Reference Mtls for the Stable Isotopes of Light Elements (IAEA TECDOC-825)

159 Pages·1995·10.76 MB·English

IAEA-TECDOC-825
Reference and
intercomparison materialsrof
stable isotopes of light elements
Proceeda inc fogosn sultants meeting
heldn i Vienna 3-1, December 1993
INTERNATIONAL ATOMIC ENERGY AGENCY
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The originating Section of this publication in the IAEA was:
Isotope Hydrology Section
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REFERENCE AND INTERCOMPARISON MATERIALS FOR
STABLE ISOTOPEF LOSI GHT ELEMENTS
IAEA, VIENNA, 1995
IAEA-TECDOC-825
ISSN 1011-^4289
© IAEA, 1995
Printed by the IAEA in Austria
September 1995
FOREWORD
e shtaTble isotope composif tcioohne mical elements van rnieias tural compounds
as a consequence of the slightly different physico-chemical behaviour of isotopes. In
particular, isotopef osl ight elements, which have helta rgest relative mass differendcnae
therefore alsoe htm ost different behaviour, showe htw idest variationsr oF.i nstance, natural
waters exhibit variatioe hn2tH fso I1H rato it e 1pohu1t :f8o2 Odn,a /16O rato it op1u :1.1,
due to the different evaporation-condensation rate of 'H 16O with respect to 2H1H16O and
2
'H 18O. These variation ranges become even widl ela frni atural compounds containing
2
hydrogen and/or oxygen are considered.
The possibility of measuring the stable isotope relative variations with high
precision, using mass spectrometry, promoted the rise of new fields of research in
geochemistryd na hydrology and, more recently, ni environmental studies.e hT steady
growth of these investigations and of their practical applications has emphasized the need for
high quality isotopic standards and intercomparison samples, with well determined isotopic
compe oihnstit teriroocnfa ,libratif oaonn alytical technid qruneeassu lts among laboratories
Although stable isotope standards have existed for more than three decades, there
was a need to re-examine the whole matter, in view of the expansion of isotope applications
e achnotd ntinuous improvemd ernneatfsi nee mahnte afnloyts tical techniques, which make
it possible to detect smaller and smaller isotopic variations. Just to give an example, up to
rtowe nntey tyears agoa p ,recisf e id±oohe0n tte.1 rnm %iio naf t1io3oCn /12C ratio relative
variatios nagwse nerally considered acceptabd lneeav en goot udwB. i ethhta pplicatiofno
carbon stable isotopes to study the atmospheric carbon dioxide with the aim of improving the
understanding of the global carbon cycle, the long-term analytical precision had to be
increased by an order of magnitude to detect the long term trend of less than 0.02%e per
year, superimposed on the seasonal variations. The laboratories involved in this work had,
and ot hsgrtoilul gohha tvlee n,gthy ched cinknt erraue canonh dsmatlnpya tairfcisao oln s
sampling techniques,n i ordere b ot sure thate ht data obtained ni different placese ra fully
consistent.
e ht ropF ast thirty yearse ,ht International Atomic Energy Agency, throughsti
Sectif oIosn otope Hydrol sobagehye ,n e fahif cetpot lrind veiep arad tdnioiasnt ributifoon
stable isotope referend incnae tercomparison mate ehdrtie arotlefs rminae thiitso ofont opic
composition of natural compounds.
The organization of the Consultants Meeting on Stable Isotope Standards and
Intercomparison Materials held in Vienna from 1 to 3 December 1993, the fifth of this type
(the previous meetings took place in 1966, 1976, 1983 and 1985), called for a review and
a de icshchtuasr afsiocoten ristics, qd uanav elaaehitixylt ias btfiiolnigty standdnarads
intercalibration mn aaas trseoerfs idasnmlsa,e w f mnnoet nea etreodrfs ian lvsi, ief wore cent
developments and applications.
A large part of the discussions was devoted to the new materials prepared for
sulphur isotope analysis and the analytical requirements for highly precise isotopic analysis
of CO . The papers presented at the meeting are assembled in this volume.
2
For the first time, two institutions were represented which are actively engaged in
the field of standardization and intercalibration of isotopic measurements: the Institute for
Reference Materialsd na Measurementse ht fo Commissione ht fo European Communities,
Geel, Belgiume ht dn,a National Instituter of Standardsd na TechnologSU eyht fo
Department of Commerce, Gaithersburg, Maryland, USA. It is hoped that this marks the
begina nn iefnowg , fruitful collaboration betwe eIheAd tnt EnhaAes e institutions.
EDITORIAL NOTE
nIpreparing this publicatior onpf ress, e hItsA tfaoEff A have me hpat adpueg es froehmt
original manuscs ersaiauhpue btvtts hhmi eoyiTwrttbsst e n .ode exncper seossasdreidl y reflect those
of the governments of the nominating Member States or of the nominating organizations.
Throughe hotetuxt t namf oeMs ember St earrtaeets ains aethd ey were wse hahteewtnx t
compiled.
The use of particular designations of countries or territories does not imply any judgement by
e hpt ublishere ,ht IAE ehAt lot es,a gal status of such countriesr o territories, of their authoritiedsna
institutioe htdn fo erso limitation of their boundaries.
The mention of names of specific companier sop roducts (whetht oeni rrno dicateds ar egistered)
y i onntienntnfartt iianoiogm nep n el y pcdrsoboonepa ssrtrieu r tetas drhoiyo unrl dights ,
endorsemer noret commende pahtat inroote n IhoAtf EA.
The authors are responsible for having obtained the necessary permission for the IAEA to
reproduce, translate or use material from sources already protected by copyrights.
CONTENTS
eSmuhmete mtfinoargy ...................................................................7........ .
Standards and intercomparison materials distributed by the International Atomic
Energy Agency for stable isotope measurements ........................................... 13
. RGonfian. tWSintii, chl. eKRr, ozanski
Repof rtsoitnagb le carbon, hydd oronxgyaegne ,n isotopic abundances........1...3....... .
T.B. Coplen
Audit of VSMOW distributed by the United States National Institute of Standards
and Technology ........................................................................5...3........ .
T.B. Coplen, J. Hopple
Sulphur isotope standards .................................................................9...3...... .
B.W. Robinson
Variae thisotu nnlfisu r isotope compoT Ds..iCt.i. of.o.n. ..............................7.4...
G. Beaudoin, B.E.. TMTo. hDyRi le uo,mmrI ,eHbnlse .
Compare ihcstoo fonn ventionale -hlSta Odsnea2r -SF methods: Implicatiornofs
6
the sulfur isotope scale ......................................................................9.4.....
G. Beaudoin, B.E. Taylor
Interlaboratory comparisf ooren ference materr ionaiflts rogen-isotope-ratio
measurements ...................................................................................... 51
J.K. Böhlke, T.B. Coplen
Interlaboratory comw pmeaanrit seforor inoca aflsd r bonoxany gen isotope ratio
measurements ...................................................................................... 67
W. Stichler
Carbon, oxd hynygadern ogen isotopic intercompadri fnsfooraun i t
vegetable juices ..............................................................................5..7....
J. Koziet, F. Pichlmayer, A. Rossmann
e hisTotopic compo esGhittr ifooonn ingen GSd -G1na9S -20 p OsutCraen dards 1.8...
2
H.A..]. Meiier
18
A O rm eô peehaot snrout remee hnIt Atfos EA cellulose intercomparison
material IAEA-C3 ................................................................................. 85
W.M. Buhay, B.B. Wolfe, R.J. Elgood, T.W.D. Edwards
f o esUplatinized magnesiums a reagent replacing zinc ni hydrogen isotope
analysis ..........................................................................................7.8...
S. Halas, B. Jasinska
Carbon isotope (14C, 12C) measurements to quantify sources of atmospheric carbon
monoxi nduie rbr ia.an. ......................................................................3.9...
O.A. Klouda, M.V. Connolly
The carbon dioxide isotopic measurement process: Progress at NIST on
measurements, reduction algorithms and standards ......................................... Ill
R.M. Verkouteren, G.A. Klouda, L.A. Currie
High precision stable isotope measurements of atmospheric trace gases .................. 131
C.E. Allison, R.J. Francey
Recommendations for the reporting of stable isotope measurements of carbon and
oxygen in CO gas ................................................................................ 155
2
C.E. Allison, R.J. Francey, H.A. Meijer
Lisf otP articipants .................................................................................36.1.
IAEA d rpenpuboalritcs an tsitooanb sle isotope stad nmdneaaardsu srement
intercomparison ..................................................................................5.61.
SUMMARY OF THE MEETING
n Ithis se uhfmitftm hf aorIyA EA Meen tioSntga ble Isotope Standdanrads
Intercomparison Materie ahlmts, ajor conclusions e rhetrae cdchnoeamd mendations
formulated at the meeting are presented. They are submitted to the community of those
intereste ehdtd nei terminationf os table isotope environmental variationr osvf arious scientific
and technical purposes. Commd penrnoatps osalse ,c horetnt l oocaoltnnuetlddsy inoans
recommf entohdiast iosno p sescttait fbiaulcel s obmiseoettodipn egn reaferenc e
intercomparison materials in general, will be most welcome and useful, and should be
addressed to the IAEA, Section of Isotope Hydrology. They will be brought to the attention
e chootnf suo lwthainwllt s participn aftiue ture IAEA me sehaemtt inne ogss ubd wjneicallt ,
be of help to all national and international institutions involved in the preparation and
distribution of stable isotope reference materials, in formulating working programmes and
defining lines of co-operation and co-ordination.
1. Sulphur isotope reference and intercomparison samples
Early investigators adopted meteoritic sulpn phauirr t,icularf tthrooa itlite (FeS) from
the Canyon Diablo meteorite, as a reference standard for sulphur isotope studies. The choice
wase ahbpta pnsaeorde nt isotopic homogenef iotym eteoritic e sihdutel pdahn tuahrt ait
could have ehts ame isotopic compositioe htpn sa rimordial sulphur, supporte ehtf dyba ct
that its S/ S value is close to the average of terrestrial samples.
Later, however, it was recognized that the sulphur isotopic composition of Canyon
Diablo Troilite (Cs aDh toonT sma)w ogeneous sad esirable: differeo nt0 pcu.e 2fos5 %o
were observed. Tt ohsuinsr p fsraiicsn tignieg ological materials, which rarely have fully
homogeneous isotopic and chemical compositions. Even so, CDT continued to be used as
a primary reference for sulphur isotopes, and this unfortunate continuance has hampered
progressd na agreement among laboratories.
Intercomparisf oorne sulte sbi ms whporoouny vladbe dd opr toimnfge asurement
calibration the sample of chemically pure Ag S, having a homogeneous isotopic composition
calibrated vs. CDT, which was prepared by B.W. Robinson and C.A.M. Brenninkmeijer
(Institute fo Geologicald na Nuclear Sciences, Lower Huttw ,eN Zealand)n i 1987. This
sample has been tested by several laboratories, and is now distributed by IAEA with the code
name IAEA-S-1 (see Appendix). CDT, for obvious reasons, is kept as a reference to express
o34S results.
The following recommendations were formulated at the meeting:
(i) It has been recognized that it is practically impossible to define a very precise value
of ÎAEA-S-1 versus the Canyon Diablo Troilite (CDT) reference standard, simply
because CDT was not isotopically homogeneous and, in addition, has been exhausted
fo arl ong time. Ths iup tsri,o poseo dta dor opIfAt EA-S e-hv1t aluf oe5 34=S
2
-0.30%o vs. a defined, hypothetical V-CDT (where V stands for Vienna, in analogy
with V-SMOd WnVa -PD sBir teI)c. ommended that laboratories re-calibrate their
measurements versus IAEA-S-1 in order to remove ambiguities on the zero of the 634S
scaled na improve intercomparisonf o results.n I reporting their results, laboratories
should specify that the reference is V-CDT, and not CDT, indicating that the
measurements calibratios amwn ade through IAEA-S-1.
34 32
(ii) A new Ag S sample shall be prepared with a <5 S value close to -30%o from 1 kg of
sphalerite (ZnS) supplied. S yb Halas, Maria Curie-Sklodowska University, Lublin,
Poland. B.W. Robins woZenNe, alann pid sri, inciple reado ytp repae rhset ample,
with the support of IAEA. The new sample will be called IAEA-S-3.
w BaeSnO sAample e sphbreapl( ili ia)red wa i<t5h Sg 0 %vkao3l uf-1reo cmo lotse
of spahlerite supplied by S. Halas, Maria Curie-Sklodowska University, Lublin,
Poland. This sample would complement NBS-127, also BaSO , with
T 0 6(= la3aD14v+bS eo2 Crfr0aao.g t3.oe 2sr%vieso ; Hut, 1987). H.R. Krouse,
University of Calgary, Canada, is in principle ready to prepare the sample, with the
support of IAEA. The new sample will be called IAEA-SO-4 (the code SO implies
34
that the sample can be used for sulphur and oxygen isotopes).
2
(iv) The above new samples, together with IAEA-S-1 and IAEA-S-2, should be widely
distributed to practising laboratories, which should report their results to IAEA with
the3 4objective of establishing recommended 04S3 values for IAEA-S-2, IAEA-S-3 and
IAEA-SO-4 vs. IAEA-S-1.
4
(v) The determination of the absolute isotopic ratios and abundances of IAEA-S-1 is
recommended.
4
(vi) The determination of 633S and 536S, in addition to 34S, by SF technique and by
6
thermal ionization mass spectrometry,r of IAEA-S-2, IAEA-S-3d na IAEA-SO-4.sv
IAEA-S-1, shoule dbe ncouraged.
(vii) Consideration shoue ebglhedi tsv toeatnb lishmef noint tercomparison samprloefs
organic sulphur isotope analyses. In fact, the isotopic composition of organic sulphur
is finding inn cpiree tearssoueled um geochemistry, medical sciences, agriculture,
e wihdf e6 Sotr avn ag d lfefuoeoon sndv fe ioensIraw tceuosndturiney ts,ie.re d
43
these stude ihetv dnsaa rietyf o methods used (including recent on-line combustion
techniqus iea stpi)p, ropria otteh ave relevant intercomparison mateerniOals.
difficulty in selecting the chemical compounds for the intercomparison samples is that
different forms of organic sulphur exist in many natural materials, which may differ
considerably in isotopic composition. For instance, in some oils these forms exhibit
up to 20%o difference in 6 S, attesting to their different geochemical histories.
Cystine (melting point 260 °C) and methionine (melting point 282 °C) have been
suggested as possible materials for the establishment of these intercomparison
samples.
2. Other new intercomparison samples
winetNercomparison sar mohpyflders ogen, c daonrxbayogne ,n stable isotope
determinatn iovinars ious categof rcoioems pe osurunagdgr s eposotfsesd ible consideration
at future IAEA meetings. They include:
)i( a-cellulr ohosyfe drogen, card bonoxany ,gen stable isotope variation nwis oAod .
sample of a-cellulose is now available at IAEA with the code name IAEA-C-3,
whichs iu C s4ie1n rodft ercalibratios nip ti: roposedo tc hecs ktii sotopic composition
d nahomogeneityn i, ordeo rt judge whethes i tris uitabn la esia ntercomparison
sample. The o13C of IAEA-C-3 was measured by a number of laboratories for a 14C
intercomparison exe erhcgti rdsneeaa, t majorif toyr esults ranged from -24%oot
-26%o (Rozanski, 1991).
34
(ii) A methane having <52H at about -300 %o vs V-SMOW and 513C at about -60 %o vs
V-PDB A.s ample with these characteriste bia ycavms ailablet a NIST.
(iii) Two carbon dioxide samples to replace NBS-16 and NBS-17, which have been
exhauster odsf everal y weesnaa ermhTs.p les should have approximatele hyst ame
isotopic composition as NBS-16 and NBS-17, the first of which had 5 C = -41.59%o
and 018O = -36.11%o, and the second 013C = -4.45%o and 018O = -18.76%o vs.
V-PDB (Hut, 1987). NIST will consider preparing these samples.
(iv) Two silver phosphate samples having respectively o O of about 0%o and +20%o vs.
V-SMOe buW sor teo,o dfx ygen isotope measuremenn tips hosphates.
Consideration was also given to other light elements, with the following provisional
indications:
w en moN t)i(ercomparison materials were suggestedr of lithiumd na nitrogen isotope
determinations.
(ii) Two certified reference materials (both H BO ), are available for boron isotopes, one
3 3
from NIST (NIST-SRM-951, with B/ B = 4.04362 ± 0.00137), and the other from
IRMM (IRMM-G11, with UB/10B - 4.0443 + 0.0052). NIST-SRM-951 is currently
a re fseuras neebndi ocre on isotope geocha ewemaStiestrr yb .o sreainter icnhied
"B by about 40 %o with respect to NIST-SRM-951.
(iii) IAEA-NO-3 (KNO ), whichs i distributedr of nitrogen isotope measurements
intercomparison, can possibly also serve as intercomparison sample for oxygen in
nitras toteIxsy. gen isotopic composid thinooanm ogeneity e ncbehe oedtcs ked.
3. Determination of the absolute isotopic ratios of reference samples
U 10
The materials used for isotopic measurement calibration vs. the reference standards,
whicr haf osi ncludee ht r,omf ost common light elements, V-SMOW, SLAP, NBS-19dna
IAEA-S-1 need to be fully characterized, i.e. their absolute isotopic ratios must be
determined. n Tprihiin scio pclhtee ca)klli o(ww eh issheothttoe pric ecohmtpo sfitoion
material will change with time, and (ii) to prepare new materials with identical (within the
experimental errors) or very close isotopic ratios, when the present materials are exhausted
or no longer suitable, or if the storage and handling conditions prove to be inadequate for
13
their long-term conservation.
r otFhese purpose ehastb, solute isotopic e rsahatt imfoosp les indicated above must
be determined with an overall error which is equal or better than the best current analytical
!8
precision for relative isotopic difference determinations. Thus, in principle, the error on the
absolute isotopic ratios shouldt on exceed 0.02%o (13C/12C)for carbon, oxygen (18O/16O)dna
sulphur ( S/ S), and 0.2%o for hydrogen ( H/ H). These limits have so far been approached
e habts oonnliluy te 2H/JH ratio determinatf iooVn -SMd OnSaLWA Py bca trurioed
Hageman. la( nte1 970o h)qw, uote errorf so0 .32%d nQoa .56(7x>, respectivele yheT.r rors
quoted by Baertschi (1976) and Li et al. (1988), for the O/ O and the O/ O determination
of V-SMOW, 0.22% and 2.1% respectively, still appear large.
0 0
e haTbsolute isotopic ratie oruas ser odcf orrectiof nor esults from interferencefos
isobaric ionsn i mass spectrometric analysisd n,at hin as sai dditional reasonr of which their
3
34 32 2 1
18 16 17 16
determina ntimiona terialsr omusfeead surement calibrats idioen sirable. Howeehvter ,
accuracies requiren dit his ct aal eesraeae nsoot rdef orm agnitude less than those quoted
above.
The Institute for Reference Materials and Measurements (IRMM) in Geel, Belgium,
is currentlye Aihnvvtoo gnlavdierd o constant re-determination. e Wshamitthe procedure
and equipment, the overall precisions which can be attained on isotopic ratios are: 0.04%o
for 13C/12C, 0.2% for 15N/14N, 18O/16O and 34S/32S, 1%. for "O/16O. It is anticipated that
0
these precisions will improve considerably in the near future; in particular, for 34S/32S the
precision will soon reach 0.0e I4hRn %TpiMro is .nMic iple reao dmty ease uahbrtes olute
isotopic ratioe hst cfo alibration materials listed above ehT.d eterminatione b snacc arried
out in two phases: in the first phase the isotopic ratios will be determined by using the
Avogadre os hepy curtosbo nid cnned egqnid uu saidyrpe nmntheaentt i,c isotopic mixtures.
Calibration materials of other light elements, including Li, B, Si, Cl, whose natural
isotopic variatione rasu sen dig eochemistry, should alse ob considerer odfa ccurate
(re)determination of absolute isotopic ratios. For silicon, it is suggested to determine the
Si/dnSaiS i/ Si ratif ooNs BS-28 (SiO ): this ma etbue srniean acidpl rinciprolfe
calibratiof nos ilicon isotope measurements.
4. Data reduction procedures
For high precision measurements of stable isotope variations, such as those carried
r oaf ttmuoospheric tracee higtn ratoesf edrncsao, mparisof nor esults between laboratories,
there is a need to adopt common procedures of data reduction. The following is therefore
recommended:
e dhatTa reductio )ni p(r30oced2 8u29re y um2bs8oedd ern automated mass spectrometers should
be clearly documented and accessible to the user, in case he wants to change it. At
presee hnstot ftwr aodrfea ta reduction incorporaten cid omputers drivie nhmtg ass
2
spectromes t etioeohacrnfcsto tceme n dspsnuibtaaltei ,on tporonce dsuire
sufficiently documented.
(ii) The data reduction procedure should be based on a single consistent set of
assumptions for:
e h1t3C /)a!(2C, 18O/Î6d nO1a7 O/16O absolute isotopic rae thiVto n-si PDB CO ,
ie .hCet.O obtained from V-PD ytBbr eatment with H PO 100%t a2 5°C,
2 3 4
and
(b) the relationship between 17O and 18O in terrestrial materials.
s i tdI esirableo t agrea enco ommof o ntves aluer soft hese parameters which appeeaht nri
correction e a1hl8gOto/ r1r6iotOhF mre avsht .af ito0lou ,.e0 020883, ban Bsoead ertschi's
vr aVoluf-eS MOW, enricy h3be0d .9% (recommended vaf loVue -P. sDSvMB dOnWa)
0
by another 10.25%o (recommended value for the isotopic fractionation in CO extraction
from CaCO ), seems to be the best assumption. Values for the othei parameters are reported
in papers includn etihd ese proceedings (Allist eoan l., Gonfiant teianr oi lhF.i)g. h
precision isotopic measurementse hc,t omputation procedurr eodf ata reducti eohvt dnnaa lues
adopted for the above parameters should be clearly documented by the authors.
n fIuture, data reduction procedur rgoefas ses other than CO , sucs Nah O, will need
2 2
e bd oetveloped.
10
3
2
2