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Determinação do teor de biodiesel metílico de palmiste (BMPALM) e pinhão manso (BMPM) usando espectroscopia no infravermelho médio e calibração multivariada por resolução multivariada de curvas com mínimos quadrados alternados (MCR-ALS) e regressão por vetor de suporte (SVR)

2026-02-06T06:27:00Z

Title: Determinação do teor de biodiesel metílico de palmiste (BMPALM) e pinhão manso (BMPM) usando espectroscopia no infravermelho médio e calibração multivariada por resolução multivariada de curvas com mínimos quadrados alternados (MCR-ALS) e regressão por vetor de suporte (SVR) Abstract: The growing demand for biodiesel has increased the risk of marketing fuels that do not meet the standards established by the Brazilian National Agency of Petroleum, Natural Gas and Biofuels (ANP), with the concentration of biodiesel in diesel blends being one of the main parameters of non-compliance. In response to this analytical demand, this study developed methods for quantifying the content of palm kernel methyl biodiesel (BMPALM) and jatropha methyl biodiesel (BMPM) in diesel blends, using mid-infrared (MIR) spectroscopy combined with multivariate calibration techniques: multivariate curve resolution with alternating least squares (MCR-ALS), support vector regression (SVR), and partial least squares (PLS) as the reference method. Samples were prepared in different concentrations (1.00 to 30.00% v/v), submitted to spectral acquisition, and then modeled using chemometric approaches. The models built for each type of biodiesel showed good accuracy, with low root mean square errors (RMSEs < 1%) in all stages (calibration, cross-validation, and prediction), and good linearity, as evidenced by determination coefficients (R²) very close to 1. Statistical tests (F-test) indicated similar variances between most models, with few exceptions in specific comparisons between techniques. The results confirm that the combination of FT-MIR spectroscopy with advanced multivariate calibration methods, especially SVR and MCR-ALS, enables reliable quantification of BMPALM and BMPM in diesel blends. Moreover, these two methods offer advantages over PLS, such as lower sample requirements for model construction and reduced operational costs, representing promising alternatives for quality control in the fuel industry and for regulatory monitoring.

Plataformas eletroquímicas de baixo custo produzidas em laboratório para a determinação de antibióticos em matrizes farmacêuticas, alimentares e ambientais

2026-02-03T06:23:25Z

Title: Plataformas eletroquímicas de baixo custo produzidas em laboratório para a determinação de antibióticos em matrizes farmacêuticas, alimentares e ambientais Abstract: The development and application of simple, rapid, and low-cost electroanalytical platforms are essential for the determination of antibiotics in various sample matrices. In this study, three distinct approaches were proposed and evaluated for the quantification of antibiotics in pharmaceutical, food, and environmental samples, focusing on strategies that combine selectivity, sensitivity, and operational feasibility. In pharmaceutical analysis, the batch injection analysis with amperometric detection (BIA-AD) technique was employed using a boron-doped diamond (BDD) electrode for the sequential determination of amoxicillin (AMX) and potassium clavulanate (CLA). The analytical strategy involved the application of two sequential potential pulses (+1.3 V and +1.8 V), enabling selective quantification of AMX at +1.3 V and oxidation of both (AMX + CLA) at +1.8 V. The oxidation current of CLA was obtained by subtraction, using a correction factor. The method showed high analytical throughput (>200 injections/hour), excellent precision (RSD < 1.3%), and detection limits of 0.31 μmol·L⁻¹ for AMX and 1.99 μmol·L⁻¹ for CLA. In food analysis, a disposable electrode composed of graphite, glass varnish, and acetone was developed for the detection of sulfamethoxazole (SMX) in milk. Selectivity and stability were enhanced by using two detection potential pulses (+1.0 V and +1.3 V) and two cleaning potential pulses (+1.5 V and −1.5 V). The method showed good linearity (1.0–50.0 μmol·L⁻¹), a detection limit of 0.31 μmol·L⁻¹, and recoveries of 68 ± 7%, 103 ± 7%, and 115 ± 7% for milk samples fortified with 5.0, 10.0, and 20.0 μmol·L⁻¹ of SMX, respectively. For environmental monitoring, a voltammetric approach was developed for the indirect detection of AMX in water using disposable sensors fabricated by additive manufacturing (3D printing). The strategy involved three sequential steps: (i) chemical and electrochemical activation of the 3D electrode in alkaline medium, (ii) preconcentration of AMX by adsorption onto the electrode surface, and (iii) detection via oxidation of adsorbed AMX, followed by reduction and reoxidation of the oxidized product (quinone). The differential pulse voltammetry (DPV) technique enabled a detection limit of 0.01 μmol·L⁻¹, with high selectivity against evaluated interferents and recoveries ranging from 82 to 106% in different water types. All three approaches demonstrated robust analytical performance, operational simplicity, low cost, and strong potential for portability, highlighting the effectiveness of electrochemical platforms as tools for routine applications in quality control, food safety, and environmental surveillance.

Estudo químico e avaliação da citotoxicidade do extrato etanólico e frações de Cereus jamacaru DC. (Cactaceae)

2025-11-20T06:19:32Z

Title: Estudo químico e avaliação da citotoxicidade do extrato etanólico e frações de Cereus jamacaru DC. (Cactaceae) Abstract: This study evaluated the cytotoxic potential of the ethanolic extract from Cereus jamacaru cladodes and its fractions against the HCT-116 (colorectal carcinoma) cell line, correlating bioactivity with the chemical profile obtained by chromatography and mass spectrometry. The extract was partitioned into hexane, dichloromethane, ethyl acetate, and hydromethanolic phase, with similar yields among the organic fractions and predominance of the polar phase. Cytotoxicity was determined using the MTT assay, with an initial screening at 50 and 5 µg/mL and IC50 determination for the active samples. Chemical characterization employed UHPLC–ESI–MS/MS for low-volatility/thermolabile compounds and GC–EI–MS (70 eV) for volatile and semi-volatile ones. Molecular networks (GNPS) were generated with cosine ≥ 0.7 and ≥ 6 matched peaks and visualized in Cytoscape. In screening at 50 µg/mL, FHC showed the highest inhibition (88.59 ± 10.88%), followed by the ethanolic extract (59.17 ± 4.17%) and FDC (65.91 ± 14.03%), while FAC was less active (38.29 ± 7.41%). As a positive control, doxorubicin (DOX) showed inhibition of 88.95 ± 0.76%. Subfractionation maintained high performance (≥ 75% inhibition in 16 FHC subfractions and 10 FDC subfractions). The IC50 values confirmed the greater potency for FHC (41.30 µg/mL) and FDC (46.61 µg/mL), with emphasis on the subfractions of FHC (≈43–58 µg/mL) and FD-3 (39.02 µg/mL). Fatty acids and their derivatives were mostly annotated, such as lauric acid, palmitic acid, ethyl palmitate, methyl linoleate, and phytol, which is consistent with the greater effect of the less polar fractions. Analyses in ESI+ and ESI– showed preferential detection of neutral lipids and terpenoids in the positive mode, and of more polar and acidic compounds in the negative mode. The results indicate that Cereus jamacaru is a promising source of cytotoxic metabolites against HCT-116, with emphasis on apolar fractions, and that the integration between UHPLC–ESI–MS/MS and GC–EI–MS, associated with GNPS networks, allowed linking chemical class (fatty acid derivatives, esters, and terpenoids) to bioactivity, providing a robust framework for future studies of isolation, structural elucidation, and investigation of mechanisms of action.

Impressão 3D aplicada à eletroanálise: manufatura de célula eletroquímica, filamento condutor e aplicação no meio ambiente.

2025-10-11T06:27:04Z

Title: Impressão 3D aplicada à eletroanálise: manufatura de célula eletroquímica, filamento condutor e aplicação no meio ambiente. Abstract: In this work, we first present a novel disposable electrochemical cell designed for the analysis of small volumes (50 to 2000 µL). The cell consists of only two fully 3D-printed components, allowing for easy integration of various materials as the working, reference, and auxiliary electrodes. As a proof of concept, paracetamol, cocaine, and uric acid were used as model analytes, with different materials employed as the working electrode. Linear calibration curves (R2 > 0.99) with similar slopes (0.29 ± 0.01 μA μmol L⁻¹; RSD = 3.4%) were obtained using square wave voltammetry for different volumes of paracetamol standard solutions (50, 100, and 200 μL). For uric acid, a linear range of 10–125 μmol L⁻¹ (R2 > 0.99) was achieved using differential pulse voltammetry and a laser-induced graphene-based electrode as the working electrode. When a boron-doped diamond working electrode was used, successful screening tests were conducted on cocaine samples, enabling selective detection of cocaine in the presence of common adulterants, with a recovery rate of 103 ± 4%. In the second part of the study, we proposed the development of a filament with a high conductive load while maintaining good printability. The composition studied consisted of carbon black as the conductive material and polypropylene as the thermoplastic. A filament with a composition of 40% carbon black and 60% polypropylene was obtained. Using square-wave voltammetry, using electrodes printed from this filament as the working electrode, colchicine was determined in tap, bottle, and river water samples. The analytical method showed a linear response range between 2 and 50 µmol L-1, an LD of 10 nmol L-1, and recoveries above 90%, while the preconcentration method showed a factor of 130.