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Essentials
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RapidHPLCPurityAssessment
of Radiotracers
for PETScanning.
HPLC as a tool far purity
assessment,
High Performance Liquid
Chromatography (HPLC)has long
been regarded as an accurate, precise and adaptable analytical technique offering high speed separations
with high sensitivitydetection. HPLC
has recently found a place in the
Positron EmissionTomography (PET)
laboratory for analysis of the radiotracers produced on site for in-viva studies
(see back page),
HPLCrapidly verifies
radiotracer purity,
Assessmentof radiotracer purity requires an easy, rapid analytical
method. In the case of 2-FDG, the
major radiochemical contaminants are
fluorine-18 labelled 2-fluoro-2-deoxy
acetate derivatives. The assay of 2FDG radiochemical purity can be
performed on a pBondapak NH 2
Column using o simple, single solvent
elution method Solutesare detected
with a flow-through sodium iodide
radioactivity monitor. Figure 1 shows a
sample of 2-FDG that is suitable for
use in imaging. In Figure 2, the analysis of a sample that has 20% radiochemical contamination shows that it is
unsuitable for use in in-viva imaging.
Figure 1: Quantitative analysis of
Figure 2: 2-FDG sample with unacceptable
radiotracer
purity,
contamination.
TM
The need far radiotracer purity.
The radiotracer 2-FDG is synthesized
from the commercially available substrate 1,3,4,6-tetra-O-acetyl-2-Otrifluoromethanesulfonyl-beta-D-manno
pyrannose. Side reactions that occur
during the synthesislead to products
that may not be metabolized the same
way as 2-FDG and may interfere with
the imaging process. Because this
preparation is for in-viva use, it must be
demonstrated to be sterile, ..pyrogen
free, isotonic and radionucl$idicalty,
radiochemically and chemically pure.
The FDA normally requires no more
than 10%chemical or radiochemical
contamination, but in practice, no
more than 5% contamination is considered acceptable.
,t
I 0 Minutes
10 Minul_s
Sample: Synthes,z.,_ 2FDG
Column: pi_nc3ook " N_t Calumn
Mebile Phase: C_ CN _4.© gO !0
Sample: S_mhes,zed 2:'DG
Column: uB<:naaDa_ " _
C=!_mn
Mobile Phase: CI_CN t- C oO '0
Flow Rate: ! 0 ml/m,r
Flow Rate: : 0 ml ",r,n
I_tKtot
Data-tar: _3d.ochem c:i
Rad,ccnem,col
A fast easy analysis of a 2.FDG sample _s
accomphshed on a iJBondapak NH. Column
C"r_maro_:OmS ,_3ur:esvo: Dr Me4. C-ooarno_
Waters.
The
absolute essential
for bioresearch.
The lave! of rad_ochem,ca! canram,nat_on was
found to be 20% m thJssample mak;ng ;:
inappropriate for use as a rad_orracer
dn._ers.r_ _1 _'en_.,s,
ssee ,ved:c_i Can,e,
MilliporeWaters
ChromatographYcorporation
Division
34 Maple St.
Milford, MA 01757
(508) 478-2000
ters
D,v,s,onof MILLIPORE
Purity assessmentrequires simple
HPLCinstTumentation.
Figure3: A typicalsystem
forpurityassessment.
figured to carry out purity assessment
consists of a pump to deliver the solvent, an iniector to introduce the
DellveryBu_r
or,
dCor,
t,ol
,
//---_Colledion
' ,,Wo_
Column
sample
be analyzed,
a columnand
on a
which totoperform
the separation
l
detector to "see" the compounds as
lhey elute from the column. Starting
J
_,o D_c,,
I
with a simple isocratic HPLC system,
HPLC systemscan be simple single solvent or of the mare flexible gradient elution ,'ype By simply
chang,nag the column and/or detector the same system can be used to dererm,ne rcd,ochem,cai or
solvenl gradient formation, alternative
detection methods, or advanced data
ahem,col pur,,_ of other tracers.
management to extend this technology
to olher radiotracers.
The Emergenceof PETScanning.
Positron emission tomography imaging
has been found to be a useful clinical
the primary energy source of the
brain and also an important metabolic substrate for olher tissue such as
Recommended system,
A variety of HPLC configurations are
appropriate for this analysis. Your
Walers representative can help you
determine which system is best suited
to your assay needs,
and research tool for providing informarion concerning biochemical processes in diseased tissue in-vivo.
These include localization of tumors of
the brain, breast, stomach and legs;
the study of disorders such as stroke,
epilepsy, schizophrenia, manic depression, Huntington's chorea and
Alzheimers disease; lhe determination
of AZT effects in the brain; the diagnosis of coronary artery disease and
evaluation of myocardial viability.
The utilization of PETfor both clini-
the heart under hypoxic conditions
and tumors during proliferation. 2FDG is transported across cell membranes by the protein carrier responsible for glucose transport. Once in
the cell, 2-FDG is phosphorylated by
hexokinase to 2-FDG-6-PO,,. Once
phosphorylation occurs, the molecule
stays in the cell and undergoes no
further metabolism. This allows the
tissue to be imaged by PET.
one can add capabilities for multi-
cal diagnosis and therapeutic monitoring is due in large part to the development of the radiotracer glucose analogue fluorine-18 labeled 2-ftuoro-2deoxy-D-.glucose(2-FDG). Glucose is
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