Navegando por Assunto "Rio Tucunduba - PA"

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Aplicação da cromatografia líquida de alta eficiência na investigação de hidrocarbonetos policíclicos aromáticos em testemunhos sedimentares
(Universidade Federal do Pará, 2013-07-31) EVANGELISTA, Camila do Carmo Pereira; KAWAKAMI, Silvia Keiko; http://lattes.cnpq.br/5306256489815710
Polycyclic aromatic hydrocarbons are organic (PAH) compounds originated from natural or anthropogenic sources and are considered priority substances by environmental agencies because of carcinogenic and mutagenic potentials. Therefore, rapid and low cost analytical methods for these compounds are of significant relevance for environmental purposes. The present study aimed the optimization of an analytical method for PAHs using High Performance Liquid chromatography with a diode array detector (HPLC-DAD) for the application to an estuarine sediment core. For the optimization and evaluation of the method, a sedimentary column measuring 46 cm length was collected at the mouth of the Igarapé Tucunduba (Belém, Pará) and sectioned in 2 cm portions. After dryness, 30 g of each portion were extracted with a mixture of dichloromethane in acetone in ultrasound bath for 40 min. the extracts obtained were centrifuged, purified on silica gel as a clean-up adaptation mainly to retained fine particles, then concentrated using vacuum evaporator and filtered through 0,2 μm nylon membrane before HPLC injection. Samples spiked with 16 PAH analytical standards and procedural blanks were processed on the same way. The parameters assessed showed: (1) good linearity, the calibration curves presented high correlation coefficients ; (2) adequate accuracy: relative standard deviations within acceptable values with 2,1% for acenaphthylene and maximum of 19,7% for fluoranthene; (3) low detection limits between 0,004 to 1,085 ng g-1 which make in situ determinations feasible; (4) adequate recovery for traces with minimum of 40,0% for acenaphthylene and maximum of 103,1% for benzo(k)fluoranthene. The total PAH concentration in the sediment core ranged between 60,77 to 783,3 ng g-1 dry sediment. The optimized method showed advantages over the traditional methods based on soxhlet extrations and clean up adsorption columns in terms of time of analysis and reduced costs with the use of smaller amounts of solvents. The limitation, however, was de coelution of some compounds, which is probably due to the low efficiency of the chromatographic column that was available at the time of the analysis. The method was applicable to estuarine complex samples, rich in silt and clay. Diagnostic ratios using parental PAHs indicated petrogenic sources at 24 - 26 cm and 28 – 30 cm depth; and pirolitics sources at 6 - 8 cm, 10 - 12 cm , and 14 - 16 cm respectively.