ions occur at the same m/zratio as the analyte ion. For example,^32 S^16 O+and(^31) P (^16) O (^1) H+both interfere with (^48) Ti,and (^40) Ar (^16) O+interferes with (^56) Fe+.
● Matrix effectsmay occur due to excess salts or involatile solids.
Some of these interferences may be removed by the use of reaction cell tech-
nology where a gas such as helium is added so that, by ion-molecule reactions,
interfering ions may be converted into noninterfering species or removed by a
multipole filter device.
The sensitivity is generally very high for a large number of elements,
typically ten times more sensitive than ICP-AES. Since ICP-MS can scan over a
wide mass range, every element is detected simultaneously. Additionally, the
isotopes are separated so that changes in isotope ratios produced from radio-
active or other sources, or required for geological dating, may be measured
accurately. If interferences occur, an alternative isotope may be available for
quantitative analysis.
Applications With ICP-AES there is little interference from ionization, since there is an excess
of electrons present. The high temperature ensures that there is less interference
from molecular species or from the matrix. Since a large number of elemental
emission lines are excited, line overlap, though rare, may occur. Figure 3shows
the simultaneous emission of a number of elemental lines from a sample. Up to
70 elements, both metals and nonmetals can be determined.
Table 1gives details of the comparative detection limits of the various atomic
spectrometric techniques. The ICP-AES technique provides a wide linear range
of detection. For example, for lead, the linear range extends from below
0.01 ppm to 10 ppm.
Mercury in waste water may be determined by ICP-MS, using the most
abundant mercury isotope,^202 Hg. Since lead from different sources may have
different isotopic compositions, ICP-MS can be used to identify sources of envi-
ronmental contamination. Tracer studies and measurements of isotopes after
chromatographic separation of species have also proved the value of ICP-MS.
212 Section E – Spectrometric techniques
Intensity
Wavelenght
Cd 226,502
Ni 227,021
Ni 226,446
Ta 226,230
Ai
226,
346
Al
226,
910
Sn
226,991
Fig. 3. Simultaneous determination of 7 elements by ICP-AES.