ABSTRACT
The results presented in Table 5 refer to analysis of unusually small amounts of material. A residue obtained from a preconcentration or enrichment procedure may, for example, be deposited on the spectrographic electrode for analysis. Often, unique spectral techniques may be employed to maximize the total amount of radiation collected by the spectrometer. The methods listed below are those which have gained reasonably broad acceptance. The cathode layer method previously described utilizes a DC arc as does the reduced atmosphere excitation system. The latter takes place in an enclosed chamberargon atmosphere system at intermediate pressure. A spectroscopic buffer is used in conjunction with cathode excitation. The copper or graphite spark data were accumulated with a high voltage spark discharge with the sample residue deposited on either copper or graphite electrode surfaces. The hollow cathode results were obtained by placement of the sample in a cathode of high purity from which it was vaporized and excited by a glow discharge in an inert atmosphere at low pressure. The discharge may be produced by a several hundred volt potential drop between the anode and the cathode. Detection Limits for Micro of Residue Samples
Element
Cathode Layer
Copper or Graphite Spark
Hollow Cathode
Reduced Argon Atmosphere
Ag
0.5
0.5
0.03
–
Al
0.5
2.5
10.0
1.5
As
50.0
100.0
–
–
Au
50.0
20.0
–
–
B
5.0
0.25
1.0
–
Ba
20.0
10.0
–
–
Be
0.5
0.2
0.03
0.12
Bi
50.0
5.0
–
–
Ca
0.5
10.0
–
–
Cd
200.0
20.0
30.0
20.0
Ce
3,000.0
30.0
–
–
Co
5.0
5.0
0.3
4.0
Cr
5.0
1.0
1.0
2.0
Cs
50.0
50.0
–
–
Cu
2.0
0.5
0.03
0.4
Dy
300.0
20.0
–
–
Er
80.0
10.0
–
–
Eu
200.0
2.0
–
–
F
–
10.0
–
–
Fe
2.0
2.5
3.0
3.0
Ga
5.0
100.0
0.03
10.0
Gd
300.0
10.0
–
–
Ge
10.0
–
–
–
Hf
50.0
50.0
–
–
Hg
100.0
10.0
–
–
Ho
90.0
20.0
–
–
In
10.0
10.0
–
–
Ir
50.0
500.0
–
–
K
5.0
10.0
10.0
20.0
La
400.0
2.0
–
–
Li
0.1
0.2
0.1
1.0
Lu
30.0
1.0
–
–
445Mg
1.0
1.0
0.03
0.2
Mn
2.0
0.25
0.03
1.3
Mo
2.0
5.0
–
1.6
Na
1.0
10.0
0.03
7.0
Nb
50.0
20.0
–
–
Nd
2,000.0
20.0
–
–
Ni
10.0
1.0
1.0
3.0
Os
10.0
–
–
–
P
500.0
10.0
30.0
30.0
Pb
10.0
5.0
10.0
1.0
Pd
5.0
50.0
–
–
Pr
900.0
20.0
–
–
Pt
5.0
2.0
–
–
Rb
20.0
20.0
–
–
Re
500.0
200.0
–
–
Rh
30.0
–
–
–
Ru
10.0
–
–
–
S
–
–
–
–
Sb
20.0
10.0
100.0
2.0
Sc
10.0
0.5
–
–
Se
–
–
–
–
Si
5.0
10.0
1.0
3.0
Sm
2,000.0
20.0
–
–
Sn
5.0
–
10.0
7.0
Sr
5.0
50.0
–
–
Ta
400.0
10.0
–
–
Tb
300.0
100.0
–
–
Te
50.0
50.0
–
–
Th
2,000.0
20.0
–
–
Ti
5.0
2.5
–
2.0
Tl
20.0
50.0
–
–
Tm
30.0
5.0
–
–
U
400.0
100.0
–
–
V
5.0
1.0
–
–
W
500.0
10.0
–
–
Y
8.0
0.5
–
–
Yb
3.0
1.0
–
–
Zn
100.0
10.0
3.0
45.0
Zr
20.0
2.5
–
–
From DeKalb, E. L., Kniseley, R. N., and Fassel, V. A., Ann. N.Y. Acad. Sci., 137, 235, 1966. With permission.