The instrumental factors involved in the determination of the
cadmium concentration in vinegar by ET AAS were optimized in
two steps. First, a two-level full factorial design was performed
with the following variables: aluminium modifier mass, pyrolysis
time, pyrolysis temperature and atomization temperature. In the
step second, a Box–Behnken design was also used to determine
the critical conditions for these factors.
The two-level full factorial design (24) was established, with
four additional experiments at the central point. The experimental
variables as coded and real values for the four factors and several
chemometric responses are shown in Table 2.
The effects of the factors and their p values when employing the
absorbance as the chemometric response were calculated and the
results are shown in Table 3.
These data demonstrate that all these factors have statistically
significant effects on the analytical signal under the experimental
conditions established. The atomization temperature had a positive
effect, which was the largest among the four factors. The
positive effect indicates that an increase in the atomization
temperature contributes to an increase in the absorbance. This
relationship can be observed by comparing the absorbances
obtained at temperatures of 1300 and 1800 C. The other
factors were significant; however, the magnitudes of these effects
were considerably smaller than that of the effect of the atomization
temperature.
An evaluation of the factorial design was also performed using
only the QEI as the chemometric response. The effects for the four
factors and their p values are also summarized in Table 3.
The effect values obtained demonstrate that all four factors
were statistically significant. The atomization temperature had a
positive effect, and it had the greatest influence on the peak
shape. The data presented in Table 2 show that the highest QEIs
were obtained at an atomization temperature of 1800 C. The
modifier mass was the second most important factor that affects
the value of the QEI. This factor had a negative effect, and thus,