measurements
of the microemulsion blank, divided by the slope of the calibration
curve. The precision was evaluated as the relative
standard deviation (RSD). In Table 3, the RSD range obtained for
all samples are shown.
The proposed method has been applied to the determination of
Cu, Fe Ni and Zn in vegetable oils samples obtained from local vendors.
Initially, the method was verified through spike recovery
tests, by adding 2.0 and 4.0 mg kg1 of each metal (metallo-organic
standard) to three different samples. The results were obtained as
the average of three replicates of each fuel sample and are shown
in Table 4. As can be seen, the method has good accuracy and the
recoveries were between 89% and 102%. The proposed method was
then applied to Cu, Fe, Ni and Zn determination in three more vegetable
oils samples. The results, obtained as the average of three