Chemistry Reference
In-Depth Information
advantage in tandem column separations that capture and wash Pu on Sr-Resin and
elute it to TEVA-Resin for focusing and further purification in the determination of
Pu isotopes in seawater and sediments.
56,57
)
In the analysis of sets of aged nuclear-waste samples, Grate et al. demonstrated
two approaches.
47
In one approach, eight Sr-Resin columns were set up in parallel
with column switching provided by a multiposition valve. Each of the eight samples
was analyzed in series, switching to a new column for each sample. The analysis of
one sample using on-line detection required 22 minutes, and the set of eight could be
completed in 3 hours. Using on-line detection right after separation, there is no need
to correct for
90
Y ingrowth. In the second approach, samples were separated, and elu-
ents were collected using a fraction collector. Without on-line detection, a set of eight
samples could be processed in 1 hour and then set aside for off-line quantification.
This approach may suit the work-flow in some process laboratories, but it does require
recording the time from separation to counting for
90
Y ingrowth corrections.
Sr-Resin separations can also be set up in a renewable separation-column
approach
83
as described above for
99
Tc determinations, and illustrated in Figure 9.6.
In this case, the sample was separated and eluted from the column. The advantage
of the renewable column approach was that fresh column material could be provided
for each separation. The carryover on Sr-Resin columns, described above, is largely
due to the resin material. It was shown that automatically replacing the resin material
largely eliminated carryover from one sample to the next.
Fajardo et al. have described a “multisyringe FI” approach for automating Sr-Resin
column separations.
121
These authors used off-line counting and ICP-AES to deter-
mine radioactive and stable Sr. The multisyringe approach,
39,122
as set up for Sr-Resin
separations, is shown in Figure 9.10. This system uses flow reversals and a holding
coil associated with each syringe, so in this respect it can be regarded as a modified
SI system. Instead of a multiposition valve, a series of 3-port solenoid valves were
used to select solutions to pull into the system, and direct them for pushing out to the
column. These authors analyzed for Sr in water, soil, and milk samples. The primary
potential interference of concern in these studies was Pb, which is strongly retained
on Sr-Resin. Pb is retained even in 0.05 M HNO
3
when Sr is eluted; it does not appear
in the Sr fractions as an interference; however, it could consume binding sites on the
resin in subsequent reuse of the column. A 0.5 M H
2
SO
4
cleaning step was inserted
into the procedure between analyses to remove Pb.
Another multisyringe FI separation system design has been used in the analysis
of stable and radioactive Y, using an extraction-chromatographic material contain-
ing HDEHP adsorbed on a C
18
support.
123
Separated samples were analyzed off-line
by ICP-AES and proportional counting. This system used four syringe pumps in
parallel.
HDEHP has also been used in the development of extractive scintillating materi-
als for
90
Sr and
90
Y sensing.
95
The polymeric bead material contains both an impreg-
nated extractant and organic fluor molecules. Both
90
Sr and
90
Y are retained from
0.001 M HCl solution using HDEHP. The sensor-column scintillation signal results
from the sum of the radioactive species. Elution with 2 M HCl removes
90
Sr, leav-
ing
90
Y on the sensor column for determination. This provides two measurements to
determine two unknowns. The
90
Y can be removed from the sensor with 4 M HCl.
