https://repositorio.ufba.br/handle/ufba/522 2026-05-04T18:20:52Z 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 2025-12-15T00:00:00Z https://repositorio.ufba.br/handle/ri/44425 Título: Determinação sequencial de Cd, Cu, Mn e Pb utilizando análise de suspensão por FS-F AAS e avaliação da concentração de Hg em amostras de poeira urbana coletadas em Santo Amaro, Bahia, Brasil. Autor(es): Francisco, Rafael Ribeiro Primeiro Orientador: Araujo, Rennan Geovanny Oliveira Abstract: This master’s dissertation addresses the development, analytical performance characteristics, and application of analytical methods for the determination of trace metals in urban dust samples, with a focus on the environmental assessment of the urban area of Santo Amaro, Bahia, Brazil. The work was divided into two complementary parts, involving distinct analytical approaches and environmental and human health risk applications. In the first part, an analytical method was developed and optimized for the sequential determination of Cd, Cu, Mn, and Pb in urban dust using sample preparation in the form of slurry and detection by flame atomic absorption spectrometry (F AAS) in fast sequential mode (FS). The study of sample mass indicated that the range between 10 and 75 mg provided the most suitable condition for the suspension preparation procedure, thus, a mass of 50 mg was selected, ensuring a good signal-to-noise ratio while maintaining analytical linearity. Fractional factorial design and Doehlert design were employed to optimize the experimental conditions, including the evaluation of the acidic medium, sonication time, and the use of a surfactant (Triton X-100). Experimental optimization indicated that the use of 1.25 mol L-1 HNO3, without surfactant addition, and a sonication time of 30 min resulted in the best analytical performance. The analytical method presented limits of quantification (LoQ) ranging from 3.03 to 81.6 mg kg-1. Accuracy was confirmed by the chemical analysis of certified reference materials (CRM) of fly ash (BCR 176R) and road dust (BCR 723), with agreement values ranging from 88.0 (± 0.6) to 91.8 (± 0.1)%. Precision was expressed as relative standard deviation (%RSD), with values below 5% (n = 3). The methodology enabled the analysis of urban dust with reduced reagent consumption and simplified sample preparation, supporting its applicability in environmental studies. In the second part, the direct determination of Hg was applied to 21 urban dust samples collected in the municipality of Santo Amaro, Bahia, using thermal decomposition and detection by atomic absorption spectrometry (AAS). The limits of detection (LoD) and quantification (LoQ) obtained were 0.08 ng g-1 and 0.25 ng g-1, respectively. Method accuracy was confirmed by the chemical analysis of a CRM for trace elements in multi-nutrient fertilizer (NIST 695), with an agreement of 106.3 (± 5.2)%. The %RSD value was below 5%. The analytical method allowed the quantification of Hg over a wide concentration range, revealing a heterogeneous spatial distribution, as well as good accuracy and precision. Hg concentrations ranged from 15.8 (± 0.3) ng g-1 to 1198 (± 29) ng g-1, with a mean of 54.9 (± 32.6) ng g-1 and a median of 46.1 ng g-1, after application of the Shapiro–Wilk (SW–W) normality test. The highest concentrations were observed in areas with greater urbanization, intense vehicular traffic, and proximity to industrial sites. Environmental interpretation was performed using the enrichment factor (EF), geoaccumulation index (Igeo), and ecological risk indices (Er), calculated based on a regional geochemical background specific to the state of Bahia. The results indicated significant enrichment and elevated ecological risk at localized points, with a very high potential ecological risk for the study area, considering the specific sampling period and the prevailing climatic conditions at that time. The sustainability of the analytical methods for the sequential determination of Cd, Cu, Mn, and Pb using suspension preparation and for the direct determination of Hg was evaluated using the AGREE (Analytical Greenness Metric) index, yielding scores of 0.78 and 0.86, respectively, indicating high adherence to the principles of Green Analytical Chemistry. Overall, the results demonstrate that the applied analytical methods are feasible, reliable, and suitable for the environmental monitoring of trace metals in urban dust. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Dissertação 2026-03-06T00:00:00Z 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 2026-04-10T00:00:00Z https://repositorio.ufba.br/handle/ri/44270 Título: Avaliação da composição mineral de material particulado atmosférico coletado na região geográfica intermediária de Salvador e de Amélia Rodrigues, Bahia, Brasil Autor(es): Sacramento, Carlos Leandro Cruz Primeiro Orientador: Araujo, Rennan Geovanny Oliveira Abstract: Air pollution has been a major focus of study in the scientific community, aiming to understand its implications for human health, ecosystems, and material heritage, identifying itself as a key element in the pursuit of sustainable development. The accelerated growth of urban areas, driven by industrialization and population increase, has significantly contributed to the current scenario. In this context, the present work aims to investigate, evaluate, and quantify samples of atmospheric particulate matter in the form of total suspended particles (TSP) and respirable particles (PM₂,₅), according to the limits established by Resolution No. 491/2018 of the National Environment Council (CONAMA), in addition to chemically characterizing the mineral composition. Sampling was conducted in the Intermediate Geographic Region of Salvador, encompassing the municipalities of Lauro de Freitas, Madre de Deus, São Sebastião do Passé, São Francisco do Conde, and Amélia Rodrigues, in the Metropolitan Region of Feira de Santana, in August, September, and December 2021, covering both the dry and rainy seasons in the region. Collections occurred during nominal 24-hour periods, using three portable samplers (HANDI-VOL) for PTS and one portable prototype for PM₂,₅, operating simultaneously. The geometric mean concentrations of PTS and PM₂,₅ were below the limits established by Resolution No. 491/2018 of the CONAMA. After the sampling procedures, the particulate matter deposited on the filters was subjected to acid extraction, followed by chemical analysis by inductively coupled plasma optical emission spectrometry (ICP OES) to determine Al, Ba, Cr, Cu, Fe, Ni, Mn, Mo, Pb, Sb, V, and Zn. Based on the results obtained, the trace metals were grouped in ascending order of concentration (Mo < V < Sb < Pb < Ni < Mn < Zn < Ba < Cr < Al < Cu < Fe) for PTS. The concentrations of the chemical elements in the PM2.5 samples were below the quantification limit of the analytical method. With the predominance of Fe concentration in the chemical composition of the atmospheric particulate matter (PTS), the results obtained clearly showed that in the study region, the chemical composition of atmospheric particulate matter is strongly associated with natural sources, but is directly influenced by anthropogenic sources such as the use of fossil fuels, vehicular traffic associated with brake system wear, maritime traffic, industrial, petrochemical and port activities through the presence of Cu, Mn, Pb, Sb and Zn. An investigation of pollution indices was carried out using the enrichment factor (EF) and the geoaccumulation index (Igeo), as geochemical indices, highlighting the need for extra attention to the concentrations of Cu, Cr and Sb. Multivariate data analysis was crucial in determining a possible anthropogenic contribution in the region. Principal component analysis (PCA) showed that Fe was the chemical element with the greatest contribution to the chemical composition of the PTS, mainly associated with natural sources, such as soil resuspension. Meanwhile, the concentration of Cu, Fe, Mn, and Pb indicated anthropogenic influence from traffic and industrial activities. During the dry and rainy seasons, PCA showed variation in the relative weight of the metals, but maintained the distinction between natural and anthropogenic sources. Hierarchical cluster analysis (HCA) consistently grouped the samples, separating sets influenced by industrial/port activities from those of natural origin. This analysis confirmed the correlation between Cu, Mn, and Sb as markers of anthropogenic impact. Together, PCA and HCA reinforced the identification of the main emission sources in the studied region. Finally, this work may assist the corresponding agencies in more effective air quality monitoring in the region. Editora / Evento / Instituição: Universidade Federal da Bahia Tipo: Dissertação 2025-09-30T00:00:00Z