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The synthesis and characterization of a novel titania/silica hybrid xerogel subsequently modified with 4-methylpyridine (4-Pic), named TiSi4Pic+Cl- is reported. The physicochemical, structural and thermal properties of TiSi4Pic+Cl- were characterized using several techniques. Anchoring cobalt(II) phthalocyanine (CoTsPc) in TiSi4Pic+Cl- showed greater electroanalytical sensitivity over other sensors built with these materials. A novel electroanalytical method was developed to quantify the noxious biocide pentachlorophenol (PCP) for environmental monitoring. The peak current intensity increased linearly with the analyte concentration in the range between 0.99 and 4.21 µmol L-1, based on the oxidation process (at + 0.81 V, vs. Ag/AgCl) of differential pulse voltammetry (DPV). The estimated limit of detection (LOD) was 29 nmol L-1. Recovery tests in environmental samples showed a PCP concentration of 2.05 ± 0.03 µmol L-1 (n = 3). The method was statistically validated by comparing the PCP concentrations with those obtained by molecular absorption spectrometry and high-performance liquid chromatography-diode array detection (HPLC-DAD). At a 95% confidence level, no difference between the results was found, therefore confirming the excellent accuracy of the proposed method.

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This study proposes a simple and effective method for determination of Al, Cd, Cu, Ni, and Zn in soil samples, associating ultrasound-assisted extraction and flame atomic absorption spectrometry (FAAS). Ultrasound-assisted extraction conditions were optimized using a central composite design. This method required small volumes of HCl, HNO3, and HF as an extraction solvent blend to ensure effective analyte extraction. Limits of detection and quantification were determined to assess the minimum accurate concentration of the studied elements that can be detected and quantified in a soil sample. Therefore, the ultrasound-assisted extraction was concluded as a simple and straightforward pretreatment technique to determine Al, Cd, Cu, Ni, and Zn concentrations in soil samples. Eight sites of agricultural and native forest areas of the city of Ponta Grossa and Guarapuava, State of Paraná, Brazil, were evaluated for metals, and compared with the reference values for trace elements provided by the Brazilian National Environment Council. Environmental assessment of soils from those eight sites was accomplished through Igeo, EF, CF, and PLI parameters, which aimed at the evaluation of agricultural sites in comparison with adjacent natural forest sites with no history of anthropogenic mobilization to determine the degree of the contribution of anthropogenic sources to metal concentrations. According to the Igeo, EF, and CF parameters, all sites were classified as unpolluted to moderately polluted and none or minor enrichment due to anthropogenic activities were noticed. PLI parameter evaluated the concentration of all studied metals in soils to stipulate an order of contamination, which was concluded as site 8

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Abstract This study describes the use of bentonite in suspension for the caffeine adsorption (pollutant of emerging concern) by taking different conditions of the pH, adsorbent mass, adsorbent calcination temperature and interferents into account. The results were compared with those obtained using bentonite immobilized in alginate beads. The acid medium has a greater efficiency for the caffeine adsorption and the adsorbent calcination temperature exerts, due to structural changes. Caffeine removal higher than 90% was obtained at optimized conditions. The Langmuir model indicated a better fit of the data and the adsorption capacity of caffeine onto bentonite. The bentonite immobilized led to a slower adsorption process in relation to the suspended.

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In this work, different chemometric tools were compared to classify n = 26 conventional (CONV) and n = 19 organic (ORG) coffees from the main Brazilian producing regions based on the chemical composition, physicochemical properties, and antioxidant activity. Principal component analysis separated ORG and CONV coffees but the distinction among the producing regions of Brazilian coffee was not possible. Partial least squares discriminant analysis classified all ORG and CONV coffees in the external validation. Similarly, linear discriminant analysis was able to discriminate 100% and 81% of ORG and CONV coffees in the external validation, respectively, in which total phenolic content (TPC), ferric reducing antioxidant activity, and caffeic acid were the main discriminant variables. Overall 100% of samples from Paraná, Minas Gerais, and blended samples were correctly classified, where TPC, flavonoids, inhibition of lipid peroxidation, caffeic acid, pH, and soluble solids were the main discriminant variables. Support vector machines classified 95% ORG and 88% CONV, 100% Coffea arabica, and 88% and 78% coffees produced in São Paulo and Minas Gerais. k-Nearest neighbors was effective in distinguishing 100% CONV, 89% ORG, 100% coffees from São Paulo, and 100% C. arabica coffees. Overall, HPLC data and simple physicochemical parameters allied to chemometrics were effective in authenticating the cultivation system and the botanical origin of Brazilian coffees. PRACTICAL APPLICATION: Coffee adulteration is a serious problem in the food chain as some fraudsters replace coffee powder by other cheaper products. In the case of organic coffee, this scenario is even worse as still there is not a universal method to differentiate conventionally grown coffee from its organic counterpart. In addition, Brazilian coffee is produced in different regions and the commercial value varies. Therefore, we analyzed some physicochemical, chemical, and antioxidant properties of Brazilian coffees from distinct origins and classified the samples using chemometrics. Our approach seems to be interesting for quality control purposes.

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Vegetable oils used in frying food represent a social problem as its destination. The residual oil can be recycled and returned to the production line, as biodiesel, as soap, or as putty. The state of the residual oil is determined according to their physicochemical characteristics whose values define its economically viable destination. However, the physicochemical analysis requires high costs, time and general cost of transporting. This study presents the use of a capacitive sensor and a quick and inexpensive method to correlate the physicochemical variables to the dielectric constant of the material undergoing oil samples to thermal cycling. The proposed method allows reducing costs in the characterization of residual oil and the reduction in analysis time. In addition, the method allows an assessment of the quality of the vegetable oil during use. The experimental results show the increasing of the dielectric constant with the temperature, which facilitates measurement and classification of the dielectric constant at considerably higher temperatures. The results also confirm a definitive degradation in used oil and a correlation between the dielectric constant of the sample with the results of the physicochemical analysis (iodine value, acid value, viscosity and refractive index).