Banca de DEFESA: ANA CLARA RODRIGUES DE MAGALHÃES

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : ANA CLARA RODRIGUES DE MAGALHÃES
DATA : 05/04/2019
HORA: 08:30
LOCAL: Instituto de Química
TÍTULO:

GAS REAGENTS PRODUCTION BY PERSULFATE THERMAL DECOMPOSITION  AND ITS EFFECTS ON EDIBLE VEGETABLE OILS SAMPLE PREPARATION 

PALAVRAS-CHAVES:

Sample preparation, persulfate, in-situ reagent generation, edible vegetable  oils.

PÁGINAS: 75
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Analítica
ESPECIALIDADE: Métodos Óticos de Análise
RESUMO:

Sample preparation step usually implies in high costs and time consumption, in despite of its important play holed in analytical results quality. In this sense, development of new sample preparation strategies that increase analytical throughput and provide more sensitive and accurate analytical methods has being a subject of interest. Thus, the present work aiming to develop a new sample preparation based on the production of in-situ reagents from ammonium persulfate decomposition irradiated by microwave in a closed system for the analysis of samples with high-unsaturated fat content. The decomposition parameters, concentration of HNO₃ (3.5 to 14.0 mol L^-1), decomposition temperature (150 to 210 °C) and decomposition time (23 to 40 min) were evaluated to ensure decomposition efficiency as well as higher in-situ reagent production rate. Therefore, 8 ml of HNO₃ were added to safflower oil samples (m ≈ 0.250 g) in presence or absence of auxiliary decomposition vial containing (NH₄)₂S₂O₈ solution (2.0 mol L^-1). Persulfate effects on digestion step were evaluated by comparison with procedures performed using only HNO₃ taking the dissolved carbon content as analytical response. The proposed method was applied to samples of edible oils from safflower, coconut, flaxseed and chia to elemental analysis. Decomposition optimum conditions with persulfate indirect application were set at 210 °C with irradiation time of 40 min and HNO₃ concentration equal to 7 mol L^-1. Reagents in-situ generation by persulfate thermal decomposition led to a greater sample solubilization and clearer digested in face of those obtained only using HNO₃. However, the chemical evidences obtained from final digested in both procedures indicated that byproduct gas produced by persulfate thermal decomposition did not act as auxiliary oxidizing reagents. Under optimum conditions, DOC levels were equal to 4.9±0.2 and 17.8±2.8% (m/m) in nitric/persulfate and nitric digested, respectively. In addition, a significant difference was observed in relation to the digested obtained when persulfate was applied directly to the sample (23.2 ± 2.3% m/m). The proposed method presented good accuracy with results in agreement with FDA reference Method (p = 0.05). In addition, good precision (RSD <10%, N= 7) was found, with wide linear ranges and good linearity (R²≥ 0.999) and LOD ranging from 0.03 to 5.7 mg kg^-1. The proposed method allowed the determination of Ca, Zn, Fe, Na, P, As, Cr, Mn, Ni, Pb, Se and Cd in edible oils by ICP OES and ICP-MS. However, it was verified systematic errors occurrence to Cu, for all evaluated oils, and Fe in safflower oil. Thus, (NH₄)₂S₂O₈ indirectly use has proved to be an alternative method to nutrients and contaminants determination in edible vegetable oil samples with good analytical productivity, accuracy and precision.

MEMBROS DA BANCA:
Presidente - 1190574 - RODOLFO DE MELO MAGALHAES SANTANA
Interno - 2721446 - DANIELE CRISTINA MUNIZ BATISTA DOS SANTOS
Interno - 1698441 - RENNAN GEOVANNY OLIVEIRA ARAUJO
Externo à Instituição - MADSON DE GODOI PEREIRA - UNEB
Externo à Instituição - MARIANGELA VIEIRA LOPES - UNEB