Browsing by Author "Melo, Nathalie Ferreira Silva de"

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    Nitrogen, phosphorous and potassium polymeric microparticles : application and validation of analytical methods for determination of a promising fertilizer.
    (2021) Chagas, Júnior Olair; Gomes, José Messias; Rodrigues, Júlia Helena Valadares; Cunha, Isabela Cristina de Matos; Melo, Nathalie Ferreira Silva de; Silva, Gilmare Antônia da; Lobo, Fabiana Aparecida
    Traditional analytical methods were applied to microparticles synthesized using a mixture of polymers. The microparticles containing nitrogen, phosphorus and potassium (NPK) were developed for application as a controlled release alternative to traditional fertilizers. Thus, analytical methods for the evaluation of nitrogen, phosphorus and potassium (essential nutrients for plants) in polymeric microparticles were applied andthe results validated for this kind of sample. The linearity of the methods was established in the range of 10 to 20 mg L-1 for N, 0 to 2 mg L-1 for P and 0 to 2.4 mg L-1for K. The relative standard deviation (RSD) of intermediate precision of the method was < 1% and recoveries from 99 to 108% for all nutrients were reached.The method proved to be selective, linear, precise and accurate for quantifying NPK in polymeric microparticles. In this way, it was possible to evaluate the correct nutrient encapsulation capacity inthe synthetized polymeric microparticles,which is of fundamental importance since this will directly interfere in the success of the intended fertilization process.
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    Poly(hydroxybutyrate-co-hydroxyvalerate) microspheres loaded with atrazine herbicide : screening of conditions for preparation, physico-chemical characterization, and in vitro release studies.
    (2011) Lobo, Fabiana Aparecida; Aguirre, Carina Levy de; Silva, Mariana Santos; Grillo, Renato; Melo, Nathalie Ferreira Silva de; Oliveira, Liliam Karla de; Morais, Leandro Cardoso de; Campos, Valquíria; Rosa, André Henrique; Fraceto, Leonardo Fernandes
    Due to their widespread use in agriculture as well as in urban areas, agricultural chemicals are globally some of the most commonly encountered substances in waters. The objective of this study is to develop (including preparation and characterization) a new modified release system for the herbicide atrazine, employing poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) microspheres. The microspheres were prepared by the emulsification/solvent evaporation method, emulsifying an organic phase (atrazine and PHBV dissolved in chloroform) into an aqueous phase containing polyvinyl alcohol (PVA) as surfactant, under stirring, and then evaporating the solvent. A 24-1 fractional factorial design, investigating the influence of four variables at two levels, was performed to obtain formulations with optimized association efficiencies. There was a greater dependence of association efficiency on PVA concentration (negative) and the mass of polymer (positive) with lesser influence of both stirring speed and organic phase volume. The size of the particles was assessed using scanning electron microscopy, which showed that the particles were rough-surfaced spheres. The results obtained are promising, since the formulations presented encapsulation efficiency near 25% and the release kinetics profile of atrazine was altered when it was encapsulated in the microparticles, indicating that these systems may be efficient in reducing the environmental impact caused by the herbicide, hence making it safer to use.
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    Polymeric microparticles for modified release of NPK in agricultural applications.
    (2018) Chagas, Júnior Olair; Gomes, José Messias; Cunha, Isabela Cristina de Matos; Melo, Nathalie Ferreira Silva de; Fraceto, Leonardo Fernandes; Silva, Gilmare Antônia da; Lobo, Fabiana Aparecida
    The aim of this work was to synthesize polymeric microparticles as carriers for nitrogen, phosphorus, and potassium (NPK fertilizer) for agricultural applications, using polyglycerol (PG) to improve the synthesis procedure. Multivariate experimental designs were employed to obtain a satisfactory synthesis. The desirability function identified the best conditions for preparation of the microparticles as being 100.00 mg of poly(e-caprolactone) (PCL), 825.00 mg of PG, 9.25 mL of chloroform, and 0.9% w/v of polyvinyl alcohol (PVA). This resulted in average encapsulation rates of 94.23% for N, 99.80% for P, and 65.00% for K. The profile of release from the microparticles was according to diffusion following Fick’s Law. These observations confirmed the capacity of the proposed microparticles to sustain a continuous and prolonged release of NPK for the purpose of plant fertilization.