Banca de DEFESA: WELLINGTON DIEGO DA ASCENCAO

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : WELLINGTON DIEGO DA ASCENCAO
DATE: 15/12/2022
TIME: 14:00
LOCAL: Sala 307 do Bloco B do Campus de Santo André da Universidade Federal do ABC
TITLE:

CHEMOMETRIC STUDY OF THE REDUCTION REACTION OF NITRATE TO NITRITE BY METALLIC ZINC FOR QUANTIFICATION OF NITRATE IN WATER BY VISIBLE SPECTROPHOTOMETRY

PAGES: 82
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. The total experimental design was used to evaluate the influences of the variables and a central rotational composite design to arrive at the optimal point of efficiency of the reduction reaction from nitrate to nitrite. 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 0.024 mg L^-1 and 0.08 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, undergroud 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.

COMMITTEE MEMBERS:
Presidente - Interno ao Programa - 1864481 - HUEDER PAULO MOISES DE OLIVEIRA
Membro Titular - Examinador(a) Interno ao Programa - 3047441 - MONICA BENICIA MAMIAN LOPEZ
Membro Titular - Examinador(a) Externo ao Programa - 1544248 - JOSE CARLOS RODRIGUES SILVA
Membro Suplente - Examinador(a) Interno ao Programa - 1814655 - LUCIA HELENA GOMES COELHO
Membro Suplente - Examinador(a) Externo à Instituição - THAYS DE SOUZA LIMA