In addition, the cadmium content in all samples was well above the limit of quantification, so that a further increase in sensitivity
was not necessary. The positive intercept of the correlation curve
of about Aint = 0.01 s with the integrated absorbance axis is due to
the blank signal caused by the modifier mixture.
Pyrolysis curves have been established for a wheat flour sample
and an aqueous solution using 10g Pd+3gMg + 0.05% Triton X-
100+0.1% H2O2 as chemical modifier in both cases, and are shown
in Fig. 3. The atomization temperature of 1600 ◦C has been optimized
in previous work [37]; it is also in agreement with literature
data for a transversely heated atomizer [38] and was not further
investigated. The integrated absorbance values for the wheat flour
sample in Fig. 3 have been ‘normalized’ for 2mg of sample because
of the above-discussed difficulties to weigh and introduce repeatedly
the same sample mass into the graphite furnace. Hence, a
sample mass close to 2mg has been weighed accurately, and the
integrated absorbance obtained for the actually introduced sample
mass has been multiplied with the factor corresponding to
the deviation of the actual sample mass from 2.00mg. It is obvious
that cadmium in aqueous solution is thermally stable up to
900 ◦C under the selected conditions, and no losses of cadmium
are observed from wheat flour at least up to 800 ◦C. A pyrolysis
temperature of 800 ◦C has therefore been chosen for all further
investigations.