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Título: SPECTROANALYTICAL METHODS USING GRAPHENE QUANTUM DOTS AS PHOTOLUMINESCENT PROBES FOR THE DETERMINATION OF ANALYTES OF BIOLOGICAL AND PHARMACOLOGICAL INTEREST
Autor: CARLOS ALBERTO TOLOZA TOLOZA
Instituição: PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO - PUC-RIO
Colaborador(es):  RICARDO QUEIROZ AUCELIO - ADVISOR
SARZAMIN KHAN - CO-ADVISOR

Nº do Conteudo: 35904
Catalogação:  20/12/2018 Idioma(s):  ENGLISH - UNITED STATES
Tipo:  TEXT Subtipo:  THESIS
Natureza:  SCHOLARLY PUBLICATION
Nota:  Todos os dados constantes dos documentos são de inteira responsabilidade de seus autores. Os dados utilizados nas descrições dos documentos estão em conformidade com os sistemas da administração da PUC-Rio.
Referência [pt]:  https://www.maxwell.vrac.puc-rio.br/colecao.php?strSecao=resultado&nrSeq=35904@1
Referência [en]:  https://www.maxwell.vrac.puc-rio.br/colecao.php?strSecao=resultado&nrSeq=35904@2
Referência DOI:  https://doi.org/10.17771/PUCRio.acad.35904

Resumo:
The objective of the present work was the development of spectroanalytical methods capable of indirectly determining analytes of biological and pharmacological interest that present inherent weak optical activity in UV-vis (in this case, captopril, histamine and kanamycin sulfate). Although many methods to quantify these analytes are reported, many of these depend on chemical derivatization, a procedure considered complex and laborious to promote UV-vis absorption and luminescence. Therefore, the proposed use of photoluminescent quantum dots is interesting since they allow, under adjusted conditions, analytical responses that allow the indirect determination of the analytes of interest in concentrations of the order of down to 10-8 mol L-1. The determination of captopril was proposed using graphene quantum dots aminofunctionalized using glutathione as a precursor (GQDs-amino). Captopril induced photoluminescence suppression and spectral red-shift from the aqueous dispersion of GQDs-amino. In contrast, when Fe3+ is used as a mediator, it generates a suppression of the photoluminescence of the GQD-amino dispersion and the addition of captopril restored the original photoluminescence of the quantum dots. In adjusted experimental conditions, photoluminescence suppression of the GQDs-amino, as a function of the captopril concentration, can be related both to the magnitude of the suppression and to the spectral shift. In both cases, the linearized response covered three orders of magnitude (10-6 to 10-4 mol L-1). In contrast, the probe signal restoration of the previously Fe3+ suppressed photoluminescent GQDs, also proved to be analytically useful. The proposed approaches were tested by the determination of captopril in simulated samples and in commercial pharmaceutical formulations. Spectral shift from the GQDs-amino probe and the photoluminescence on/off approach (using GQDs-amino-Fe3+ probe) resulted in satisfactory recoveries, showing the quantitative capability of the method. In the work concerning histamine, the photoluminescent behavior of the aqueous dispersion of GQDs-amino in the presence of this amino acid was studied in function of different interaction mediators (metal ions). The results revealed that strong and selective interaction existed in the presence of Eu3+, Fe3+ and Cu2+. The sensitivity of normalized photoluminescence (Ks) suppression curves indicated a ten-fold stronger interaction of histamine with the surface of GQDs in the presence of Fe3+. The linear response observed in the GQDs-amino-Fe3+ (luminescence measured at 345/435 nm) covered the histamine concentration of 4.3 × 10-7 mol L-1 (quantification limit) to 3.2 × 10-5 mol L-1. The GQDs-amino-Fe3+ was applied as a probe in the analysis of tuna fish samples after solid phase extraction (SPE) of the analyte using a cationic solid phase. The analytical results were statistically similar to those obtained with a method based on liquid chromatography with fluorimetric detection (after chemical derivatization of histamine). The determination of kanamycin sulfate was made by measuring the effect it exerts on the photoluminescence of gold nanoparticles (AuNPs) associated GQDs, that were produced by the reduction of AuCl4 with NaBH4 in an aqueous dispersion of GQDs-amino (obtained by pyrolysis of citric acid and glutathione) also containing the cationic surfactant CTAB. The AuNPs-GQDs-amino-CTAB system showed a suppressed photoluminescence, which was amplified in the presence of kanamycin. Under adjusted experimental conditions, the magnification of the photoluminescence of the nanomaterial as a function of the analyte concentration was linear and covered three orders of magnitude (10-7 to 10-5 mol L-1). The use of solid phase extraction with a cartridge packed with a molecularly imprinted polymer (selective for aminoglycosides) ensured selectivity in the determinations made in yellow fever vaccine and in veterinary pharmaceutical formulations. The analytical results were statistically similar to those obtained with an HPLC based method with fluorimetric detection (after chemical derivatization of kanamycin). The proposed methods for quantification present simple procedure, are very sensitive and selective, not involving the use of toxic reagents used for chemical derivatization.

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