Figure 8.14
'Echellogram' showing the three dimensional
nature of a typical spectrum.
(Courtesy of Varian Ltd)and this feature offers a considerable improvement in precision over arc/spark emission methods.
Relative precisions are in the range 0.5–2%. The high temperatures of plasmas lead to a high degree of
atomic excitation and thus high sensitivity for measurements, which may often be made at levels below
0.1 ppm and with a linear response up to 1000 ppm or more. Figure 8.15 shows a typical calibration
curve. The high temperatures also ensure that virtually all compounds are broken down to their
constituent elements. Thus matrix effects are largely eliminated. Furthermore, background interferences
from molecular species, which are so often a problem in other methods of atomic spectrometry, are
removed. As the plasma is not in contact with the electrodes or jet no contamination is introduced from
this
Figure 8.15
Calibration curve for ICP determination of lead
in sea water showing the wide linear range.