Banca de QUALIFICAÇÃO: GIORGIO LÚCIO FERNANDES

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : GIORGIO LÚCIO FERNANDES
DATE: 15/07/2021
TIME: 09:00
LOCAL: Remotamente pelo Google Meet
TITLE:

Construction of a multichannel UV-VIS spectrophotometer and applications in the study of chemical reaction kinetics: a proposal for an analytical and educational platform

KEY WORDS:

 UV-VIS spectrophotometer, Multichannel spectrophotometry, CMOS, Digital image acquisition, chemical kinetics.

PAGES: 84
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUBÁREA: Química Analítica
SPECIALTY: Instrumentação Analítica
SUMMARY:

: The UV-VIS spectrophotometer is the most widely used analytical instrument in analytical laboratories around the world. Due to the recurrent lack of investment in Brazilian education, it is still possible to observe a great lack of infrastructure in teaching laboratories. As an alternative to the acquisition of these commercial equipment, the present work presents the construction and validation of a portable, low cost and light multichannel UV-VIS spectrophotometer. The instrument has the construction scheme of a single-beam spectrophotometer, using a CMOS (Complementary metal-oxide-semiconductor) camera as a multi-channel detector, a 1000 lines/mm holographic diffraction grating and a thermostated cell for the sample. innovative component compared to commercial instruments. The assembled device cost approximately $95.00, its dimensions were 23cmx13cmx06cm, providing easier accommodation and transport. For validation, a potassium permanganate solution was used as a chemical species due to its characteristic absorption spectrum. Thus, calibration tests and analytical validation of the equipment were performed by constructing an analytical curve with concentration solutions from 2.5x10^-5 to 2.0x10^-4 mol/L. As results, figures of merit were obtained: linear correlation coefficient (R2) 0.997, detection limit 0.331 mg/L, quantification limit 1.10 mg/L, measurement dispersion of 1.7%, spectral resolution 0.14nm , acquisition speed of up to 120 spectra/s. In addition, the molar absorptivity for potassium permanganate of 2.554 x103 Lmol-1cm-1 was calculated, being consistent with values reported in the literature. The equipment was also used to monitor the kinetics of chemical reactions. The investigated reaction was the oxidation of sucrose by potassium permanganate in a basic medium, known as the “chemical chameleon”. From the results obtained, the linear behavior in the Arrhenius equation was observed between temperatures from 30°C to 40°C, calculating the kinetic parameters Ea=13,932.03 J; ∆H^# (308.15K) = 11,370.07 J; ∆S^# (308.15K) = -190.43 J; ∆G^# (308.15K) = 70,052.13 J. Therefore, the manufactured equipment shows itself as a promising miniaturized analytical platform, accessible and with performance and performance comparable to commercial equipment, in addition to showing itself as a good teaching tool due to its ability to work fundamental concepts of chemistry.

 

 UV-VIS spectrophotometer, Multichannel spectrophotometry, CMOS, Digital image acquisition, chemical kinetics.

 

BANKING MEMBERS:
Externo à Instituição - FERNANDO SILVA LOPES - USP
Externo ao Programa - 1199268 - JAILSON VIEIRA DE MELO
Presidente - 2413537 - POLLYANA SOUZA CASTRO
Interno - 1149328 - VALTER JOSE FERNANDES JUNIOR