The objective of the present work was systematic investigation of water-based headspace single-drop microextraction (SDME) technique, its conjunction with capillary electrophoresis, and application for the analysis of volatile inorganic compounds (cyanide and ammonium) in biomedical and environmental samples. Theoretically evaluated and experimentally confirmed that the manipulation in the volatility of the analyte by its chemical modification in the sample and/or in the acceptor phase is the most effective way to enhance the extraction performance in headspace SDME. Maximum extraction efficiency for cyanide was observed in the pH range 4.5–7.5, where cyanide anion is completely transferred into volatile HCN. Complete cyanide recoveries (≥96%) from metal-cyanide complexes were obtained by using two ligand-exchange reagents (ethylenediamine and dithizone). Maximum extraction efficiency was observed by the extraction of ammonia from alkaline samples (pH≥11) with neutral or slightly acidic acceptor phase (pH 3-7). Compared to existing methods water-based headspace SDME is significantly faster and simpler. In addition, proposed technique does not require any sample pre-treatment (deproteinization, acidic/alkaline distillation, etc.) and thus is much less susceptible to interferences. Finally, it offers possibility to choice of a wider variety of solvents and, consequently, enhances the range of extractable analytes as well as the range of analytical methods that can be coupled... [to full text] / Daktaro disertacijoje nuodugniai ištirtas mikroekstrakcijos iš viršerdvės vandens lašu metodas, apjungtas su kapiliarine elektroforeze bei pritaikytas lakių neorganinių junginių (cianido ir amonio) koncentravimui ir nustatymui biomedicininiuose ir aplinkos objektuose. Teoriniais skaičiavimais parodyta ir eksperimentiškai patvirtinta, kad efektyviausias būdas mikroekstrakcijos iš viršerdvės efektyvumui pagerinti – analitės lakumo didinimas chemiškai modifikuojant ją prieš ekstrakciją ir/arba jos lakumo mažinimas modifikuojant ją akceptorinėje fazėje. Maksimalus cianido mikroekstrakcijos efektyvumas pasiekiamas pH srityje 4,5- 7,5, kur cianidas kiekybiškai pervedamas į lakų HCN. Ištyrus cianido mikroekstrakciją tirpiklio lašu iš metalų cianidinių kompleksų tirpalų nustatyta, kad kiekybiškas silpnai surišto cianido suardymas (cianido išgavos siekia ≥96%) pasiekiamas panaudojus ligandų mainus etilendiamino ir ditizono mišiniu. Maksimalus amonio mikroekstrakcijos efektyvumas pasiekiamas ekstrahuojant jį iš pašarmintų mėginių (pH≥11) akceptorine faze, kurios pH 3-7. Lyginant su standartiniais metodais, siūlomas metodas yra greitesnis ir paprastesnis, visiškai eliminuojama mėginio matricos įtaka, nereikalingos jokios drastiškos (deproteinizacija, veikimas rūgštimis/šarmais, distiliacija ir pan.) manipuliacijos su mėginiu, todėl išvengiama mėginio matricos įtakos. Mikroekstrakcija iš viršerdvės vandens lašu praplečia mikroekstrakcijos metodų taikymo sritis: atveriama galimybė labai... [toliau žr. visą tekstą]

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2016-08-31T15:22:10Z No. of bitstreams: 1 VERSÃO FINAL DA DISSERTAÇÃO DE MESTRADO - RAFAEL DOURADO PIMENTA FONTES.pdf: 2834377 bytes, checksum: 4df31943280d22c5475b7e744e8d6683 (MD5) / Approved for entry into archive by Vanessa Reis (vanessa.jamile@ufba.br) on 2016-09-02T16:18:17Z (GMT) No. of bitstreams: 1 VERSÃO FINAL DA DISSERTAÇÃO DE MESTRADO - RAFAEL DOURADO PIMENTA FONTES.pdf: 2834377 bytes, checksum: 4df31943280d22c5475b7e744e8d6683 (MD5) / Made available in DSpace on 2016-09-02T16:18:17Z (GMT). No. of bitstreams: 1 VERSÃO FINAL DA DISSERTAÇÃO DE MESTRADO - RAFAEL DOURADO PIMENTA FONTES.pdf: 2834377 bytes, checksum: 4df31943280d22c5475b7e744e8d6683 (MD5) / CNPq e FAPESB / Na atualidade, o consumo de organismos marinhos (principalmente peixes e camarões) tem aumentado cada vez mais, devido à sua constituição proteica. Nos últimos anos, com a elevada demanda de pescados, intensificou-se também o cultivo (aquicultura), principalmente de camarão, para suprir o mercado consumidor. A aceitação de alimentos de origem marinha pelo consumidor está diretamente relacionada ao odor e sabor que devem ser atrativos e agradáveis. As principais substâncias químicas identificadas com as responsáveis pelo “flavor” dos alimentos marinhos são os bromofenóis simples 2-bromofenol (2-BF), 4-bromofenol (4-BF), 2,4-dibromofenol (2,4-DBF), 2,6-dibromofenol (2,6-DBF) e 2,4,6-tribromofenol (2,4,6-TBF). A microextração com gota única (SDME) é uma técnica que apresenta muitas vantagens, quando comparada com as técnicas clássicas, pois permite o isolamento e pré-concentração dos analitos em um passo único, seguida de introdução da amostra em sistema de análise por CG-EM. Esta técnica vem ganhando destaque por não ser exaustiva, utilizar uma quantidade muito pequena de solvente (estando de acordo com os preceitos da química verde), requer um curto tempo de análise, tem elevada sensibilidade e baixo custo. Nesse trabalho foi desenvolvida uma nova metodologia analítica baseada em SDME e CG-EM para determinação de bromofenóis em abdômen e ração de camarão cultivado (carcinicultura) (Lithopenaeus vannamei) e abdômen de camarão pescado (Xiphopenaeus kroyeri, camarão sete barbas) em diferentes estações do ano. A otimização da técnica por CG-EM permitiu boa separação dos bromofenóis simples em apenas 15 minutos. Esta nova metodologia foi validada em função da linearidade das curvas analíticas, limite de detecção e quantificação, precisão e recuperação para cada um dos cinco analitos estudados. A recuperação e precisão variaram, respectivamente, de 50,8 a 103% e de 2,27 a 18,8%. Os limites de detecção e quantificação variaram, respectivamente, de 0,200 a 0,499 ng mL-1 e de 0,500 a 1,000 ng mL-1. Não foi perceptível uma relação regular ou linear entre a sazonalidade e a concentração dos bromofenóis nos camarões pescados. Tanto na primavera quanto no verão a maior concentração detectada foi do 2,4-DBF, enquanto no outono e inverno foram o 4-BF e o 2-BF respectivamente. Já no abdômen do camarão de cativeiro e na ração deste a maior concentração foi do 4-BF. A menor concentração na ração, no abdômen do camarão cultivado e na estação verão corresponde ao 2-BF, na primavera e no outono ao 2,6-DBF, enquanto no inverno ao 4-BF. A metodologia desenvolvida, além de apresentar baixos limites de detecção e quantificação, envolve menor tempo de análise, menor consumo de energia e solventes, sendo assim compatível com os preceitos da Química Verde. / At present, the consumption of marine organisms (mainly fish and shrimp) has increased even more, due to its constitution protein. In recent years, with the high demand of fish, also accelerated cultivation (aquaculture), especially shrimp, to supply the consumer market. Acceptance of marine foods by consumers is directly related to odor and flavor that should be attractive and pleasant. The main chemicals identified as responsible for the "flavor" of marine foods are simple bromophenol 2-bromophenol (2-BF), 4-bromophenol (4-BF), 2,4-dibromophenol (2,4-DBF) 2,6-dibromophenol (2,6-DBF) and 2,4,6-tribromophenol (2,4,6-TBF). A single droplet with microextraction (SDME) is a technique that has many advantages compared with conventional techniques, since it allows the isolation and preconcentration of analytes in a single step, followed by introduction of the sample analysis system GC-MS. This technique has been gaining attention for not being exhaustive, use a very small amount of solvent (which is consistent with the principles of green chemistry), requires a short analysis time, has high sensitivity and low cost. In this work we developed a new analytical methodology based SDME and GC-MS to determine bromophenols in abdomen and feed farmed shrimp (Lithopenaeus vannamei) shrimp fished and abdomen (Xiphopenaeus kroyeri, seven shrimp whiskers) in different seasons year. Optimization of GC-MS technique allowed good separation of bromophenols simple in just 15 minutes. This new methodology was validated on the basis of the calibration curves linearity, limit of detection and quantification accuracy and recovery for each of the five analytes studied. The recovery and precision ranging, respectively, from 50,8 to 103% and from 2,27 to 18,8%. The limits of detection and quantification varied, respectively, from 0,200 to 0,499 ng ml-1 and 0,500 to 1,000 ng ml-1. It was not noticeable or a regular relationship between the linear and the concentration of bromophenol seasonality in shrimp fished. Both in spring and in summer the highest concentration detected was 2,4-DBF, while in autumn and winter were the 4-BF and 2-BF respectively. Already in the abdomen of shrimp feed in captivity and this was the highest concentration of 4-BF. The lowest concentration in the feed, abdomen farmed shrimp and summer season match 2-BF, in spring and autumn to 2,6-DBF, while in winter the 4-BF. The methodology developed, and have low limits of detection and quantification, involves less analysis time, lower power consumption and solvents and is therefore compatible with the principles of Green Chemistry

Parabens are effective antibacterial and anti-fungal agents and are used extensively as preservatives in cosmetics, food and pharmaceutical products. Because of the presence of parabens in the environment and their negative effects on human health, there is an increasing interest in their trace analysis. Since the concentration of parabens in the environment are rather low and cosmetics present rather complex matrices for the analysis, it is necessary to apply a preconcentration or isolation step prior to the chromatographic analysis. The aim of this work was to develop liquid-phase microextraction methods – single drop microextraction, hollow fibre liquid phase microextraction and dispersive liquid-liquid microextraction – for parabens and to apply the methods for determination of parabens in water samples and cosmetic products. Extraction conditions for single drop microextraction, hollow fibre liquid phase microextraction and dispersive liquid-liquid microextraction were optimized and the quality parameters of the suggested methods were calculated. The influence of derivatization on the paraben extraction efficiency was evaluated. Prepared microextraction methods were applied for the determination of parabens in real samples. / Parabenai pasižymi antibakterinėmis bei priešgrybelinėmis savybėmis ir plačiai naudojami kosmetikos, maisto, farmacijos pramonėje kaip konservantai, apsaugantys produktus nuo ankstyvo gedimo ir prailginantys jų galiojimo laiką. Padidėjus įtarimams, jog prasiskverbę per odą parabenai gali sukelti alergines reakcijas, ardyti endokrininę sistemą, skatinti vėžinių ląstelių gamybą, buvo pradėta kontroliuoti jų kiekį aplinkoje, maisto bei kosmetikos produktuose. Tačiau parabenų koncentracijos dažnai yra per mažos, o mėginiai per daug sudėtingi, kad juos būtų galima analizuoti nesukoncentravus ir neizoliavus nuo trukdančios matricos. Šioje daktaro disertacijoje apibendrintų mokslinių tyrimų tikslas – sukurti parabenų skysčių-skysčių mikroekstrakcijos metodus – mikroekstrakciją tirpiklio lašu, skystafazę mikroekstrakciją kapiliare ir dispersinę skysčių-skysčių mikroekstrakciją – bei pritaikyti juos parabenų nustatymui vandenyje bei kosmetikos produktuose. Optimizuotos mikroekstrakcijos tirpiklio lašu, skystafazės mikroekstrakcijos kapiliare ir dispersinės skysčių-skysčių mikroekstrakcijos ekstrakcijos sąlygos ir nustatytos pagrindinės analizinės charakteristikos. Ištirta parabenų derivatizacijos įtaka parabenų dujų chromatografinio nustatymo efektyvumui. Paruošti parabenų mikroekstrakcijos metodai pritaikyti vandens ir kosmetikos mėginių analizei.

Parabenai pasižymi antibakterinėmis bei priešgrybelinėmis savybėmis ir plačiai naudojami kosmetikos, maisto, farmacijos pramonėje kaip konservantai, apsaugantys produktus nuo ankstyvo gedimo ir prailginantys jų galiojimo laiką. Padidėjus įtarimams, jog prasiskverbę per odą parabenai gali sukelti alergines reakcijas, ardyti endokrininę sistemą, skatinti vėžinių ląstelių gamybą, buvo pradėta kontroliuoti jų kiekį aplinkoje, maisto bei kosmetikos produktuose. Tačiau parabenų koncentracijos dažnai yra per mažos, o mėginiai per daug sudėtingi, kad juos būtų galima analizuoti nesukoncentravus ir neizoliavus nuo trukdančios matricos. Šioje daktaro disertacijoje apibendrintų mokslinių tyrimų tikslas – sukurti parabenų skysčių-skysčių mikroekstrakcijos metodus – mikroekstrakciją tirpiklio lašu, skystafazę mikroekstrakciją kapiliare ir dispersinę skysčių-skysčių mikroekstrakciją – bei pritaikyti juos parabenų nustatymui vandenyje bei kosmetikos produktuose. Optimizuotos mikroekstrakcijos tirpiklio lašu, skystafazės mikroekstrakcijos kapiliare ir dispersinės skysčių-skysčių mikroekstrakcijos ekstrakcijos sąlygos ir nustatytos pagrindinės analizinės charakteristikos. Ištirta parabenų derivatizacijos įtaka parabenų dujų chromatografinio nustatymo efektyvumui. Paruošti parabenų mikroekstrakcijos metodai pritaikyti vandens ir kosmetikos mėginių analizei. / Parabens are effective antibacterial and anti-fungal agents and are used extensively as preservatives in cosmetics, food and pharmaceutical products. Because of the presence of parabens in the environment and their negative effects on human health, there is an increasing interest in their trace analysis. Since the concentration of parabens in the environment are rather low and cosmetics present rather complex matrices for the analysis, it is necessary to apply a preconcentration or isolation step prior to the chromatographic analysis. The aim of this work was to develop liquid-phase microextraction methods – single drop microextraction, hollow fibre liquid phase microextraction and dispersive liquid-liquid microextraction – for parabens and to apply the methods for determination of parabens in water samples and cosmetic products. Extraction conditions for single drop microextraction, hollow fibre liquid phase microextraction and dispersive liquid-liquid microextraction were optimized and the quality parameters of the suggested methods were calculated. The influence of derivatization on the paraben extraction efficiency was evaluated. Prepared microextraction methods were applied for the determination of parabens in real samples.