Banca de DEFESA: DESIRÉE MARIANNE SALES SILVEIRA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : DESIRÉE MARIANNE SALES SILVEIRA
DATA : 04/03/2020
HORA: 14:00
LOCAL: auditório
TÍTULO:

New sample preparation device: development and validation of a fast, cheap and green method to analyze aqueous samples by gas chromatography

PALAVRAS-CHAVES:

IT-SPME, volatile organic compounds, pesticides, method validation, PMMA

PÁGINAS: 68
GRANDE ÁREA: Ciências Exatas e da Terra
ÁREA: Química
SUBÁREA: Química Analítica
ESPECIALIDADE: Instrumentação Analítica
RESUMO:

In chemical analyses, sample preparation is the most time consuming step of all analytical process and the main source of errors in the final result. Available methods such as Solid Phase Extraction (SPE) and Solid Phase Microextraction (SPME) are usually laborious, expensive and fragile, like SPME fibers, which are highly sensible and may break with a little mistake, stopping its use. Therefore, improvements in the process are desirable and important to achieve better analytical results. This work presents an innovative one-step and solvent-free method of aqueous sample preparation for gas chromatography, using Poly(Methyl MethAcrylate) (PMMA) as extractor phase, for the trapping of Volatile Organic Compounds (VOC) from aqueous samples. The process consists of a sample flow through the inside of a liner internally coated with PMMA. This flow is maintained until the reach of the thermodynamic equilibrium time of the analyte between the PMMA and the aqueous matrix. After the absorption of the analyte by the polymeric phase, the liner is then inserted into the gas chromatograph for desorption and chromatographic separation. The method was tested using an aqueous solution of 1-dodecanol, a mix containing 13 alkanes and a standard containing 16 pesticides. The GC-MS system was composed by an Agilent 7890A GC (Supelco HP-5MS capillary column) coupled with an Agilent 5975B Single Quadrupole MSD, under SCAN mode. The method was successfully able to identify all the analytes, and it was also optimized in order to improve signal’s resolution, reduce the baseline and decrease signals from interferes. It was evaluated how the molecular weight of PMMA affects the absorption power, comparing the polymers of 120,000 g mol-1 and 350,000 g mol-1, and it was found no significant differences, however the PMMA of higher molecular weight was more stable and resisted thermal degradation by more chromatographic analysis than the PMMA of lower molecular weight. The method was validated for the analysis of five pesticides - heptachlor, aldrin, heptachlor epoxide, endosulfan and dieldrin - obtaining LOD (Limit Of Detection) values in the range of 1,46 to 4,26 μg L−1 and LOQ (Limit Of Quantitaion) values in the range of 5,95 to 8,70 μg L−1 . The accuracy of the method was assessed by studying intra-day repeatability, obtaining RSD (Relative Standard Deviation) values in the range of 5.60% to 16.70%. The linearity of the method was investigated with the construction of the analytical curve for the five pesticides, obtaining R2 values up to 0,99018. The new method is a viable, cheap, fast, and safe alternative for extraction and pre-concentration of volatile analytes in aqueous samples for gas chromatography analysis, besides being an innovative application, that redefines a liner’s function in the equipment.

MEMBROS DA BANCA:
Presidente - PATTERSON PATRICIO DE SOUZA
Interno - ILDEFONSO BINATTI
Externa ao Programa - PATRICIA SUELI DE REZENDE