Results
Various ashing temperatures were tried. We found
that the temperature should be about 350 #{176fo}rC best
sensitivity and smallest background absorption (Figure
1). At temperatures >400 #{176th}eC sensitivity is decreased
because of irregular loss of cadmium.
The influence of different atomization temperatures
Nonspecific absorbance varied with atomization
temperature and was also different for different urine
samples, probably because of variations in salt concentration.
Therefore it was necessary to use the automatic
background corrector. To decrease the background
absorption, we diluted the urines with 0.3 mol/
liter HNO3, which on the average decreased the background
by about 80%. The beneficial effect of dilution
can be seen if one compares the background curves in
Figure 2 A and B. Even with diluted urines the back-
1When the concentration of Cd exceeds 50 nmol/liter, samples may
be diluted fivefold.
0.3
A
0.3
A
ground absorbance varied (cf. Figure 3) but always well
below the correcting capability (about 0.7 absorbance
units). We also found that the slopes of the standard
curves differed for different urine samples, probably
owing to the different salt contents of the urine samples.
Variation (CV) in slope (m), by the equation y = mx +
b, where y is absorbance and x is concentration, for 22
standard curves was 8% for evaluation by peak area, 16%
by peak height.
Statistical analysis thus showed that evaluation of
cadmium concentration by area gave less variation than
by peak height. Determination of cadmium concen