Banca de QUALIFICAÇÃO: WELLINGTON DIEGO DA ASCENCAO

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
STUDENT : WELLINGTON DIEGO DA ASCENCAO
DATE: 19/10/2022
TIME: 14:00
LOCAL: Sala 406 do Bloco B do Campus de Santo André da Universidade Federal do ABC
TITLE:

OPTIMIZATION OF THE NITRATE TO NITRITE REDUCTION REACTION BY METALLIC ZINC USING EXPERIMENTAL MULTIVARIATE FACTORAL PLANNING FOR QUANTIFICATION OF NITRATE BY SPECTROPHOTOMETRY IN THE VISIBLE

PAGES: 20
BIG AREA: Ciências Exatas e da Terra
AREA: Química
SUMMARY:

Nitrate and nitrite are nitrogen compounds whose quantification in water is of paramount importance for the environment and human health. High concentrations of these compounds in water come from anthropic actions in the environment and are related to the occurrence of cancer in humans. Determining the concentration of nitrate in aqueous solutions is not a trivial task, and several analytical methods are already available. However, the limits of detection of nitrate concentration in these methods are restricted and sensitive to interference. Furthermore, the use of cadmium as a reducing agent in some quantifications is not ecologically correct. In this work, a new approach was developed for the quantification of nitrate in water, even at lower concentrations, by indirect UV-VIS spectrophotometry. Nitrate is reduced to nitrite with granulated metallic zinc, in a buffered medium with acetate/acetic acid buffer solution, and nitrite is quantified by visible spectrophotometry using the Griess reaction using the sulfanilamide method and N-(1-naphthyl)-ethylenediamine. Experimental design by central rotational composite design was used to reach the optimal point of efficiency of the nitrate to nitrite reduction reaction. The influence of pH, constitution and concentration of the buffer solution, zinc mass and granulometry and stirring time on the efficiency of nitrite generation was evaluated. The ideal conditions were: acetate-acetic acid buffer solution with concentration and pH, respectively, 0 80 mol L^-1 and 6.10; size and mass of zinc particles, in that order, 20 MESH, 300 mg zinc. LOD and LOQ were equal to 0.044 mg L^-1 and 0.16 mg L^-1, respectively. The method showed excellent accuracy and precision to quantify nitrate in samples of bottled mineral water, river water, sea water, supply water and effluents, replacing cadmium with zinc, a more ecological reagent. Furthermore, the method showed lower LOD and LOQ than traditional methods based on visible spectrophotometry.

BANKING MEMBERS:
Presidente - Interno ao Programa - 1864481 - HUEDER PAULO MOISES DE OLIVEIRA
Membro Titular - Examinador(a) Interno ao Programa - 2145401 - DIOGO LIBRANDI DA ROCHA
Membro Titular - Examinador(a) Externo ao Programa - 1909336 - ALEXANDRE ZATKOVSKIS CARVALHO
Membro Suplente - Examinador(a) Externo ao Programa - 1544248 - JOSE CARLOS RODRIGUES SILVA
Membro Suplente - Examinador(a) Externo à Instituição - THAYS DE SOUZA LIMA