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Electrochemical Remedy and Analysis for the Environment Based on the New Polymer-DNA Composite Material.Hussain, Noor Feuza 16 August 2005 (has links)
In this work a new material, the conducting polymer-DNA composite, has been reported for the first time due to its promise in micro extraction, transfer, and release of cations under controlled potential conditions by using electrochemically assisted solid phase micro extraction (SPME). The Polypyrrole/DNA composite can be formed easily by oxidation of pyrrole monomers in the presence of chromosomal DNA by electropolymerization. Environmental significant pollutants such as Cd, Pb, Hg, Co, Zn, Cu, and Bi metal ions can be extracted from the aqueous solution and are able to be transferred to another medium defined as the release solution where the metals were detected by anodic stripping voltammetry. Using Cd2+ as a model, this method has been examined to optimize its operational condition. Extraction efficiency and potential interference for this method were studied.
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Lead (Pb) Contamination of Water Drawn from Pitcher Pumps in Eastern MadagascarAkers, David Bradlee 25 March 2014 (has links)
Access to safe water supply--a major determinant of public health--is less than 50% in Madagascar, and access to piped, treated water remains out of reach financially for many in the urban and peri-urban areas where available. The Self-supply option of the Pitcher Pump has been meeting the need for household water in coastal areas of Madagascar since the early 1960s and has proven a sustainable option for many. These pumps make use of leaded components in the construction, however, which may pose a health risk for heavy metal intoxication and therefore cause the water to be unsafe for drinking and cooking. This study assesses the potential for lead (Pb) leaching from Pitcher Pump systems into water at levels of health concern. The objectives of this study are to assess Pb concentrations in water drawn from Pitcher Pumps, to determine the relationship between various factors and the Pb levels, to make a preliminary assessment of public health implications of Pb contamination, and to offer informed recommendations to reduce the likelihood of consuming contaminated water.
A field study was undertaken to measure concentrations of dissolved Pb in water from Pitcher Pumps under recently flushed and first-draw pumping conditions at 18 households in the city of Tamatave, Madagascar. Variables potentially affecting Pb leaching were determined including pump age, depth to the well screen, pump manufacturer, season of sample collection, and basic water quality indicators. Sampling campaigns were conducted three times over the course of eight months. Time-release case studies were also carried out at two households to determine the time scale over which the Pb concentration in stationary water reaches equilibrium with the Pb-containing system components. Pilot studies of iron (Fe)-for-Pb substitution of select pump system components were carried out at the same two households to attribute the major contribution of Pb leaching to one set of parts and to assess one strategy for decreasing dissolved Pb concentrations. Finally, the Internal Exposure Uptake Biokinetic Model for Lead in Children (IEUBK Model) of the US Environmental Protection Agency (EPA) was employed to estimate realistic blood lead levels (BLLs) in children under five years of age, based on Pb concentrations measured in the water.
Of the 18 pumps sampled, 15 produced at least one sample exceeding the World Health Organization (WHO) provisional guideline of 10 [um]g/L dissolved Pb in water. Specifically, 67% of all samples showed concentrations above 10 [um]g/L under first-draw pumping conditions. Flushing the pumps prior to use decreased the Pb levels significantly (p < 0.0001), with only 35% of samples exceeding the provisional guideline. Under flushed conditions, the median Pb concentration in pumped water was 9 [um]g/L, down from 13 [um]g/L at one hour of inactivity. No statistically significant correlations were observed between measured Pb concentrations and factors like the season of sample collection, pump age, manufacturer, or water quality indicators like pH or temperature. Under first-draw conditions, the concentration of Pb in water increased with increasing duration of pump inactivity, until equilibrium was reached with the leaded pump components. For two pumps, substitution of Fe valves for Pb greatly decreased Pb concentrations in the water, from 37-100 [um]g/L and 7-24 [um]g/L down to 3-4 [um]g/L and 2-8 [um]g/L, respectively. Model-predicted geometric mean BLLs in children range from about 2-8 [um]g/dL, in some instances exceeding the Centers for Disease Control and Prevention (CDC) guideline for an elevated BLL (5 [um]g/dL), depending on the exposure concentrations.
This study finds that water provided by Pitcher Pump systems in Madagascar frequently exceeds the WHO provisional guideline value for safe consumption under first-draw conditions, and may do so even after flushing the pumps. The Pb concentrations measured in the field have the potential to elevate BLLs in children under five to levels implicated in serious health issues. Leaching of Pb into the water is therefore an issue of concern for users of the Pitcher Pump systems in Tamatave, and likely for other areas served by this technology. Flushing the pumps before water collection generally reduces Pb levels in the water. These results suggest that most of the Pb leaches from pure Pb check valve weights at the mouth of the pump, and consequently, a substitution of Fe weights on the valves greatly reduces Pb concentrations and the probability for exceeding the WHO provisional guideline. Relatively simple operational changes on the part of the pump manufacturers and the pump users might, therefore, help to ensure the continued sustainability of Pitcher Pumps in eastern Madagascar.
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Nanocomposite-graphene based platform for heavy metal detectionWillemse, Chandre Monique January 2010 (has links)
This study reports the synthesis of graphene by oxidizing graphite to graphite oxide using H2SO4 and KMnO4 and reducing graphene oxide to graphene by using NaBH4. Graphene was then characterized using FT-IR, TEM, AFM, XRD, Raman spectroscopy and solid state NMR. Nafion-Graphene in combination with a mercury film electrode, bismuth film electrode and antimony film electrode was used as a sensing platform for trace metal analysis in 0.1 M acetate buffer (pH 4.6) at 120 s deposition time, using square-wave anodic stripping voltammetry (SWASV). Detection limits were calculated using 3Ïblank/slope. For practical applications recovery studies was done by spiking test samples with known concentrations of metal ions and comparing the results to inductively coupled plasma mass spectrometry (ICPMS). This was then followed by real sample analyses.
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Nanocomposite-graphene based platform for heavy metal detectionWillemse, Chandre Monique January 2010 (has links)
This study reports the synthesis of graphene by oxidizing graphite to graphite oxide using H2SO4 and KMnO4 and reducing graphene oxide to graphene by using NaBH4. Graphene was then characterized using FT-IR, TEM, AFM, XRD, Raman spectroscopy and solid state NMR. Nafion-Graphene in combination with a mercury film electrode, bismuth film electrode and antimony film electrode was used as a sensing platform for trace metal analysis in 0.1 M acetate buffer (pH 4.6) at 120 s deposition time, using square-wave anodic stripping voltammetry (SWASV). Detection limits were calculated using 3Ïblank/slope. For practical applications recovery studies was done by spiking test samples with known concentrations of metal ions and comparing the results to inductively coupled plasma mass spectrometry (ICPMS). This was then followed by real sample analyses.
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Μεταβολές των ανόργανων οφθαλμικών συστατικών στο σύνδρομο της ψευδοαποφολίδωσηςΠαντελή, Βασιλική 30 May 2012 (has links)
Σκοπός της μελέτης ήταν ο ποσοτικός προσδιορισμός των ιχνοστοιχείων βαρέων μετάλλων του ψευδαργύρου, καδμίου και χαλκού στο υδατοειδές υγρό ασθενών με ψευδοαποφολίδωση και η μέτρηση του δυναμικού οξειδοαναγωγής στο υδατοειδές αυτών των ασθενών.
Υλικό και μέθοδοι: Δείγματα υδατοειδούς υγρού ελήφθησαν κατά την εγχείρηση καταρράκτη από 14 ασθενείς με PEX σύνδρομο (7 άνδρες και 7 γυναίκες) και 21 ασθενείς με καταρράκτη αλλά χωρίς PEX (9 άνδρες και 12 γυναίκες). Τα δείγματα διατηρήθηκαν στους -24C μέχρι την ανάλυση. Τα επίπεδα των τριών μετάλλων και στις δύο ομάδες προσδιορίστηκαν, για πρώτη φορά στην Οφθαλμολογία, με τη μέθοδο της βολταμετρίας με χρήση ηλεκτροδίων υαλώδους γραφίτη με υμένιο υδραργύρου, ενδεικτικού ηλεκτροδίου λευκόχρυσου και αναφοράς Ag/AgCl. Εφαρμόσθηκε η τεχνική της ανοδικής βολταμετρίας απογύμνωσης με τετραγωνικούς παλμούς και έγινε σύγκριση των τιμών ανάμεσα στις δύο ομάδες. Η στατιστική επεξεργασία των αποτελεσμάτων έγινε με το Mann-Whitney test (p<0.05)
Στη συνέχεια, κατά τον ίδιο τρόπο, δείγματα υδατοειδούς ελήφθησαν από 13 ασθενείς με PEX (7 άνδρες/6 γυναίκες) και 22 ασθενείς χωρίς PEX (7 άνδρες/15 γυναίκες). Η μέτρηση του δυναμικού οξειδοαναγωγής γινόταν αμέσως μετά την απόκτηση του κάθε δείγματος και για το σκοπό αυτό χρησιμοποιήθηκε για πρώτη φορά στην Οφθαλμολογία, ένα μικροηλεκτρόδιο λευκοχρύσου μαζί με ένα ενσωματωμένο ηλεκτρόδιο αναφοράς Ag/AgCl/KCl. Η στατιστική ανάλυση των αποτελεσμάτων έγινε με το t-test για ανεξάρτητα δείγματα (p<0.05).
Αποτελέσματα: O Cu βρέθηκε στατιστικά σημαντικά χαμηλότερος στην PEX ομάδα σε σχέση με τη φυσιολογική ομάδα (p<0.05), ενώ ο Zn και το Cd δεν παρουσίασαν καμία συσχέτιση στο υδατοειδές υγρό ασθενών με ψευδοαποφολίδωση.
Το δυναμικό οξειδοαναγωγής ήταν στατιστικά σημαντικά υψηλότερο στο υδατοειδές των ασθενών με PEX σύνδρομο.
Συμπεράσματα: Στην παρούσα εργασία εφαρμόζεται για πρώτη φορά, η ανοδική βολταμετρία απογύμνωσης για τον προσδιορισμό στο υδατοειδές υγρό του Zn, Cd και Cu και η μέτρηση του δυναμικού οξειδοαναγωγής στο υδατοειδές. Τόσο τα στατιστικώς σημαντικά χαμηλότερα επίπεδα Cu στο υδατοειδές ασθενών με PEX, όσο και το υψηλότερο δυναμικό οξειδοαναγωγής στο υδατοειδές αυτών των ασθενών ενισχύουν την παθογενετική θεωρία του οξειδωτικού στρες του PEX συνδρόμου. / To determine the Zn, Cd and Cu concentrations in aqueous humor of patients with PEX syndrome and to evaluate the overall oxidative status of the aqueous in this group by measuring the reduction-oxidation (redox) potential in the aqueous samples.
Material and methods: Samples from aqueous humor were collected during cataract extraction from 14 patients with PEX syndrome (7 male/7 female) and 21 patients without PEX (9 male/12 female). All samples were stored in -24C until analyzed. The levels of selected trace elements in both groups were assayed for the first time in the field of Ophthalmology, with anodic stripping voltammetry, using the square wave differential pulse technique. In this analytical procedure a glassy carbon mercury film electrode, a platinum indicator and a reference Ag/AgCl electrode were used. Finally the metal levels in all samples were compared between the two groups using the Mann-Whitney test (p<0.05).
Similarly, samples were collected during cataract extraction from 13 patients (7 male/6 female) with PEX syndrome and 22 normal patients (7 male/15 female). A platinum electrode together with a reference electrode Ag/AgCl/KCl was used for the first time in Ophthalmology, for the measurement of the apparent redox potential in the aqueous humor. The independent samples t-test was used to compare aqueous redox potential between the study and control group. Statistical significance was set at 0.05.
Results: Cu was found significantly lower in the PEX than in the control group (p<0.05), whereas Zn and Cd had no statistical differences between the two groups.
The redox potential was found significantly higher in patients with PEX syndrome than in normal patients (p<0.05).
Conclusions: In the present study we represent the first successful application of ASV in eye research for the determination of aqueous Zn, Cd and Cu concentrations and the meauserment of aqueous redox potential. The significantly lower Cu concentrations and the higher redox potential in aqeous humor of PEX syndrome support the role of increased oxidative stress in the development of PEX.
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Voltametria adsortiva na determinação de traços e ultra-traços de Zr(IV), V(V),Ti(IV), Mo(VI), Hf(IV), Nb(V) e Ta(V) em águas naturais / Adsorptive voltammetry in the determination of traces and ultra-traces of Zr(IV), V(V), Ti(IV), Mo(VI), Hf(IV), Nb(V) e Ta(V) in natural watersSchneider, Alexandre Batista 13 March 2014 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Single sensitive sequential AdSV methods were developed and optimized for the determination of trace zirconium, vanadium, titanium and molybdenum in river, estuary and seawater, independent of the salinity and content of organic matter in the sample. The methods are based on the accumulation of Zr(IV)-and V(V)-cupferron-oxalic acid-1,3-diphenylguanidine complexes and the accumulation of Ti(IV)-and Mo(VI)-mandelic acid at the hanging mercury drop electrode (HMDE). Differential pulse, adsorption potential of -0.6, -0.2, -0.1 and -0.1 V (vs. Ag/AgCl), adsorption time of 400, 20, 120 and 1 s and scan rates of 0.01, 0.06, 0.02 and 0.02 V s-1 for Zr(IV), V(V), Ti(IV) and Mo(VI), respectively, were used as instrumental parameters. The reduction peak for the complexes of Zr(IV), V(V), Ti(IV) and Mo(VI) appeared nearly -0.95, -0.65, -0.85 and -0.4 V, respectively. The variations of the peak current as well as the peak potential of each metal complexes were plotted against the apparent ionic strengths. The proposed voltammetric methods were applied in German and Brazilian rivers and estuaries as well as in seawater from the North Sea collected at the north of Germany and the Atlantic Ocean, collected during scientific cruise between Chile and Germany, as interesting and very simple alternatives to very laborious and time-consuming pre-existent methods, based on outline pre-concentration and separation from the matrix and subject to external contamination. The limits of detection and determination were in the range of ppt-levels and the methods accuracy were evaluated by recoveries tests and by measuring V(V) and Mo(VI) in two NRCC reference materials. Estuarine mixtures experiments were also carried out with the aim to get more insight on the distribution of Ti(IV), Zr(IV), Mo(VI) and V(V) along the estuaries of the rivers Rhine, Weser and Elbe with the North Sea. In this context, natural fresh waters were mixed with seawater at different ratios. / Métodos sensíveis e sequenciais de voltametria adsortiva de redissolução foram desenvolvidos e otimizados para a determinação de traços e ultra-traços de zircônio, vanádio, titânio e molibdênio em águas de rio, estuário e mar, independentemente da salinidade e conteúdo de matéria orgânica na amostra. Os métodos são baseados na acumulação de complexos de Zr(IV) e V(V) com cupferron-ácido oxálico-1,3-difenilguanidina e de complexos de Ti(IV) e Mo(VI) com ácido mandélico no eletrodo de mercúrio de gota pendente (HMDE). Pulso diferencial, potenciais de adsorção de -0,6; -0,2; -0,1 e -0,1 V (vs Ag/AgCl), tempos de adsorção de 400, 20, 120 e 1 s e velocidades de varredura de 0,01; 0,06; 0,02 e 0,02 V s-1, para Zr(IV), V(V), Ti(IV) e Mo(VI), respectivamente, foram usados como parâmetros instrumentais. Os picos de redução para os complexos de Zr(IV), V(V), Ti(IV) e Mo(VI) surgiram próximos de -0,95; -0,65; -0,85 e -0,4 V, respectivamente. As variações de corrente de pico assim como de potencial de pico de cada complexo dos metais foram plotados contra as forças-iônicas aparentes das amostras. Os métodos voltamétricos propostos foram aplicados em águas de rio e estuário coletadas na Alemanha e no Brasil e em amostras de água do mar do Mar do Norte coletadas no norte da Alemanha e Oceano Atlântico, coletadas durante expedição científica entre o Chile e Alemanha. Estes métodos se mostraram ser alternativas simples a métodos bastante complexos e demorados, baseados em pré-concentração outline e separação da matriz, sujeitos a contaminação externa. Os limites de detecção e quantificação estavam na ordem de partes por trilhão e a exatidão dos métodos foi avaliada através de teste de recuperação de amostras adicionadas com os analitos em estudo e em 2 materiais de referência certificados. Também foram realizados experimentos de mistura estuarina com o objetivo de obter informações da distribuição de Ti(IV), Zr(IV), Mo(VI) e V(V) ao longo de estuários dos rios Reno, Weser e Elba com o Mar do Norte. Neste intuito, as águas dos rios e do mar foram misturadas em diferentes razões.
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[en] DEVELOPMENT AND COMPARISON OF VOLTAMMETRIC METHODS FOR THE DETERMINATION OF CYCLOFENIL AND PRIMAQUINE IN PHARMACEUTICAL FORMULATIONS AND IN URINE / [pt] DESENVOLVIMENTO E COMPARAÇÃO DE MÉTODOS VOLTAMÉTRICOS PARA A DETERMINAÇÃO DE CICLOFENIL E PRIMAQUINA EM MEDICAMENTOS E EM URINAWAGNER FELIPPE PACHECO 13 July 2004 (has links)
[pt] Neste trabalho foram desenvolvidas metodologias
eletroanalíticas baseadas
na voltametria adsortiva de redissolução catódica com
varredura de potencial de
onda quadrada e de pulso diferencial para a determinação do
ciclofenil em urina e
em formulações farmacêuticas, e na voltametria anódica com
varredura de
potencial de onda quadrada e de pulso diferencial para a
determinação da
primaquina em formulações farmacêuticas. Comparando-se as
duas técnicas de
aquisição, a voltametria de onda quadrada foi escolhida
para realizar as
determinações do ciclofenil em urina e em formulação
farmacêutica por se
mostrar, além de uma técnica mais rápida, maior
sensíbilidade. Para a
determinação da primaquina a melhor técnica foi à
voltametria de pulso
diferencial.
As condições experimentais que possibilitaram um melhor
desempenho
analítico em termos da obtenção do menor limite de detecção
e maior
reprodutibilidade das leituras foram otimizados. No caso do
ciclofenil, o
composto mostrou ser instável no meio aquoso e orgânico
para determinação
voltamétrica, com sistemática diminuição da corrente
faradaica. Assim, fez-se uso
das propriedades eletroquímicas de um derivado estável
obtido pela derivatização
fotoquímica do composto (o composto foi irradiado com
irradiação UV por 45
minutos em um reator fotoquímico), a corrente máxima obtida
apresentou um
potencial a -1,28 V. As condições experimentais que
possibilitaram este sinal
foram obtidas com 30 s de tempo de deposição do analito
sobre o eletrodo de
mercúrio, solução Britton-Robbinson pH 9,0 como eletrólito
de suporte, potencial
de acumulação de -0,9 V, amplitude de 250 mV, incremento de
potencial de 2,0
mV no modo de onda quadrada.
Desta forma foi obtido limite de detecção da ordem de 10-8
mol L-1, faixa
linear dinâmica de 2 ordens de grandeza, condições estas
que possibilitaram a
determinação do composto tanto em formulações farmacêuticas
(Menopax)
como em amostra de urina enriquecida com o analito de
interesse. Foram feitos
testes com subtâncias concomitantes da formulação
farmacêutica e constatou-se
que não existia problema com interferência na análise nesse
tipo de amostra. Nas
determinações em urina não houve a necessidade de se fazer
tratamento prévio da
amostra, apenas a irradiação UV para estabilizar o
composto, as análises foram
realizadas com o método de adição de analito, de forma a se
corrigir a
interferência de matriz. Em ambos os casos os resultados
obtidos se encontram na
faixa de 93,6 a 106,5 por cento, dentro da faixa de recuperação
aceitável para este tipo de
problema analítico segundo estabelecido pela Farmacopéia
dos Estados Unidos da
América.
Usou-se ainda os resultados provenientes das voltametrias
de pulso
diferencial, de voltametria de onda quadrada e da
voltametria cíclica para se obter
informações sobre o processo redox que ocorria no eletrodo
de trabalho.
Constatou-se que a reação é reversível, com um processo de
controle adsortivo,
sendo que apenas o reagente adsorve no eletrodo de
trabalho, não ocorrendo
adsorção do produto da reação de redução. Constatou-se
também que o processo
envolve a transferência de apenas 1 elétron, e que a reação
não possuía
contribuição cinética.
No caso da primaquina o sinal de redução ocorre em região
anódica (0,592
V), foi portanto necessário utilizar um eletrodo de carbono
para se poder fazer a
determinação da primaquina. Visando a possibilidade do uso
do eletrodo de
mercúrio, tentou-se fazer uso da formação de derivados
complexos da primaquina
com vanádio, com cobre ou com íon iodeto (complexo de
tranferência de carga),
porém não foram observados sinal da reação redox na janela
de potencial
procurada. Nas condições experimentais otimizadas não se / [en] In this work, square-wave and differential pulse
voltammetric methods were
developed for the determination of cyclofenil and
primaquine in pharmaceutical
formulations and in urine samples. The use of the square-
wave acquisition
technique was found to enable better sensitivity and faster
analysis time compared
to the differential pulse technique.
Experimental and instrumental conditions were optimized to
allow the best
analytical performance in terms of limit of detection and
repeatability of the
readings. In the case of cyclofenil, its unstable behavior
in aqueous and organic
solvents, with systematic decreasing of analyte current
signal, makes impossible
any voltammetric determination. As an alternative way, the
electrochemical
properties of a stable photochemical derivative of
cyclofenil was used (the
compound was irradiated with UV radiation for 45 min) with
maximum current at
-1,28 V. This analyte photoderivative could also be
accumulated in the working
electrode. The experimental conditions that allowed the
maximum current was a
30 s of deposition time at the mercury electrode, Britton-
Robbinson (pH 9,0)
supporting electrolyte, accumulation potential of -0,9 V,
amplitude of pulse of
250 mV, scan increment 2,0 mV.
These optimized conditions allowed a limit of detection of
10-8 mol L-1 and
dynamic linear range of 2 orders of magnitude to be
achieved. These analytical
figures of merit made possible the determination of
cyclofenil either in a
pharmaceutical formulation (Menopax) and in urine samples
spiked with the
analyte of interest. The potential interferences from
concomitant substances used
in the pharmaceutical formulation were also evaluated. For
the analyte
determination in urine, only UV irradiation of sample was
necessary, in order to
obtain stable cyclofenil derivative. The analyte addition
method was used to
analyze urine in order to minimize matrix interferences.
Recovery results for the
analysis of Menopax and for the analysis of urine were
between 96,5 and 107,6
percent, within the acceptable recovery range established by the
United States
Pharmacopoeia.
Information concerning the analyte redox reaction and
electrode processes
was also obtained from differential pulse voltammetry,
square-wave voltammetry
and cyclic voltammetry. It was verified that the cyclofenil
photoderivative
eletrochemical reaction is reversible with adsorption of
only the reagent on the
surface of the electrode. The adsorption of the
electrochemical reduction product
does not occur. It was also verified that the process
involves the transference of
only one electron, and there is no kinetics contribution in
the reaction.
In the case of the primaquine the analyte reduction occurs
in anodic region
(0,592 V), therefore, it was necessary the use the carbon
glass electrode to allow
the determination of this analyte. The pre-concentration of
the analyte in the
working carbon glass electrode was also not attained with
the experimental
conditions used.
Several attempts were made to make possible the use of the
mercury
electrode, including the formation of charge transfer
complexes with iodine and
complexation with vanadium. However no success was obtained.
Using the carbon glassy electrode and DPV technique the
determination of
primaquine in pharmaceutical formulations and urine was
performed with average
recovery of 101.7 percent. Limit of detention of 1,0 x 10-6 mol L-
1 was obtained.
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Desenvolvimento e validação de métodos voltamétricos sequenciais para a determinação de elementos em matrizes complexas / Development and validation of voltammetric sequential methods for the determination of elements in complex matricesMuratt, Diana Tomazi 07 August 2013 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Toxic elements are in continuous accumulation in the environment mainly due to anthropogenic activities. In this work, a voltammetric method of sequential analysis for application in matrices of complex characteristics was developed. Using an organic mixture complexing, SVRS (alizarin violet) DMG (dimethylglyoxime), 8-hydroxyquinoline (oxine), CA (chloranilic acid) and DTPA (diethylenetriaminepentaacetic acid) 13 elements could be determined at two different methods. According to the formation constants with their respective ligands, in method 1, step were determined Al3+, Fe3+, Mo6+ SVRS in the presence of AdSV (Adsorptive Stripping Voltammetry). In step 2 were determined Zn2+, Cd2+, Pb2+ and Cu2+ by ASV. In step 3, were determined Ni2+ and Co2+ in the presence of DMG and oxine. In method 2, V5+ and U6+ were determined by AdSV in the presence of CA (chloranilic acid), Cr(total) was analyzed in sequence by the presence of DTPA by AdSV and finally Tl+ was determined by ASV. The data for the figures of merit showed that the proposed method is suitable for samples of complex matrices studied (certified materials and commercial plant compounds). High concentrations for some elements were found in commercial samples. It indicates that the species translocates through the environment in which they are insert, being susceptible to contact with humans. / Elementos tóxicos estão em contínuo acúmulo no ambiente principalmente devido a atividades antropogênicas. Neste trabalho, foi desenvolvido um método voltamétrico de análise sequencial para aplicação em matrizes de natureza complexa. Utilizando uma mistura de complexantes orgânicos, SVRS (violeta de solocromo), DMG (dimetilglioxima), 8-Hidroxiquinolina (oxina), CA (ácido cloranílico) e DTPA (ácido dietilenotriamino pentaacético) foi possível determinar 13 elementos em dois diferentes métodos. De acordo com as constantes de formação com os respectivos ligantes foi determinado no método 1, etapa 1 Al3+, Fe3+, Mo6+ na presença de SVRS por AdSV (Adsorptive Stripping Voltammetry). Na etapa 2 determinou-se Zn2+, Cd2+, Pb2+, Cu2+ por ASV. Na etapa 3, foram determinados Ni2+ e Co2+, na presença de DMG e oxina. No método 2, U6+ e V5+ foram determinados por AdSV na presença de CA (ácido cloranílico), Cr(total) foi determinado na sequência na presença de DTPA por AdSV e por fim, Tl+ foi determinado por ASV. Os dados obtidos para as figuras de mérito mostraram que o método proposto é adequado para as amostras de matrizes complexas estudadas (materiais certificados e compostos vegetais comerciais). Concentrações altas para alguns elementos foram encontradas nas amostras comerciais. Este dado indica que as espécies translocam-se através do meio em que estão inseridos estando suscetíveis a entrar em contato com o ser humano.
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Determinação simultânea de Cd, Pb e Cu em amostras de chá (Camellia sinensis) por voltametria de onda quadrada e redissolução anódicaMedeiros, Cleilson Lucena de 31 August 2015 (has links)
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Previous issue date: 2015-08-31 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / This paper describes the development of a method for quantification Cd2+,
Pb2+ and Cu2+ cations, in teas, performed simultaneously, using Square
Wave Anodic Stripping Voltammetry carbon nanotube paste electrode
modified with bismuth film. Tea is one of the most beneficial and
consumed beverage through the world, being prepared from the infusion
parts of the plant Camellia sinensis. Most commonly this kind of tea
presents metal ions, such as Cd 2+, Pb 2+ and Cu 2+, which offers health
risk, in case of being ingested above the limit. To detect these metals, it
is necessary to make use of techniques with high sensitivity. The
spectrometric methods are the most widely used, but they have a high
cost, are laborious and expensive. The voltammetric techniques are
characterized by being inexpensive and having equal sensitivity, and even
greater than some spectrometric methods. The parameters of the
technique used were obtained after optimization with fractional factorial
design. The tea samples were prepared through digestion with heating by
microwave radiation in a closed system using diluted nitric acid and
hydrogen peroxide. The method was validated based on the sample
certified plant tissue (forage Marandu) and applied in green and black tea
samples. Recoveries of cations Cd 2+, Pb 2+ and Cu 2+ ranged from 79.3
to 107.6%, the certified sample, and 73.3 to 122.1% in the evaluated
samples of teas. The detection limits obtained in the simultaneous
analysis of Cd 2+, Pb 2+ and Cu 2+ were 0.16; 0.20; 0.39 ug L-1,
respectively. Cu2 + was detected only in samples of tea, but the method
was efficient for the simultaneous quantification of all metals in the matrix
assessed after the addition and recovery. / Este trabalho descreve o desenvolvimento de um método de quantificação
dos cátions Cd2+, Pb2+ e Cu2+, em chás, realizada de forma simultânea,
empregando voltametria de onda quadrada por redissolução anódica com
eletrodo de pasta de nanotubo de carbono modificado por filme de
bismuto. O chá é uma das bebidas mais benéficas e consumidas no
mundo, sendo preparado a partir da infusão de partes da planta Camellia
sinensis. Normalmente são encontrados cátions metálicos, como o Cd2+,
Pb2+ e Cu2+, que se ingeridos acima do limite máximo representam riscos
à saúde. Para detectar esses metais é necessário fazer uso de técnicas
com alta sensibilidade. Os métodos espectrométricos são os que mais
amplamente tem sido utilizado, porém apresentam custo elevado, são
laboriosos e dispendiosos. As técnicas voltamétrica caracterizam-se por
serem baratas e possuir sensibilidade igual e até maior que alguns
métodos espectrométricos. Os parâmetros da técnica utilizada foram
obtidos após otimização com planejamento fatorial fracionário. As
amostras de chá foram preparadas via digestão com aquecimento por
radiação micro-ondas em sistema fechado empregando ácido nítrico e
peróxido de hidrogênio diluídos. A validação do método foi realizada com
base na amostra certificada de tecido vegetal (forrageira Marandu) e
aplicada em amostras de chá verde e preto. As recuperações dos cátions
Cd2+, Pb2+ e Cu2+ variaram de 79,3 a 107,6%, na amostra certificada, e
de 73,3 a 122,1% nas amostras de chás avaliadas. Os limites de detecção
obtidos na análise simultânea de Cd2+, Pb2+ e Cu2+, foram 0,16; 0,20;
0,39 μg L-1, respectivamente. Foi detectado apenas Cu2+ nas amostras de
chá, porém o método se mostrou eficiente para quantificação simultânea
de todos os metais na matriz avaliada após a adição e recuperação.
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Determinação voltamétrica de zinco empregando eletrodos quimicamente modificados com bismutoFonseca, Wilson Tiago da 18 July 2016 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Esta dissertação apresenta o desenvolvimento de métodos voltamétricos para a determinação de zinco em amostras comerciais de polivitamínicos, talco e materiais artísticos para pintura (giz pastel) combinando uma extração alcalina com solução aquosa de NaOH 1,0 mol L-1 e eletrodos quimicamente modificados com bismuto. Foram utilizados dois eletrodos para a quantificação de zinco nas amostras, eletrodo de filme de bismuto (BiFE) crescidos in situ sobre carbono vítreo e eletrodo de pasta de carbono quimicamente modificado com a resina de troca iônica fortemente ácida Amberlite® IR 120 e nanoestruturas de bismuto (EPCAmbBi). Verificou-se que a melhor concentração de Bi3+ para o crescimento do filme de Bi sobre carbono vítreo foi 4,0 μmol L-1 utilizando uma solução aquosa de tampão acetato 0,1 mol L-1 (pH = 4,5) como eletrólito de suporte. A melhor condição para a formação das nanoestruturas de Bi no EPC modificado com 10% de Amberlite® IR 120 foi a utilização de 30 s de pré-concentração (circuito aberto) em uma solução aquosa de Bi3+ 0,5 mmol L-1 (pH = 5,5) preparada com a solução do eletrólito de suporte. A curva analítica obtida para o Zn2+ utilizando o BiFE apresentou uma região linear de 0,5 a 5,0 μmol L-1 o valor de Limite de Detecção (LD) foi de 41 nmol L-1. Para o EPCAmbBi foi observado um único intervalo linear na curva analítica construída variando a concentração do Zn2+ de 0,05 a 8,2 μmol L-1, o LD obtido nesta curva foi igual a 10 nmol L-1. O EPCAmbBi apresentou picos de redissolução anódica para Zn2+ mais intensos e estreitos e, portanto, com melhor perfil voltamétrico, com uma sensibilidade superior à obtida com o BiFE. Além disso, o EPCAmbBi apresentou um LD menor do que o obtido com o BiFE. A extração alcalina foi um procedimento de pré-tratamento de amostra eficiente para extrair o Zn2+ da matriz de amostras sólidas, além disso, este método de extração é menos susceptível à interferências do Cu2+, uma vez que este permanece insolúvel como Cu(OH)2 durante a extração. A combinação da extração alcalina com o EPCAmbBi mostrou-se uma forma simples, rápida, eficiente e de baixo custo para a determinação de zinco em amostras de formulações farmacêuticas e de materiais artísticos para pintura (giz pastel), podendo ser empregada como um método alternativo e de menor custo em relação à espectroscopia de absorção atômica. / This dissertation presents the development of voltammetric methods to zinc determination in multivitamin commercial samples, talc, and art materials for painting (soft pastel) combining an alkaline extraction with 1.0 mol L-1 NaOH aqueous solution and bismuth modified electrodes. Two electrodes were used to zinc quantification in the samples, bismuth film electrode (BiFE) plated in situ onto glassy carbon and carbon paste electrode chemically modified with strongly acidic ion exchange resin Amberlite® IR 120 and bismuth nanostructures (EPCAmbBi). It was verified that the best concentration of Bi3+ for Bi film deposition onto glassy carbon was 4.0 μmol L-1 using an 0.1 mol L-1 acetate buffer aqueous solution (pH = 4.5) as supporting electrolyte. The best condition to formation of Bi nanostructures in the EPC modified with 10 % Amberlite® IR 120 was the use of 30 s to pre-concentration (open circuit) in 0.5 mmol L-1 Bi3+ aqueous solution (pH 5.5) prepared with supporting electrolyte solution. The obtained analytical curve for Zn2+ using BiFE presented linear range from 0.5 to 5.0 μmol L-1, the limit of detection (LD) was 41 nmol L-1. For EPCAmbBi only one linear range was observed for the analytical curve varying the Zn2+ concentration from 0.05 to 8.2 μmol L-1, LD obtained in this curve it was equal to 10 nmol L-1. The EPCAmbBi presented the most intense and sharp anodic stripping peaks for Zn2+ presenting, therefore, a better voltammetric profile, with sensitivity higher than obtained with the BiFE. Moreover, the EPCAmbBi presented a LD lower than that obtained with the BiFE. Alkaline extraction was an efficient sample pretreatment to extract Zn2+ from solid samples, besides that, this procedure was less susceptible to interferences from Cu2+, since it remains at extracting vessel as insoluble Cu(OH)2. The combination of alkaline extraction with the EPCAmbBi is a simple, fast, efficient and low cost for the zinc determination in pharmaceutical formulations and art materials for painting (soft pastel) samples, which can be employed as a low-cost alternative method to the atomic absorption spectroscopy. / Dissertação (Mestrado)
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