investigated in ICP-TOFMS. Although these concentrations of methanol and SDS induced the same increase (37%) in sample introduction efficiency, the change in analyte signal as a function of m/z followed opposite trends in these two matrices. The results show that matrix effects arising from different organic modifiers affected the distribution of ions in the plasma differently as a result of changes induced in the predominant ionisation mechanisms in the plasma.
The effect of a pre-evaporation interface on the distribution of ions in ICP-TOFMS was also investigated by spatial profiling, which showed that the optimal axial position of all elements shifted closer to the load coil. Furthermore, the radial profiles became significantly narrower and Gaussian. The decrease of droplet size thus improved the sensitivity and detection limits for multi-elemental analysis.
A further investigation of the effect of the pre-evaporation interface revealed that, for cationic analytes, the signal enhancement had an inverse dependency on analyte mass upon heating the interface. In the case of As, a signal enhancement upon heating the interface only resulted when concomitant ionic analytes were present or with a 0.01 M NaOH matrix. All these observations could be rationalised by changes in the number of Coulomb fission events occurring during pre-evaporation, which depend on the size and charge of droplets, as well as the identity and concentration of the matrix.
Finally, the baseline separation of four As species by ion exchange liquid chromatography with detection by ICP-TOFMS and application of the pre-evaporation interface tube to As speciation were achieved using a mobile phase of NH4NO3, following an investigation of its matrix effects. / Thesis (Ph.D, Chemistry) -- Queen's University, 2007-07-12 13:51:55.115
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[en] METHOD DEVELOPMENT FOR THE DETERMINATION OF TOTAL SE BY ICP-MS AND ITS SPECIES BY HPLC-ICP-MS IN FOOD SUPPLEMENT AND IN ISOTOPICALLY ENRICHED YEAST / [pt] DESENVOLVIMENTO DE MÉTODOS PARA DETERMINAÇÃO DE SE TOTAL POR ICP-MS E DE SUAS ESPÉCIES POR HPLC-ICP-MS EM SUPLEMENTO ALIMENTAR E LEVEDURA ENRIQUECIDA ISOTOPICAMENTEJEFFERSON RODRIGUES DE SOUZA 27 April 2018 (has links)
[pt] O consumo de suplementos alimentares tem apresentado um aumento significativo nos últimos anos principalmente pelo grande apelo desse produto em relação a complementação da dieta com elementos essenciais e a melhora e manutenção da saúde. A combinação do crescente consumo e o livre acesso a esse produto, aliado a ausência de fiscalização por parte dos órgãos governamentais torna seu consumo descontrolado, um potencial risco a saúde da população. Nesse cenário o desenvolvimento de métodos analíticos destinados ao controle de qualidade incluindo a determinação da concentração de selênio total e de suas espécies torna-se uma necessidade. Para isso, foram desenvolvidas metodologias para a quantificação de selênio total por ICP-MS e suas espécies inorgânicas (Se IV e Se VI) e selenometionina por HPLC-ICP-MS em amostras de suplementos alimentares enriquecidos em selênio e em amostra de levedura enriquecida isotopicamente em 78Se. A metodologia para determinação de selênio total, utilizando diferentes gases de reação, foi otimizada empregando planejamento experimental e os limites de detecção encontrados foram entre 0,01 mg kg(-1) (CH4) e 0,1 mg kg(-1) (NH3) e a concordância com o MRC Selm-1 de entre 99 por cento (NH3) e 104 por cento (CH4). Os resultados encontrados referentes à concentração de selênio nas amostras de suplementos alimentares apresentaram uma discrepância em relação ao valor informado no rótulo entre -29 por cento e +170 por cento e, de maneira complementar, o acoplamento do HPLC ao ICP-MS permitiu realizar a especiação de selênio nas amostras de suplemento alimentar. O emprego das técnicas ICP-MS, HPLC-ICP-MS e ESI-MS possibilitou a caracterização de uma amostra de levedura enriquecida isotopicamente em 78Se em termos de sua distribuição isotópica, concentração de selênio total e selenometionina bem como proteínas com peso molecular de aproximadamente 12 kDa. / [en] The consumption of dietary supplements has a significant increase in recent years mainly for a great appeal of this product in relation to a complementation of the diet with essential elements and an improvement and maintenance of health. The combination of increased consumption and free access to this product, associated to the lack in the inspection by government, makes their consumption uncontrolled and a potential risk to the citizen health. In this scenario the development of analytical methods for quality control, including a determination of the total selenium concentration and its species becomes a primordial necessity. For this, methodologies were developed for quantification of total selenium by ICP-MS and its inorganic species (Se IV and Se VI) and selenomethionine by HPLC-ICP-MS in samples of selenium-based food supplements and in isotopically enriched yeast sample in 78Se. The methodology for total selenium determination was optimized by experimental design and the limits of detection were in the range of 0.01 mg kg(-1) (CH4) and 0.1 mg kg(-1) (NH3) and the agreement with the CRM Selm-1 were between 99 percent (NH3) and 104 percent (CH4). The results found for selenium content in the food supplements samples presented a discrepancy in relation to the labeled value between -29 percent and + 170 percent and, complementarily, coupling of HPLC to ICP-MS allowed an speciation analysis in the food supplements samples. The use of the ICP-MS, HPLC-ICP-MS and ESI-MS techniques enabled a characterization of a 78Se isotopically enriched yeast sample in terms of its isotopic distribution, total selenium concentration and selenomethionine as well as proteins with molecular weight of approximately 12 kDa.
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Estudo dos Teores de Pb, Cd, Sn, Co, V, Hg, Mo e As em Sedimentos e Fungos Liquenizados, da Ilha Rei George, Península Fildes - Antártica Utilizando a Técnica de Icp-msDALFIOR, B. M. 16 November 2015 (has links)
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Previous issue date: 2015-11-16 / O continente Antártico é um dos poucos lugares que não foi explorado em sua totalidade, porém estudos revelam que esse local está sofrendo interferência pelas atividades antrópicas. Por esse motivo, o monitoramento desta região torna-se muito importante. Após otimização e verificação da metodologia as concentrações biodisponíveis nas amostras de sedimento coletadas ao longo de toda a Península Fildes, Ilha Rei George, Antártica, foram determinadas por ICP-MS. As faixas encontradas em µg kg-1 foram 525,17 2314,11 (Pb), 54,83 193,77 (Cd), 54,83 193,77 (Sn), 2095,04 11094,1 (Co), < 2,4 54,61 (Hg), < 5,3 38,66 (Mo) e 120,31 1297,06 (As). Quando comparados esses valores com os descritos na literatura verifica-se que estão abaixo ou dentro da faixa já reportada. A presença desses elementos nas amostras pode ser atribuída à diferentes fatores, tais como a composição natural do sedimento, a contaminação por estações científicas, a existência de uma pista de pouso local, além do transporte local e global de elementos químicos causados pelos fenômenos físicos, o que acarretaria a deposição dos mesmos em diferentes matrizes.
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