http://repositorio.ufc.br/handle/riufc/29279 Sun, 26 Jul 2026 23:00:58 GMT 2026-07-26T23:00:58Z http://repositorio.ufc.br/handle/riufc/87186 Título: Validação metrológica de método por ICPOES em matriz de fígado bovino: uma abordagem segundo as diretrizes do INMETRO Autor(es): Ferreira, Felipe Souza Abstract: Chemical measurements are essential for ensuring the reliability of analytical results used in food quality control and environmental monitoring. In this study, the analytical figures of merit for Se, Co and Sr were evaluated according to the INMETRO DOQ-CGCRE-008 guideline using the reference material RM-Agro E3001a (bovine liver). These elements were selected because they were determined during an interlaboratory study conducted for the consensus characterization of the reference material using external calibration, in which unsatisfactory analytical performance was observed. Therefore, a validation study based on the standard addition method was carried out to minimize matrix effects and improve analytical reliability. Samples (250 mg) were digested by microwave-assisted acid digestion and analyzed by ICP-OES. Three replicate standard-addition calibration curves were combined into a single calibration curve for each analyte, increasing the degrees of freedom of the regression and providing a more robust statistical basis for method validation. Matrix effects were confirmed for all analytes, demonstrating the inadequacy of external calibration. The Cochran test indicated heteroscedasticity in the combined calibration data, requiring weighted least-squares regression, while ANOVA confirmed the statistical significance of the weighted models. Among the investigated analytes, Sr showed the best analytical performance, with LOD and LOQ of 0.5 and 1.5 μg kg⁻¹, respectively, quantitative recovery (100%) and normalized error (En ≤ 1), indicating excellent agreement with the certified reference value. Co also showed satisfactory performance, with LOD of 9.1 μg kg⁻¹, LOQ of 27.5 μg kg⁻¹, recovery of 111% and En ≤ 1. Although the recovery slightly exceeded the nominal value, the result remained metrologically acceptable according to the INMETRO validation criteria. In contrast, Se presented the poorest performance, with LOD (195.6 μg kg⁻¹) and LOQ (593 μg kg⁻¹) close to the certified concentration of the reference material. In addition, residual carbon remaining after digestion caused translational spectral interference, leading to systematic overestimation of the analyte concentration and an average recovery of 132%, compromising the method accuracy. The uncertainty budget showed that sample weighing and the analytical regression were the dominant contributors to the combined uncertainty, whereas volumetric operations had a comparatively smaller contribution. This result highlights the importance of properly modelling the calibration step and propagating uncertainty through the analytical measurement equation, particularly for methods based on standard addition. Overall, the proposed methodology fulfilled the validation requirements established by INMETRO for Co and Sr and demonstrated that the integration of standard addition calibration, weighted regression, uncertainty estimation and metrological traceability provides greater confidence and technical defensibility for analytical results. The study also emphasizes that evaluating uncertainty together with the conventional validation parameters is essential for supporting reliable decision-making in chemical measurements. Tipo: TCC Thu, 01 Jan 2026 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/87186 2026-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/85082 Título: Glicoaldeído no meio interestelar: proposta de mecanismo químico de formação e análise teórica acerca de sua viabilidade termodinâmica Autor(es): Mattos, Samuel Sousa Abstract: Astrochemistry is a scientific field that stands out for the identification and study of chemical processes in the interstellar medium (ISM), with one of its main objects of study being complex organic molecules, which are generally associated with biomolecule synthesis processes. With this in mind, glycolaldehyde (GA) becomes the focus of this work due to its possible connections to reaction processes associated with prebiotic chemistry. Furthermore, the precursor used for a possible route to the synthesis of GA was ethanol, an alcohol already detected in the ISM and with a possible abundance correlation with GA itself. Thus, a four-step reaction mechanism was proposed, and the energetic feasibility of the proposal was analyzed through thermodynamic parameters of the reactions. These data were obtained using the theoretical methods DFT and CCSD(T), based on the M06-2X functional and the aug-cc-pVTZ basis set. The combined level of theory was denoted as CCSD(T)//M06-2X/cc-pVTZ. Based on this level of theory, several types of calculations were performed in order to obtain thermodynamic parameters for the system. The combined level of theory demonstrated superiority in the results, given the effectiveness of CCSD(T) for systems involving weakly localized radicals. Thus, based on the analysis of the thermodynamic data, steps 1, 2.1, and 4 exhibited considerable energy barriers along with an endothermic character for the reactions, while step 3, in addition to being exothermic, maintained a lower barrier than the other steps. Furthermore, step 2 did not yield results due to the inefficacy of the optimizations of the proposed stationary states. Therefore, in view of the thermodynamic data, the considered mechanism, and the extreme conditions employed, the theoretical analysis of the synthesis of glycolaldehyde from ethanol resulted in the infeasibility of the process. Tipo: TCC Thu, 01 Jan 2026 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/85082 2026-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/85081 Título: Avaliação do desempenho do formato de 2-hidroxietilamônio como inibidor de corrosão acelerada por escoamento (FAC) em aço carbono Autor(es): Sousa, Samile Karen de Oliveira Abstract: Flow-Accelerated Corrosion (FAC) represents a critical challenge for the integrity of carbon steel pipelines in the oil and gas sector, with the application of corrosion inhibitors being one of the primary methods employed for its mitigation. This work evaluated the performance of the protic ionic liquid (PIL) 2-hydroxyethylammonium formate as an inhibitor for 1020 carbon steel in a saline medium, consisting of a 3.5% NaCl solution under continuous flow. For the experiments, a closed-loop system (flow loop) with one-inch PVC piping was used, operating at a flow rate of 650 L/h. Tests were conducted at temperatures of 25, 35, 45, and 55 °C, at intervals of 4, 8, and 12 h. The inhibitor's efficiency at a concentration of 500 ppm and the assessment of surface wear were investigated through gravimetric techniques and Computational Fluid Dynamics (CFD), complemented by optical microscopy (OM) and X- ray diffraction (XRD). The system's hydrodynamics proved to be a determinant factor in the degradation rate; CFD simulations indicated that samples subjected to parallel flow experienced higher shear stresses, accelerating both mechanical and chemical wear. The inhibitor showed low resistance to shear stress at ambient temperatures, with efficiencies lower than those reported in static regimes. The best efficiency, 70.14%, was achieved at 45 °C, possibly due to a transition in the adsorption mechanism from physical to chemical, making the protective film more robust. XRD analysis identified lepidocrocite as the majority phase and evidenced that the inhibitor favored the formation of goethite, a more stable corrosion product. It is concluded that, although 2-hydroxyethylammonium formate demonstrates protective potential, its effectiveness under constant flow is highly dependent on temperature and the stability of the film formed, reinforcing the need for operational condition optimization to enable its use in dynamic industrial systems. Tipo: TCC Thu, 01 Jan 2026 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/85081 2026-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/85080 Título: A influência da adição de cobre no processo corrosivo do aço duplex 2205 Autor(es): Monteiro, Rayssa Gabrielly Freitas Abstract: This study aimed to evaluate the influence of different copper contents on the corrosion behavior of duplex stainless steel 2205 when exposed to sodium chloride–containing media under different pH conditions, since the literature indicates that the effect of copper on the corrosion resistance of this material does not exhibit a consistent trend as a function of its content. The analyzed samples consisted of duplex stainless steel 2205 without copper addition and with 2 wt.% and 4 wt.% Cu additions. The investigation was carried out at room temperature (25 °C) using electrochemical techniques, including open circuit potential (OCP) monitoring, linear potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS), as well as optical microscopy analyses for metallographic surface evaluation after the tests. The results indicated that decreasing pH increased the aggressiveness of the environment for all samples, promoting shifts in the potential toward more negative values and intensifying localized corrosion. The addition of 2 wt.% Cu proved to be beneficial, especially under more acidic conditions, showing higher electrochemical stability, more noble corrosion potential values, and higher impedance modulus at low frequencies, which are associated with increased stability of the passive film. In contrast, the sample containing 4 wt.% Cu did not show a proportional improvement in corrosion performance, suggesting that higher copper contents may compromise material stability. Overall, the study exhibited a qualitative and quantitative approach, allowing the establishment of relationships between copper content, medium acidity, and the corrosion behavior of duplex stainless steel 2205, providing technical support for the selection and application of this material in aggressive industrial environments. Tipo: TCC Thu, 01 Jan 2026 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/85080 2026-01-01T00:00:00Z