Banca de QUALIFICAÇÃO: JHONNY FRANK SOUSA JOCA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : JHONNY FRANK SOUSA JOCA
DATA : 13/03/2020
HORA: 14:00
LOCAL: sala 306, 3º andar, Bloco B, Campus SA da Fundação Universidade Federal do ABC, localizada na Avenida dos Estados, 5001, Santa Terezinha, Santo André, SP
TÍTULO:

Production of a solid phase multielementary reference material for direct solid sampling analysis by LIBS

PÁGINAS: 25
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Analítica
ESPECIALIDADE: Métodos Óticos de Análise
RESUMO:

The use of reference materials offers to the analyst tools to check the traceability of measurements that, in the case of spectroanalytical techniques, correspond to the methods used to determine the elementary quantitative composition. Reference materials aren’t available for all matrices and in the context of direct solid sampling analysis, this unavailability is even more latent. Laser induced breakdown spectroscopy (LIBS) has been highlighted among the spectroanalytical techniques that allow solid sampling analysis, but calibration is your “Achilles’ heel”¹, which justifies producing a synthetic reference material for direct solid sampling analysis by LIBS. Two routes are proposed for preparing the synthetic reference material: a) by extracting the metals from an aqueous solution, using 1- (2-pyridylazo) -2-naphthol (PAN) as a complexing agent and melted paraffin wax as an extractant and b) by direct dispersion of a multi-element standard avaliable in mineral oil in beeswax. Extraction efficiency of Cd²⁺, Cr³⁺, Cu²⁺, Fe³⁺, Mn²⁺ e Zn²⁺ from a multielementary aqueous solution containing between 1.0 and 6.0 mg L^-1 of these ions, using 700 μL of melted paraffin wax containing 0.025 mol kg^-1 PAN as an extracting agent, was initially evaluated by the removal (in percentage) of these ions from the aqueous phase after extraction. Best results were obtained at pH 9 or 10, where the removal for all these elements exceeding 90%, starting from 10 mL of aqueous solution. The paraffin waxes obtained after extraction were separated and analyzed by LIBS, in the same operational conditions adopted by Papai et al² and, despite the pre-concentration factor estimated at 14-fold, no signals were effectively different from the analytical blank for the elements under study. The dispersion of the multi-element standard prepared in mineral oil in beeswax produced homogeneous and firm mixtures, thus enabling the detection of elements incorporated by LIBS. Initially, beeswax samples containing 32 mg kg^-1 of the elements present in the standard were prepared and analyzed by LIBS in the same operational conditions previously adopted and analytical signals were obtained for Al, B, Cd, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Si, Ti, V and Zn. Next, the operational parameters for beeswax analysis by LIBS were optimized and paraffin disks were prepared containing increasing concentrations of multielementar standard and in different levels of mineral oil, making it possible to obtain analytical curves between 10 and 150 mg kg^-1 for Al, B, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Si, Ti, V and Zn. It was also verified that the oil content present in the beeswax disks affects the slope and linearity of the analytical curves and the appearance of the craters (spots) produced by the laser. The detection limits calculated for the different elements allow the application in complex matrices, such as cosmetics and lubricating oils, which can be easily incorporated into beeswax and, in sequence, analyzed by LIBS.

MEMBROS DA BANCA:
Presidente - Interno ao Programa - 1543683 - IVANISE GAUBEUR
Membro Titular - Examinador(a) Externo à Instituição - PEDRO VITORIANO DE OLIVEIRA - USP
Membro Titular - Examinador(a) Externo à Instituição - FLAVIO DE OLIVEIRA LEME - UFABC
Membro Suplente - Examinador(a) Interno ao Programa - 1933328 - HELOISA FRANCA MALTEZ