ABSTRACT
Spark excitation refers to those excitation conditions in which the energy across the electrode gap varies regularly and rapidly, and typically, with a change in electrode polarity whenever the energy flow drops to zero. Spark excitation is reputed to be a precise technique with decreased sensitivity at least in relative terms. The sample electrodes, however, remain cooler and much less sample is consumed. Thus, heterogeneous distribution of the analytical species within the sample matrix may degrade the precision of the technique unless rotating sample techniques are used. The types of spark excitation for which detection limits are given in Table 3 have been somewhat arbitrarily grouped into three classifications. The AC arc here refers to a system using an open circuit potential of a few hundred volts which must be ignited by a high voltage spark on each half-cycle. The high voltage spark data are for those systems where the open circuit potentials are 10,000 to 20,000 V and are self-sustaining. The data for mixed discharges refer to some combination of spark and arc excitation. Generally, the data presented in this table are the reported determination limits. All limits are given in parts per million (μg/g).441 Relative Detection Limits for Spark Excitation of Solids
Element
AC Arc
HV AC Spark
Mixed Discharge
Element
AC Arc
HV AC Spark
Mixed Discharge
Ag
0.3
0.3
1.0
Na
50.0 *
0.4 a
0.3 a
Al
0.5
10.0
10.0
Nb
–
–
–
As
30.0
10.0
10.0
Nd
60.0
100.0
–
Au
30.0
10.0
–
Ni
1.5
2.0
1.0 a
B
0.4
2.0 a
0.2
Os
–
–
–
Ba
3.0
2.0
10.0
P
10.0
–
40.0
Be
3.0
1.0 a
1 a
Pb
2.0
10.0 a
1.0
Bi
1.0
1.0
2 a
Pd
–
–
–
Ca
0.5
0.4 a
0.4 a
Pr
100.0
50.0
–
Cd
1.0
1.0
0.2
Pt
–
–
–
Rb
–
–
–
Ce
100.0
30.0
40.0
Re
–
–
–
Co
0.4
10.0 a
1.0 a
Rh
–
20.0
–
Cr
1.0
5.03
2.0 a
Ru
–
–
–
Cs
–
–
–
S
10.0
–
–
Cu
0.1
1
0.5 a
Sb
30.0
10.0
10.0
Dy
100.0
–
–
Er
100.0
–
–
Sc
–
–
–
Eu
100.0
–
–
Se
–
–
–
F
–
–
–
Si
1.0
5.0 a
0.8 a
Fe
1.0
2.0
3.0 a
Sm
50.0
–
–
Sn
6.0
10.0 a
1.0
Ga
–
10.0 a
2.0 a
Sr
4.0
–
–
Gd
100.0
–
–
Ta
–
–
–
Ge
–
–
1.0
Tb
100.0
–
–
Hf
–
–
70.0
Te
–
–
40.0
Hg
3.0
50.0
–
Th
–
50.0
–
Ho
100.0
–
–
In
10.0
–
–
Ti
6.0
3.0 a
5.0 a
lr
–
–
–
TI
10.0
10.0
1.0
K
–
–
–
Tm
10.0
–
–
La
10.0
100.0
–
U
–
–
–
V
2.0
10.0 a
10.0 a
Li
–
–
–
W
–
–
50.0
Lu
100.0
–
–
Y
8.0
–
–
Mg
0.4
0.6 a
0.5 a
Yb
10.0
–
–
Mn
0.1
2.0 a
0.5 a
Zn
20.0
10.0 a
5.0 a
Mo
3.0
1,000.0
10.0
Zr
50.0
6.0 a
10.0 a
Detection limit.
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.