The presence of some elements in gasoline above certain concentration
limits is undesirable, not only by the possibility of damaging
motor parts and poor performance of the fuel, but also because of the
pollution caused by the release of toxic elements to the atmosphere
due to the combustion of the fuel [1]. Anthropogenic activities are of
main importance in the mobilization of mercury and its compounds
and, among them, the burning of fossil fuels is of special concern [2].
According to the literature [3], different Hg species can be present in
petroleum and in its fractions. Metallic elements are normally present
at very low concentrations in gasoline, requiring very sensitive techniques
or pre-concentration steps for their determination [4].
However, few papers on the determination of total mercury in
petroleum products have been published. Excellent limits of detection
using cold vapor atomic absorption spectrometry (CV AAS) [2] or
cold vapor atomic fluorescence spectrometry (CV AFS) [5] have been
reported, but they can be too dangerous for common use when a
previous BrCl oxidation of the sample is employed [6]. Mercury is
a difficult element to be measured in complex matrices because the
matrix must be destroyed at elevated temperature without loss of
the analyte or contamination. Furthermore, the determination of Hg
in gasoline and petroleum products samples is difficult due to the volatile
nature of both mercury and the matrix, which may lead to severe
loss. The difficulties of getting this kind of sample into aqueous solution
are not unique to mercury determination [7]. In this way, a recent
work was published on the determination of mercury in petroleum
products by isotopic dilution cold vapor inductively coupled plasma
mass spectrometry (ID-CV-ICP MS) using wet ashing in a closed vessel
system [8]. Sample preparation as microemulsion has been applied
also successfully for the determination of mercury and other elements
in petroleum products, such as mercury in naphta by ET AAS with
direct pre-concentration in the graphite tube, using palladium as modifier
and multiple injections [9], determination of As and Sb also in
naphta by GF AAS using Ir as permanent modifier [10] and determination
of mercury in gasoline by CV AAS with reduction in the microemulsion
[2]. Sample preparation as emulsion has also been employed
for vegetable oils for the determination of Hg, As and Cd by flow