Banca de QUALIFICAÇÃO: PATRICIA CRISTINA COSTA LADEIRA

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : PATRICIA CRISTINA COSTA LADEIRA
DATA : 25/07/2019
HORA: 09:30
LOCAL: sala 304, 3º andar, Bloco B, Campus SA da Fundação Universidade Federal do ABC, localizada na Avenida dos Estados, 5001, Santa Terezinha, Santo André, SP
TÍTULO:

Development of a rapid method for chemical speciation of mercury in foods using UHPLC-ICP-MS

PÁGINAS: 23
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Analítica
ESPECIALIDADE: Análise de Traços e Química Ambiental
RESUMO:

Mercury (Hg) occurs naturally in environment, including atmosphere, water, soil and bioaccumulated in plants and animals. Exposure and poisoning by Hg and its compounds are a worldwide preoccupation due to its biological effect,¹ so the development of analytical methodologies has an extreme importance, as for total quantification as for fractionation and speciation. In this work, a system for Hg²⁺ determination by cold vapor generation hyphenated to inductively coupled plasma mass spectrometry (CV-ICP-MS) was optimized, allowing its application in total Hg quantification and fractionation analysis. Based on study of Rodrigues et al. (2009)², a system was assembled with a peristaltic pump Marte MPV-500 for introduction of reagents through Tygon® tubes with 1.52 mm of intern diameter. The nebulizer argon (Ar) line of ICP-MS (Agilent 7900) was linked to the system and a chamber of gas/liquid separation replaced the nebulizer and spray chamber, being connected to the ICP torch. An online redox reaction occurred between Hg²⁺ and reducing agents (both introduced in a continuous flow) generating Hg⁰_(g), that was carried to the ICP-MS by the Ar flow while the aqueous phase was wasted. In ICP-MS, the isotope ²⁰²Hg was quantified for being the most abundant in nature and returning a higher sensitivity. The first step to apply the system was the optimization of Ar flow rate introducing Hg²⁺ 5.0 µg L^-1 (in HNO₃ 1.0 % v v^-1), HCl 4.0 % v v^-1 and NaBH₄ 0.4 % w v^-1 (in NaOH 0.1 % w v^-1) at 400 µL min^-1 each. Varying the Ar flow rate from 0.1 to 1.6 L min^-1, it was verified a higher sensitivity with 1.2 L min^-1. After this, the best concentration of sodium borohydride (NaBH₄) and tin (II) chloride (SnCl₂), applied as reducing agents, were investigated introducing Hg²⁺ 2.0 µg L^-1 (in acid medium) and the reducing agent in study at 600 µL min^-1 each. Concentration of NaBH₄ (in NaOH, from 0.05 to 0.15 % w v^-1) was varied from 0.2 to 0.6 % w v^-1 and the best results were got with 0.5 % w v^-1. In its turn, SnCl₂ (in HCl 10 % v v^-1) concentration was varied from 0.2 to 1.4 % w v^-1, and the best condition was obtained for 0.8 % w v^-1. Knowing the best experimental conditions for Hg quantification by CV-ICP-MS, analytical parameters were determined for each reducing agent and for determination by ICP-MS. The best results were obtained applying SnCl₂, presenting an enrichment factor in sensitivity equal to 21 when compared to ICP-MS determinations, limits of detection and quantification equals to 9 and 29 ng L^-1, respectively, and RSD inferior to 2,0%. The accuracy was investigated by determination of total Hg in LOAM SOIL ERM® - CC141 and FISH MUSCLE ERM® - BB422, both from European Reference Materials, after digestion in closed microwave system equipped with PTFE vessels, model Ethos Easy from Milestone Srl, applying heating program based in Nardi et al., 2009 ³. Total Hg quantification by CV-ICP-MS with SnCl₂ presented 110 ± 6 and 114 ± 23 % of recovery for LOAM SOIL® and FISH MUSCLE®, respectively. Besides the accuracy and sensitivity of the system for total Hg, experiments performed showed signals for methylmercury similar to blank, allowing the application in fractionation analysis by the determination of inorganic Hg.

MEMBROS DA BANCA:
Presidente - Interno ao Programa - 2046361 - BRUNO LEMOS BATISTA
Membro Titular - Examinador(a) Interno ao Programa - 1543683 - IVANISE GAUBEUR
Membro Titular - Examinador(a) Externo à Instituição - MÔNICA HELENA MONTEIRO DO NASCIMENTO - UFABC
Membro Suplente - Examinador(a) Externo ao Programa - 1933328 - HELOISA FRANCA MALTEZ
Membro Suplente - Examinador(a) Externo à Instituição - RODRIGO MENDES PEREIRA - UFABC