ABSTRACT
While the absolute detection limits given in the previous table are indicative of what can be achieved in the general case, consideration of relative detection limits reported serves as useful supplementary information. The limits given in Table 2 are expressed in parts per million (μg/g) as determined by variations of DC arc excitation techniques. The open arc column lists data accumulated by operation of the arc in air under conditions deemed optimal for the sample type in question. The carrier distillation data refer to the technique of blending a sample with a carrier material and subsequent vaporization and excitation of the blend. Thus, selective volatilization may be combined with the use of the spectroscopic buffer to provide some degree of control over the vaporization-excitation process, thereby enhancing the sensitivity in many instances. Controlled atmospheres may be used to reduce background, change vaporization rates, and obtain a higher energy distribution in the arc column. A general indication of changes in the detection capabilities can be obtained by cross comparison of the columns. The cathode layer data refer to use of the sample electrode as the cathode rather than the anode and observation of the light emitted from the region closely adjacent to the cathode. Enhancement is typically greatest for the elements with the lowest ionization potentials. The sustaining arc data refer to the use of an AC arc. This column provides a general comparison between AC and DC arc capabilities. It should be emphasized that the results given were obtained from the general literature and reflect differences in sample types, technique, equipment, definition of detection limit, etc. The data should consequently be used only as a general indication of the relative merits of the different excitation approaches. Reported Relative Detection Limits for Arc Excitation
Element
Open Arc
Carrier Distillation
Controlled Atmospheres
Cathode Layer
Sustaining Arc
Ag
0.1
0.05
0.001
1.0
1.0
Al
0.5
1.0
0.1
–
1.0
As
10.0
10.0
0.1
3.0
–
Au
5.0
0.3
0.5
–
–
B
0.2
0.08
0.4
–
–
Ba
1.0
1.0
2.0
5.0
10.0
Be
0.1
0.1
0.005
10.0
–
Bi
0.4
0.5
0.03
0.2
–
Ca
1.0
1.0
0.01
–
2.0
Cd
0.2
0.3
0.08
–
–
Ce
10.0
300.0
5.0
–
–
Co
3.0
0.5
0.04
2.0
–
Cr
0.5
1.0
0.5
1.0
1.0
Cs
2.0
30.0
500.0 *
–
–
Cu
0.1
0.3
0.1
–
–
Dy
5.0
–
2.0
–
0.8
Er
S.O
–
2.0
–
–
Eu
5.0
1.2
2.0
–
–
F
100.0
–
–
–
–
Fe
0.05
1.0
0.4
–
2
Ga
3.0
10.0
0.1
1.0
–
Cd
10.0
–
2.0
–
0.5
Ge
1.0
0.2
0.1
–
–
Hf
1.0
–
10.0
–
200.0
Hg
0.5
–
0.3
–
–
439Ho
5.0
–
2.0
–
30.0
In
1.0
0.5
0.1
–
–
Ir
50.0
5.0
4.0
–
–
K
1.0
5.0
1,000.0 *
–
3.0
La
0.5
100.0
2.0
30.0
–
Li
0.5
0.5
500.0 *
–
1.0
Lu
5.0
–
2.0
–
0.1
Mg
0.01
0.5
0.1
–
1.0
Mn
0.05
0.5
0.03
–
1.0
Mo
3.0
1.0
10.0
1.0
–
Na
0.5
1.0
500.0 *
–
3.0
Nb
10.0
10.0
5.0
–
30.0
Nd
20.0
–
5.0
–
–
Ni
1.0
1.0
0.1
2.0
3.0
Os
50.0
–
80.0
–
–
P
20.0
8.0
0.15
–
–
Pb
0.02
1.0
0.3
10.0
–
Pd
1.0
1.0
1.0
–
–
Pr
20.0
–
5.0
–
–
Pt
5.0
–
4.0
–
–
Rb
1.0
10.0
1,000.0 *
–
–
Re
50.0
–
10.0
–
–
Rh
10.0
5.0
0.6
–
–
Ru
100.0
–
0.4
–
–
S
–
–
0.3
–
–
Sb
5.0
4.0
0.1
50.0
–
Sc
1.0
–
0.5
–
0.5
Se
20.0
–
500.0 *
–
–
Si
0.5
2.0
0.4
–
10.0
Sm
20.0
3.0
5.0
–
–
Sn
1.0
0.5
0.1
5.0
–
Sr
5.0
1.0
5.0
–
–
Ta
30.0
–
–
–
60.0
Tb
50.0
–
10.0
–
2.0
Te
10.0
–
40.0
–
–
Th
100.0
–
500.0
–
–
Ti
1.0
2.0
1.0
–
–
TI
0.05
0.3
0.3
50.0
–
Tm
5.0
–
2.0
–
0.5
U
100.0
–
500.0
–
–
V
5.0
1.0
5.0
5.0
–
W
20.0
10.0
100.0
–
–
Y
5.0
–
2.0
–
–
Yb
1.0
5.0
0.5
–
–
Zn
1.0
8.0
0.1
100.0
3.0
Zr
10.0
10.0
10.0
Most sensitive line not used.
From DeKalb, E. L., Kniseley, R. N., and Fassel, V. A., Ann. N.Y. Acad. Sci., 137, 235, 1966. With permission.