Geração Termoquímica de vapor induzida por aquecimento com radiação infravermelha para a determinação de mercúrio por CVAAS

Abstract

The oil spill in the Brazilian coast in 2019, has reached more than 980 beaches and approximately 3000 km in lenght of the Brazilian coast, causing negative impacts on the environment. Crude oil can have harmful constituents, including toxic metals how Hg. Studies on the chemical characteristics of the oil are important to elucidate issues such as composition and toxicity. The objective of this work was to develop a thermochemical vapor generation method to determine the total mercury content in sediment samples contaminated by crude oil. The development of the method started with the evaluation of the experimental conditions, including gas-liquid separator (GLS), concentration of formic acid, sample flow, reactor temperature and carrier gas flow. The greatest efficiency in the generation of volatile species was achieved with the use of 20% formic acid v v-1, sample flow of 4.5 mL min-1, reactor temperature of 140 ºC and carrier gas flow of 20 mL min-1. The calibration curve for the proposed method a correlation coefficient greater than 0.99. The accuracy was confirmed using certified reference material (PACS-2), with a recovery rate of 93.81%. The precision had a relative standard deviation of around 5%. Considering the best conditions of the variables, a detection limit of 0.44 μg kg-1 was obtained. The developed method was applied to determine the total Hg content in samples of marine sediment from the regions affected by the oil spill. The analyzed samples showed mercury concentrations in the range of 0.17 to 0.29 mg kg-1. Therefore, it was possible to develop a simple, fast, low-cost analytical method with an environmentally friendly approach when compared to other conventional vapor generation methods.