Banca de DEFESA: PATRICIA CRISTINA COSTA LADEIRA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : PATRICIA CRISTINA COSTA LADEIRA
DATA : 25/04/2022
HORA: 08:00
LOCAL: Santo André (virtual)
TÍTULO:

Development of different methods of determination of mercury by the application of generation cold steam and UHPLC couplings to the ICP-MS

PÁGINAS: 77
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Analítica
ESPECIALIDADE: Análise de Traços e Química Ambiental
RESUMO:

Mercury is an element off natural occurrence, being present in the different spheres of the Earth. The high toxicity of its compound makes human exposure to them, through different routes, a worldwide concern, encouraging the development of analytical methods applied to different environmental and biological matrices for determinations of total Hg, fractionation, and chemical speciation. Thus, in this work, different analysis methods were developed applying cold vapor generation (CVG) and ultra high performance liquid chromatography (UHPLC) hyphenated to mass spectrometry inductively coupled plasma (ICP-MS). Initially, a method to reduce the memory effect in the ICP-MS was evaluated aiming at the determination of total Hg with greater precision. It was verified that the addition of 2-mercaptoethanol (2-ME), at the concentration of 0.05% v/v, to the work solutions solved the problem of memory effect enabling analysis without several cleaning steps between measures. For this method, were obtained limits of detection (LOD) and quantification (LOQ) equals to 5.25 and 17.5 ng g -1 , respectively, and 98% of recovery for the certified reference material (CRM) TORT-3 (NRCC). A cold vapor generation method coupled to ICP-MS (CVGICP-MS) was optimized aiming the application in total Hg and fractionation determinations. For this, a flow injection system was assembled for introduction of sample and reducing agent, and different experimental conditions, as argon flow rate and reagents concentrations, and instrumental parameters of ICP-MS, as number of sweeps, peak pattern and integration time, were optimized. The study was realized for two reducing agents, sodium borohydride (NaBH4) and tin(II) chloride (SnCl2), and the second presented higher sensitivity for total hg determination, with LOD and LOQ of 2.25 and 7.50 ng g-1 , respectively. The method accuracy was evaluated analyzing different CRM after acid digestion in microwave, obtaining 114% of recovery for FISH MUSCLE (ERM® - BB422) and 110% for LOAM SOIL (ERM® - CC141). The application of this reducing agent also provided selectivity for inorganic Hg, allowing the application in fractionating analyses. Since the chelating compounds application for memory effect reduction can difficult the analyte reduction losing sensibility, the problem was minimized evaluating varied solutions and washing procedures between measures. The best result was obtained applying acid solution containing gold. Finally, the chemical speciation was realized transferring a traditional method of HPLC-ICPMS to UHPLC-ICP-MS, by column substitution and reducing the sample volume injected. Applying the UHPLC, was obtained the Hg2+ and methylmercury (MeHg+ ) separation in 1 min reducing the consumption of mobile phase and argon. The analysis of TORT-3 and samples of muscle and liver fish showed the separation efficiency in real samples and the method accuracy getting recoveries between 98 and 105% of total Hg adding the species concentration, showing the applicability of the method for tissues and other samples.

MEMBROS DA BANCA:
Presidente - Interno ao Programa - 2046361 - BRUNO LEMOS BATISTA
Membro Titular - Examinador(a) Interno ao Programa - 3047441 - MONICA BENICIA MAMIAN LOPEZ
Membro Titular - Examinador(a) Externo à Instituição - JULIANA MARIA DE OLIVEIRA SOUZA - UFJF
Membro Titular - Examinador(a) Externo à Instituição - MACIEL SANTOS LUZ - IPT-SP
Membro Titular - Examinador(a) Externo à Instituição - AIRTON DA CUNHA MARTINS JUNIOR
Membro Suplente - Examinador(a) Externo à Instituição - MARIA FERNANDA HORNOS CARNEIRO - PUC
Membro Suplente - Examinador(a) Externo à Instituição - BRUNO ALVES ROCHA - UNIFESP
Membro Suplente - Examinador(a) Externo à Instituição - RODRIGO PAPAI DE SOUZA - IPT-SP