https://repositorio.ufba.br/handle/ri/9057 Sat, 02 May 2026 18:48:31 GMT 2026-05-02T18:48:31Z https://repositorio.ufba.br/handle/ri/44433 Título: Proposição de métodos analíticos utilizando decomposição ácida e solubilização alcalina para determinação multielementar em amostras de méis e açúcares por técnicas empregando plasma indutivamente acoplado Autor(es): Melo, Joélem Carvalho de Primeiro Orientador: Araujo, Rennan Geovanny Oliveira Abstract: Honey and sugars contain carbohydrates and minerals and are widely consumed by the population. Due to daily consumption, generally in quantities exceeding 50 g, as recommended by the World Health Organization (WHO), it is necessary to evaluate the quality of these food products. This Doctoral Thesis aimed to propose analytical methods for the determination of inorganic constituents in honey and sugar samples using inductively coupled plasma (ICP) techniques. Firstly, a 2⁴⁻¹ fractional factorial design was applied to optimize the preparation of honey and sugar samples using a closed digestion block. The optimized condition involved the digestion of approximately 0.25 g of honey or sugar sample with the addition of 2.0 mol L⁻¹ HNO₃ and 3.0% m m-1 H₂O₂, in a reaction volume of 5.0 mL, heated to 180 °C for 120 minutes. The analytical method allowed the quantification of Al, As, Ba, Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Se, Sn, and Zn using inductively coupled plasma optical emission spectrometry (ICP OES). The limits of quantification (LOQ) values ranged from 0.01 (Ba) to 35 (S) mg kg⁻¹. The accuracy of the analytical method was confirmed through the analysis of certified reference materials (CRMs) of tomato leaves (CRM-Agro 1003a) and sugarcane leaves (CRM-Agro 1005a), obtaining a precision expressed as relative standard deviation (%RSD) of less than 11% (n=3) for all analytes. Forty-seven samples of honey (22) and sugars (25) were analyzed and the analytical method showed simplicity, accuracy, precision and a favorable environmental profile with the Green Chemistry concept (AGREE: 0.57). Essential and potentially toxic elements (EPTE) were determined in honeys and sugars by inductively coupled plasma mass spectrometry with triple quadrupole (ICP-MS/MS), with LOQ values between 0.002 (Cd) and 1.4 (Zn) mg kg⁻¹. Precision and accuracy were evaluated through analysis of CRMs from tomato leaves (CRM-Agro 1003a) and sugarcane leaves (CRM-Agro 1005a), showing good quantitative analysis. The concentrations were determined by ICP-MS/MS and the health risk for adults was estimated by the total target risk quotient (TTHQ), obtaining a value of 1.11 × 10⁻⁴ for honey and 8.24 × 10⁻¹ for sugar, indicating the absence of significant risk for non-carcinogenic effects from the ingestion of these foods containing EEPT. The second study developed an analytical method employing alkaline solubilization with tetramethylammonium hydroxide (TMAH) assisted by ultrasonic energy to determine the concentrations of Al, Ba, Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn in honey samples by ICP OES. A full 2³ factorial design was applied, and the chosen variables were: TMAH volume (100-500 µL at 25% m v-1 in methanol), thermostatic heating (40°C and 80°C), and sonication time (10-40 min). The best established condition employed approximately 0.25 g of honey sample, with the addition of 100 µL of TMAH, made up to 3 mL with deionized water, applying thermostatic heating at 80°C and a sonication time of 10 minutes. Afterwards, the resulting solution was made up to a volume of 10 mL with deionized water and analyzed by ICP OES. The analytical method showed good accuracy (recoveries between 88.0% and 107.5%) and precision (%RSD ≤ 4.6%), being applied to 22 honey samples collected in Bahia. The second analytical method was efficient, fast, reliable, and environmentally friendly, obtaining an AGREE rating of 0.73. Therefore, in this work, the different analytical methods developed were reliable and efficient, and can contribute to quality control of honeys and sugars in routine chemical analyses, considering that there are no standardized methods for quantitative analysis currently available. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Tese Mon, 15 Dec 2025 00:00:00 GMT https://repositorio.ufba.br/handle/ri/44433 2025-12-15T00:00:00Z https://repositorio.ufba.br/handle/ri/44392 Título: Nanofibras cerâmicas eletrofiadas como nanozymes: síntese, caracterização e aplicação em sensores colorimétricos Autor(es): Lima, Jéssica Brito dos Santos Primeiro Orientador: Mercante, Luiza Amim Abstract: The increasing demand for food safety and access to potable water has spurred the development of simple, rapid, and low-cost analytical methods for determining chemical species of interest. However, although highly sensitive, conventional analytical techniques often require expensive instrumentation, extensive laboratory infrastructure, and long analysis times. In this context, nanozyme-based colorimetric sensing has emerged as a promising alternative. Nanozymes are nanomaterials that mimic the catalytic activity of natural enzymes, promoting the oxidation of chromogenic substrates and producing color changes that enable the detection and quantification of analytes. Among the materials investigated for this purpose, metal oxides have attracted significant attention due to their high chemical stability and catalytic activity. However, the use of ceramic nanofibers in nanozyme-based platforms remains limited, despite their structural advantages, such as high surface area and one-dimensional morphology, which can enhance catalytic performance. In this work, precursor nanofiber membranes containing zinc and manganese salts were produced by electrospinning and subsequently calcined to yield ceramic nanofibers (NFII, NFIII, NFIV, and NFV) with compositions controlled by the metal salt ratio. The physicochemical properties of the materials were characterized by scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction, X-ray photoelectron spectrometry, and nitrogen physisorption, enabling correlations between morphology, composition, crystalline structure, and surface area. The oxidase-like activity of the nanofibers was evaluated using the chromogenic substrates tetramethylbenzidine (TMB), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and o-phenylenediamine (OPD), yielding kinetic parameters (Km and Vmax) comparable to or higher than those reported in the literature. Based on this catalytic activity, colorimetric sensors were developed for the determination of nitrite and ascorbic acid. The NFII/TMB system was applied to nitrite detection using ratiometric, spectrophotometric, and smartphone-assisted approaches, with limits of detection (LOD) of 4.0 and 4.8 µmol L-1, respectively. For ascorbic acid determination, the NFIII/ABTS and NFIII/OPD systems showed LODs of 0.7 and 1.5 µmol L-1, respectively. The developed sensors showed good sensitivity, selectivity, and stability, and were successfully applied to the determination of the analytes in drinking water and fruit juice samples, with recoveries ranging from 92.0 to 104.9%. These results demonstrate the potential of electrospun ceramic nanofibers as nanozymes for developing simple, accessible colorimetric platforms for food and water quality monitoring. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Tese Fri, 10 Apr 2026 00:00:00 GMT https://repositorio.ufba.br/handle/ri/44392 2026-04-10T00:00:00Z https://repositorio.ufba.br/handle/ri/44138 Título: Estratégias baseadas em química verde para microextração em fase líquida e determinação de mercúrio em frutos do mar Autor(es): Assis, Rosivan dos Santos de Primeiro Orientador: Lemos, Valfredo Azevedo Abstract: The use of increasingly eco-friendly solvents has been a guiding principle in liquid-phase microextraction (LPME). A solvent can be considered green when it exhibits low toxicity, biodegradability, low cost, and good availability. In this work, two microextraction methods were developed, employing different green solvents for the preconcentration and determination of mercury in seafood samples. In both studies, the reagent ammonium pyrrolidinedithiocarbamate (APDC) was used as a complexing agent, and detection was performed by cold vapor atomic absorption spectrometry (CV AAS). The first study proposes a simple approach based on microextraction with a switchable hydrophilicity solvent (SHS-DLPME). Octanoic acid (C8H16O2) was chosen as the SHS, and sodium carbonate was used as a CO2 source to change the polarity of the extraction solvent. After optimization, the detection limit was 0.010 mg kg-1, and the enrichment factor was 31. The second approach involved a vortex-assisted magnetic deep eutectic solvent dispersive liquid-phase microextraction (VA-MDES-DLPME). The MDES was produced from menthol and octanoic acid, used as proton acceptor and donor, respectively, and incorporated into magnetic iron nanoparticles. For this method, the enrichment factor was 51.4, while the detection limit was 0.009 mg kg-1. Certified reference materials BCR 414 (plankton), BCR 482 (lichen), and ERM-CE 278K (mussel tissue) were used for validation. The methods were applied to determine mercury in fish, mollusk, and crustacean samples, with mercury concentrations ranging from 0.11 to 0.37 mg kg-1 in both methods. The SHS-DLPME and VA-MDES-DLPME methods scored 0.60 and 0.57, respectively, on the AGREE metrics. The results demonstrated that both methodologies align with the principles of green chemistry by providing efficient, selective, and more environmentally friendly alternatives for mercury determination. Overall, the proposed procedures significantly advance sustainable microextraction strategies for contaminant analysis in food. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Tese Thu, 18 Dec 2025 00:00:00 GMT https://repositorio.ufba.br/handle/ri/44138 2025-12-18T00:00:00Z https://repositorio.ufba.br/handle/ri/43676 Título: Síntese verde de ZnO puro e compósito magnético com Fe₃O₄ usando extrato da folha do dendezeiro para remediação fotocatalítica de norfloxacino Autor(es): Ramos, Luana Tássia dos Santos Primeiro Orientador: Silva, Luciana Almeida da Abstract: A primary global concern in recent decades has been the improper disposal of pharmaceutical drugs due to their interaction with the ecosystem. Therefore, it is necessary to develop materials and processes that can degrade these pollutants, thereby minimizing environmental impacts. Advanced oxidation processes are considered promising alternatives, such as photocatalysis employing metal oxides, like ZnO, as photocatalysts. Among the methods for synthesizing zinc oxide, green synthesis is considered less environmentally harmful. It produces economic and ecological materials that minimize the use of toxic chemicals and energy consumption. In this work, zinc oxides, with and without iron, were prepared through green synthesis using oil palm leaf extract for application in the photocatalytic degradation of the aqueous antibiotic norfloxacin. The results indicate that phytochemicals from the oil palm leaf extract act as directing agents in the formation of hexagonal pyramids and bipyramids of ZnO, depending on the synthesis conditions and the zinc precursor. The materials in question were characterized by TG/DTA, XRD, FTIR, RAMAN, DRS, SEM, EDX, BET, and pHZPC. The results show that ZnO in the wurtzite phase is obtained under different conditions and, in the presence of iron, forms the magnetic composite ZnO/Fe3O4. All materials presented a band gap below 3.0 eV, and the results of photocatalytic tests indicate that pure zinc oxide prepared with zinc nitrate without pH adjustment had the best photoactivity, with approximately 86% of the antibiotic degraded in only 60 minutes of irradiation. The results also indicate that the degradation mechanism of norfloxacin shows a significant contribution from photogenerated holes (h+), followed by •OH radicals. The insertion of iron resulted in the formation of a ZnO/Fe3O4 magnetic composite, with magnetite nanoparticles dispersed within the hexagonal ZnO pyramids. Light absorption in the visible range is enhanced by the presence of Fe3O4 nanoparticles, as is the photocatalytic activity, resulting in 90% degradation of the antibiotic within 60 minutes of irradiation. In this case, •OH radicals contributed more significantly to the degradation of norfloxacin than the photogenerated holes (h+). Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Tese Fri, 14 Nov 2025 00:00:00 GMT https://repositorio.ufba.br/handle/ri/43676 2025-11-14T00:00:00Z