Banca de QUALIFICAÇÃO: SARA DOS SANTOS NASCIMENTO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : SARA DOS SANTOS NASCIMENTO
DATE: 29/10/2021
TIME: 14:00
LOCAL: Google Meet
TITLE:

Use of simonkolleite as a biocidal agent in active food packaging and development of an electrochemical method for glyphosate determination based on simonkolleite and dopamine.

KEY WORDS:

simonkolleite. glyphosate, electrochemical sensor, active packaging, simonkollite

PAGES: 94
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUMMARY:

Glyphosate (GLI) is a pesticide used around the world that has potential damage to health, its determination involves high cost. It is important not only the development of low-cost methods for its determination, but also the development of support strategies for organic agriculture that can reduce the consumption of pesticides, such as the use of antimicrobial active packaging, which prolongs the shelf life of food. The objective of this work is the development of an electrochemical sensor for GLI and the development of active food packaging. GLI does not present an electrochemical signal, aiming at indirect detection, its interaction with dopamine (DOPA) was evaluated by UV-vis spectrophotometry and electrochemical techniques, which used a glassy carbon electrode (GC) and this one modified with multiple-walled carbon nanotubes (GCMWCN), the best medium for analysis was evaluated (buffers: acetate pH=4.5; phosphate pH=7; borate pH=10). Aiming at system sensitivity, the use of simonkollite (SK) nanoparticles was analyzed, in addition to SK containing Ag: 0.1% and 1%. For the development of the active packaging, the polymer chitosan was used, analyzing the influence of the concentration of reagents on the film characteristics, using chitosan (0.75%; 1.0%; 1.5% m/m) and acetic acid (1 and 2%v/v). To obtain the active action, SK was used, through two different functionalization methods: addition of SK suspension during drying and addition of SK (5%m/m) solid in the gel with stirring until its dissolution. Using the first method, the best drying time for functionalization was evaluated: 10min, 2h, 4h, 6h and 24h and the concentration of SK (1%, 2%, 3%m/m) in the film, these materials were analyzed via analysis thermogravimetry and Fourier Transform Infrared Spectrophotometer (FTIR). Using the second functionalization method, the film obtained was characterized by Scanning Electron Microscopy (SEM), X-Ray Spectrometry (XRS), Raman Spectroscopy. Using this functionalization method, SK nanoparticles containing Ag: 5% and 10% were also used, these materials were characterized via FTIR. For the development of the GLI sensor, the use of DOPA proved to be viable, being proposed a mechanism for the interaction involved. The use of CV electrode showed transport of adsorptive mass, the modification with NTC being relevant, as the use of different pH ranges, the use of pH=7, showed greater sensitivity, becoming the best option among the ranges evaluated. The use of SK provided greater sensitivity to the system, while the use of SK containing Ag promoted a reduction in signal intensity, indicating that the use of SK is more interesting to the system. Regarding the active packaging, the film prepared using 1% chitosan (m/m) and acetic acid (2% v/v) showed better physical characteristics. Using the first functionalization method, the thermogravimetric analysis indicated that the functionalization after 4 h of drying and SK concentration 2% (m/m) presented better stability performance. This sample was submitted to FTIR characterization, however, due to the low concentration of SK in the film, it was not possible to identify the presence of bands related to its presence. Using the second method of functionalization, the film obtained was characterized via SEM which indicated sample homogeneity; XRS and Raman spectroscopy - which indicated the presence of elements of the composition of chitosan and SK in the sample. Films obtained using SK-5%Ag; SK-10%Ag, characterized via FTIR, showed evidence of interaction between Ag and chitosan regions. Given the above, the systems evaluated have the potential to meet the objectives of the work.

BANKING MEMBERS:
Interno - 1127609 - DIOGENES MENESES DOS SANTOS
Presidente - 426640 - FABIANE CAXICO DE ABREU GALDINO
Externa ao Programa - 2723870 - FABRICIA DA ROCHA FERREIRA
Externa ao Programa - 1121008 - SONIA SALGUEIRO MACHADO