Environmental Engineering Reference
In-Depth Information
Table 9.1 Ionization energy for selected elements and
fraction of the ionized species in the argon plasma
Ionization
Degree of
Element
energy (eV)
ionization (%)
Alkali metals
Li
5.39
99.99
Na
5.14
99.9
K
4.34
99.9
Metals
Cu
7.73
90
Zn
9.39
75
Pb
7.42
97
Cd
8.99
65
Ni
7.64
91
Hg
10.44
38
Metalloid
As
9.79
52
Se
9.75
33
Nonmetals
P
10.49
33
S
10.36
14
Cl
12.97
0.9
as P, S, and C to have emission lines. This explains why ICP-OES is not commonly
used for nonmetal analysis.
ICP can theoretically analyze almost all elements. This is in significant contrast
to only approximately 70 elements (metals and nonmetals) that can be analyzed by
atomic absorption and flame emission spectroscopy. Another significant advantage
of ICP is its ability to analyze multiple elements simultaneously as compared with
the absorption-based atomic spectroscopy, which can analyze only one element at a
time. This ability is the result of the simultaneous emission of multielements and the
ability of modern optical devices to resolve various wavelengths from complex
emission spectra.
We interchangeably used ICP or ICP-OES for the above discussion. Note that
various names have been used for the plasma emission spectroscopy, including ICP,
ICP-AES, and ICP-OES. The use of ICP should be avoided because this represents
only the method of energy transfer. ICP-AES is more commonly used, likely
because users and manufacturers who in many cases have worked with atomic
emission spectrometry. However, the use of the term ''atomic'' is probably
misleading because in ICP, most particles in the plasma are ions rather than atoms—
unlike what we discussed in other atomic absorption and emission techniques. With
this regard, ICP-OES (inductively coupled plasma-optical emission spectrometry)
is technically a more proper term.
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