Evaluation of Mercury Concentration in Biodiesel Samples by Photochemical Vapor Generation

Abstract

In this paper, the photochemical vapor generation coupled with atomic absorption spectrometry was used to assess the concentration of Hg in biodiesel samples. The main parameters to assess the best conditions for the photochemical vapor generation of Hg were investigated (sample mass, formic acid concentration, irradiation time and gas flow rate). Volatile species of Hg were generated in biodiesel samples prepared in 20% (v/v) formic acid and 76% (v/v) ethanol. Analytical curves were generated using inorganic (Hg 2+) and organic standards (CH 3 Hg + e C 2 H 5 Hg +) in ethanol and showed correlation coefficients higher than 0.99. The limits of detection and quantification, in µg L-1 , were 0.01 and 0.05, respectively. Due to the lack of biodiesel samples with a certified concentration of Hg, the accuracy was evaluated by assessing the recoveries of species of Hg added to the samples, obtaining values ranged from 101.0 to 111.9% of recoveries. The relative standard deviation values were lower than 0.1%, indicating an excellent precision of the method. No Hg was detected in the biodiesel samples, considering the obtained limit of detection. The proposed method is sensitive and the sample pre-treatment is simple and practical.