140,
4-7
smoles.
.
.
Verv larse dilution factors
.
=
.
sere requir2d in order to achieve iso.
1
=
~
topic ratios typical orf most analytical samples.
A value or= 2.1: x 110 -3 for
the
+49
4i29. 127,
i;
T atom ratio was determined from the dilutions and mass spectrometric
data Cor one of these isotopically diluced iodine aixtures; this aixture is
still used in our laboratory for long-term measurement control.
mixture has also been used as a routine comparator standard.
This isotopic
A l-to~10 mg ali-
quot of the elemental iodine isotopic mixture is irradiated with samples or
other standards to be analyzed.
After irradiation the todine is further
puricied by solvent extraction and precipitated as AgI.
determined from the weignt of the aAgl.
The
2
128, 127
/
I,
The iodine content is
126_,1 2 7,
130, 1 29 t
I/
and
/
activity=to-mass ratios can then be determined from the Agl weight, the known
129_
-
z/
-
127
IL ratic and the gamma-ray spectrometric data.
.
.
.
of Agl radiometrically with
110m
,
Measurement of the amount
.
Ag tracer has also been sarisfactory.
case, excess Ag+ containing a known
110m
.
.
in this
Ag/Ag ratio is used to precipitate the
‘
ge
.
4:
.
.
110m
Lodine and the total 1lodine is determined from the
Ag content of the Agi as
measured by gamma-ray spectrometry.
.
.
precipitation.
Both methods depend upon stoichiometric Agl
1
.
.
.
.
The i Om. radiometric method, however, is not affected by mois-
ture, as are the Agl weight measurements.
.
.
127
.
.
.
.
Another standard material we have used for
I activation analysis caliDrations of our comparator standard is hexaiodobenzene (c,1,).
this method agreed with the Ag! calibration methods.
The results of
Hexaiodobdenzene is avail-
able as hizh purity (99.9%), weizhed sellets of abouc 1.55 g each.
Low neutron
exposures are required due to the large amounts of iodine in the pellets.
A mixed
125,
’
t 27 I
’
2
129
t comparator standard has also been prepared to sin-
the
ee
.
127.
plifv analysis and to reduce the amount of
I in the standard.
.
This reduces
“8; activity to measurable levels within a few hours of reactor discharge