ABSTRACT
Analysis of solution samples is often desirable because dissolution destroys the chemical and physical history of the material, which may be a source of matrix interference effects. Moreover, standards are readily prepared, and preconcentration of analytical species is possible. Several techniques have been developed for the excitation of solution samples, some of which may be used for solutions which are 10% dissolved solids. In the porous cup method, the solution is placed in the electrode and a spark discharge initiated to the bottom of the electrode. The electrode floor becomes porous, and the solution seeps through into the excitation column. A circular graphite disk, the bottom half of which is immersed in the analytical solution, may be rotated on a horizontal shaft to carry a film of solution into the spark column struck between a counter electrode and the rotating disk electrode. Other procedures such as the vacuum cup electrode may be used. Atomic emission and absorption measurements are usually made by nebulizing the solution into a flame. The same is true of the plasma jet system, where the excitation medium is a gas stabilized DC arc capable of reaching unusually high excitation temperatures. The limits given in Table 4 are in μg/ml.443 Detection Limits for Liquid Samples
Element
Porous Cup
Rotating Disk
Flame Emission
Atomic Absorption
Plasma Jet
Ag
0.02
0.1
0.3
0.02
–
Al
0.3
0.3
0.2
0.5
0.1
As
3.0
–
290.0
1.0
–
Au
20.0
–
15.0
0.1
–
B
0.1
–
250.0
–
0.05
Ba
0.1
0.05
0.03
0.9
–
Be
0.003
–
7.6
0.05
–
Bi
1.0
2.5
410.0
0.2
–
Ca
0.01
–
0.005
0.01
0.5
Cd
0.2
0.3
33.0
0.01
–
Ce
3.0
–
10.0
>10,000.0
–
Co
0.5
–
1.3
0.15
–
Cr
0.1
0.5
0.1
0.01
0.1
Cs
15.0
–
8.4
0.05
–
Cu
0.05
–
0.005
0.005
0.14
Dy
2.0
–
0.1
0.5
–
Er
2.0
–
0.3
1.0
–
Eu
0.5
–
0.0025
0.4
–
F
–
–
–
–
–
Fe
0.2
0.3
0.14
0.05
0.14
Ga
0.5
–
0.07
1.0
–
Gd
0.5
–
2.0
–
–
Ge
0.5
–
4.5
3.0
–
Hf
4.0
–
75.0
–
–
Hg
10.0
–
100.0
0.5
–
Ho
0.5
–
0.1
2.5
–
In
3.0
–
0.03
0.1
–
Ir
10.0
–
110.0
–
–
K
200.0
–
0.003
0.005
–
La
0.3
–
1.0
–
–
Li
0.1
–
0.000003
0.004
–
Lu
0.5
–
0.2
53.0
–
Mg
0.003
0.005
0.2
0.003
0.01
Mn
0.02
0.1
0.03
0.01
0.03
Mo
0.3
–
0.03
0.2
–
Na
35.0
–
0.0001
0.005
0.46
Nb
2.0
–
1.0
26.0
–
Nd
5.0
–
1.0
38.0
–
Ni
0.8
0.5
0.6
–
1.0
Os
15.0
–
10.0
–
–
P
5.0
–
–
–
1.1
Pb
4.0
5.0
3.3
0.15
–
Pd
2.0
–
1.1
1
–
Pr
2.0
–
2.0
64.0
–
Pt
1.0
–
190.0
0.5
–
Rb
–
–
0.1
0.2
–
Re
5.0
–
1.0
5.0
–
Rh
0.7
–
0.3
0.3
–
Ru
2.0
–
0.3
–
–
S
–
–
–
–
–
Sb
2.0
2.5
92.0
0.2
–
Sc
0.05
–
0.07
1.1
–
Se
70.0
–
–
–
–
Si
1.0
–
74.0
12.0
–
Sm
3.0
–
0.6
14.0
–
Sn
2.0
–
3.5
2.0
10.0
Sr
0.06
–
0.004
0.02
–
Ta
2.0
–
20.0
–
–
Tb
3.0
–
1.0
26.0
–
Te
10.0
–
1,400.0
0.5
–
Th
10.0
–
150.0
–
–
Ti
0.1
–
0.5
2.0
–
n
3.0
–
0.09
0.2
–
Tm
3.0
–
0.3
0.1
–
U
100.0
–
10.0
–
–
V
0.2
0.25
0.3
0.6
0.2
W
3.0
–
4.0
5.0
–
Y
0.1
–
0.3
13.0
–
Yb
0.04
–
0.05
0.2
–
Zn
4.0
5.0
1,500.0
0.005
0.3
Zr
0.2
0.25
50.0
–
–
From DeKalb, E. L., Kniseiey, R. N., and Fassel, V. A., Ann. N.Y. Acad. Sci., 137, 235, 1966. With permission.