Nagoya University
NagoyaUniversity

Articleforthe Proceedingsof theInternational
Symposium on Radiometric Dating Studies,Nagoya University

Development of an Automated Combustion and Gas-fed Ion Source System
for Environmental Monitoring and Biomedical i4C Applications
W,'E.

Kieser,K. Leung,N. Krestina,
R. P.Beukens,X-L Zhao and A, E. Litherland

Environmentalmonitoringin the event

ofanaccidentalormalicious

releaseofi4C-laden

would
requirethe analysis of a largenumberof samples,at levels
between 1 and 104
times modern,
A similar levelof i4C concentration
ispresentin samples resulting from the use ofi4C
fbr tracing in bio-medicalapplications,fbr fo11owingthe pathways ofparticularly
metabolites in the development of pharmaceuticals. These applications
also generatelargematerial

numbersofsamplestime andpreparationandboth areas
labour.The recentofbenefitfrom reduced
sampleof gas-fedion sources
permitsi4C,
the graphitization
processand, fbrhigh levelsof
applicationcommercial

the developmentof systems which eliminate
increasethc analytical throughput.

would

availability

includcs
an automatedcombustion
unit to producecarbon dioxide,a gas transfer
isand storage system and the directgenerationof carbon anions fromthe C02
beingdeveloped
at IsoTrace.
This system was primarilyfundedfbr environmental
monitoring
purposesby theA system which

Canadian CBRN

Research and Technology lnitiativeprogram,but will be kept in a state ofreadinessthrough itsuse fbrbiomedicalanalysis. With the substitution of alternate transferlines,
i4C
it is expectedthat this systemwM
also
be quite usefu1 fbr the measurements
ofconcentrations
inthe range ofO to 15 ka BP. A plan view ofthe equipment
isshown infigure1.

loAccetenator

Figure 1:Planvicw ofthe injectionlin¢ ofthe
IsoTraceAMS system. The electrodes ofthe electric analyser
or the newSO-110 source can be
can be rotated so that ion beams from ejther the older GIC834 ion sourcese]ected
forinjection
intothe acceierator.

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The ion source isa High VoltageEnginceringmodei SO-110 hybridgas ! solid source, which
has been installedon the IsoTraceAMS
iajection
lineat the -450 portof the rotatable electricanalyser.
The combustion
unit is an EIementar Vario ELIII CNS
elementalanalyser
which
separatetrapping
and release fbrthe analyte gases.A gas dilution,
storage and transfer
provideslinehas being buiitlocally to connect these two units, A schematic
diagram,illustrating
theinternalfunctionsofthese units, isshown inFigure 2.

EIementatAnalyzer

TransterLine

lladoELllCAfsp
flY7ementar

lonSource
aVWEE SO-ffO-20CV

Sampte Loader

Figure2: Schematicshowing
the functionsof the three components
combustion
tube, R isthe reduction tube, D is a thermal conductivity
Water traps arenotshow,

to simplify

system.
Item C isthe
detectorand those labelled
V are vents.

of the automatedthe illustration.

The principal
tasks of the gas transferlineare to accommodate
the dischargeof C02 in the He
carrier stream from the elemental
analyserand to prepareitfbridjection
intothe ionsource, At aconstant flow rate of 200 ml per minute,
the C02 isreleased as a peak in concentration over adurationranging from 1 to 3 minutes as shown jn Figure3. The ion source requires a steadyflow ofa unifbrm conCentratlOn Of Name
Peeak co2' co3.e6,OS
14,09[mVJ [+C]
PEAK,glOZ]ene
1C02 in He at a rate of - 200 pt1per FSIe!Ncr.
1800
15S
minutc,The transfersystem includes
tvptspv#kt"nw-C02Trap
mixingaunit
which
iajects
15PO
130
additional
He into the C02 ! HeTemperature
12eo
1[:4mixture
frornthe elcmental analyzer
N2
C02
to produce a stream with relatively
see?sconstant C02 concentration.
aeet

The amountof He iniectecl
isdeterminedby a mass flow controller
which
fbllowsthe profileof the C02
by the thermal
peak measured
conductivity detector(TCD) in theulaiD

12e:

24eT,3..S.fi

6oe

S23oe

2eet]

TCDSignal?2es4e960l.4.e.B.]6De
Figure3: Displayfrom the elemental
analysercontrol
screengas stream is then fed intoa heated showing th¢ signal from the therma] conductivity
detectorandstainless steel
loop and
finallytcmperature ofthe C02 trap,The latter
adsorbs the C02 at room
iniected
intothc ion source.
A temDerature and releases itat --1400C
elemental

analyser.

The

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schematicofthe transferlineisshown in figure4, An advanced
versionof this line
will consist
loops,
so that the elemental
analysercan be processing
the ncxt sample while theisbeinganalysed on the AMS system.
oftwo sample

firstoneM)thg fee

fivm'sVbnt

he tblcbivdon

Vlont
tolanSotnve

Figure 4: Schematicofthe C02 transferand dilution
line.VaLvc V2 allows the mass fiow controller MFC1 tobe adjusted and then switched intothe mixing tee when the C02 pulse from the elemental
analyserpassesthrough the tee. When the C02 1 He mixture anives
at the end
ofthe
samplcloop,valve V3 switches the loop
to feed the source.

For the analysis of gas sarnples, thc SO- 110 uses a targetcontaining a titanium pelletever which
the C02 gas isflowed while being bombarded by the caesium
sputtering
beam, as shown inFigure5. As the Ti pelletissputtered, a small (--0.5mmdiameter)crater isfbrrnedand the C'ion current tends to increase.The C- current can be optimized by adjusting parameters such as
the feedrate of C02 intothe source, the intensityof the Cs beam and the position
ofthe Ti pel]etwithinthe target.At the highcurrents of Cs required fbrgas mode operation, the original designof the Cs feedto the ionizer
one side) produced a Cs spot on the targetapproximately
O.5(frommmoff centre (Figure6). We havejustinstalleda re-designed Cs feedsystem
inwhich the Cs
enters from six holessymmetricallyspacedaroundthe axis ofthe ionizer.
This has significantly
improved the centring of the Cs spot on solid targetsas well as the stability and jntensityof theC' current producedas shown inFigure7.
C02gaslnlet

TargetS

rim

TitaniumpelletSputtercrater
Figure 5: Cross section
environmentoftarget

piece usedto create theforproducing C- ion beams from C02 gas

Figure 6i Microphotograph oftargetshowing
offLaxis
crater.

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1.2

qeE9ts1.1oo"

a.oo
too

200

3oo

400

500

300

400

5oo

Cycle Number

2.0?e･

19e9ioO

1.8p

1.7

O

100

2oo

CycleNumber
Figure 5:
ofi2C3'the annularcurrent

measuredcaesium

vapourinthe post accelerator'feed,
withothersource

Faraday cup,
conditions

analysedrernaining

befbreandthe saine.

after the installation
Improvements in boththe stability and intensityof the current can be seen.

tn order to operate the gas transfer line
andofto synchronize with itthe operation
the elemental
analyzerandthe ionsource,asystem

logic controller
implemented, OnAMS

systemprogrammed(PLC) is being

using

afrom thethe PLC initiates

a command

computer,the combustionof the next sample,
reads
the thermal conductivity detectorsignal
and operates the mass flowcontroller on
the He dilutionfeed to providc aconstant
C02 to He ratio, inserts
a cleantarget intothe SO-110 and switches thestorage
loop valve to feed the sample
into the source,
A schematicof thissystemisgiveninFigure8.
Figure6: Schematicshowing
the componentsandcommunications
linksofthe PLC based control system.

36--

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For environmental monitoring of i4C under emergency conditions, samples such as vegetation,soil, air filters
or surfaee swipes
willbe collected. These are easy to obtain and require little
beforecombustion
intheelemental
analyser.
Organic liquidscan be combusted,but
processing
liquidscontaining large
ofwater would require lyophilisation
so thatthewater traps on
quantities
the elemental analyzer are not overloaded.
As these samples may have significantly higheri4C
concentration
than thosenormallyanalysed, separate laboratory
will be required
forreception,
cataloging andencapsulation

For bio-medicalsarnples,ofthismaterial

time can be allocated to sample preparation,
so a wider
variety ofi4C
Typicalbio-medicaiapplications include
the use of1al)elled
compounds
fbrtracingmetabolic pathways taken by particularcomponentsof these compounds
throughcomplexsystems.
A comprehensive
reviewof AMS
biomedical applications
andtechniques isprovidedby Vogel [1].
AMS not only permitsthe use of much lower levelsof i4C
labelling
10s to IOOs of nCi rather than 100s of pCi for eonventional
testing),itcan(typicallyaiternatively
facilitate
testswith reduced quantities
ofthe compound
thatmust be administered.
samplescanmore

be analysed.

This latteradvantage

is beginningto be exploited

developmentof new drugs.Ifthe amountby pharmaceuticalcompanies

in theofa drugto be administered is1OO times Iowerthan
the levelconsideredagencies
will permittests to be carried
toxic, regulatoryout directlyon
human subjects to determinethe rates of absorption or elimination from the body,before
extensive
animaltestingtakes piace. This technique, known as microdosing,can significantly
reducethe cost and time required fbrthe development
drugs.The 1argescale animalof new
testingrequired often does not adequately
theavailability,
kineticsor dynamics of thepredict
compounds
in the human system.
Microdosingallows such factorsto be assessed beforethe
animal testing and human clinical trial stages, thus eliminating theseexpensive
tests forcompounds
which are foundto be unsuitabie,

Reference:
1. J.S.Vogel,Accelerator
mass
71Piespectrometrlyfor human hiochemistT:y;practice andand Methods B172 (2000)
potentiaL NuclearInstruments
pp, 884-891

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