How reliable are radiocarbon laboratories? A report on the Fourth International Radiocarbon Inter-comparison (FIRI) (1998-2001). (Method).

How reliable are radiocarbon laboratories? A report on the Fourth International Radiocarbon Inter-comparison (FIRI) (1998-2001). (Method). Rationale The most recent radiocarbon inter-comparison exercise (FIRI FIRI Fasting Insulin Resistance Index (research tool to gauge an individual's resistance to insulin)FIRI Fishing Industry Research InstituteFIRI Food Industries Research Institute (Vietnam)),completed in 2001, was also the most extensive so far, with 85laboratories participating. The study was designed firstly to assess thecomparability of the results from different laboratories and then toquantify the extent and possible causes of any inter-laboratoryvariation. Radiocarbon dating is universally employed as a dating toolin archaeology, but there is an inevitable diversity of experimentalapproaches within radiocarbon dating facilities and in this situationthe issue of comparability of results amongst laboratories becomesparamount. In keeping with the principles of analytical science,radiocarbon laboratories have always been conscious of the importance ofaccuracy and precision for their reported results i.e. the ethos ofanalytical quality control (QC) which in turn is the foundation for thewider concept of quality assurance (QA). The care and effort given toestablishing and maintaining primary standards and reference materialsexemplify this concern for good quality management within theradiocarbon community. As early as 1989, Long and Kalin (1990) stressed that it wasincumbent on individual radiocarbon laboratories to engage in a formalprogramme of quality assurance (QA) while Polach (1989) noted that theopportunity for internal checking by individual laboratories in routine[sup.14]C measurement was hampered by a lack of suitable quality control(QC) and reference materials. The work reported here describes ongoinginternational efforts by means of a laboratory inter-comparison toassure users of laboratory quality and comparability of measurements andto provide suitable quality control and reference materials. This workbuilds on the previous laboratory inter-comparisons that have takenplace over the last 20 years (ISG ISG Iraq Study GroupISG Iraq Survey GroupISG International Steel GroupISG Integrated Security GatewayISG Information Systems GroupISG Information Systems Group (IBM)ISG Integrated Starter/Generator , 1982; Scott et al, 1991; Rozanski etal, 1992; Gulliksen & Scott, 1995). A substantial effort has been made by the [sup.14]C community todevelop and apply both internal and external QA procedures. FIRIprovides a part of these procedures in the form of an independent checkof laboratory performance. However, it only provides a spot check ofoperational performance at the time it was carried out and does notmeasure consistent performance over a period of time and so should notform the basis of a `league table of laboratory performance'. Thisis why the FIRI results are published without laboratory attribution at��tri��bu��tion?n.1. The act of attributing, especially the act of establishing a particular person as the creator of a work of art.2. . Objectives The specific objectives of the Fourth International RadiocarbonInter-comparison (FIRI) (Bryant et al, 2000) were to provide: * An unambiguous demonstration of the degree of consistency orotherwise among the results obtained, on a routine basis, from differentlaboratories. This information is crucial for both laboratories andprocurers (researchers and funding agencies). * Quantification of the extent of, and identification of, thepossible causes of, any interlaboratory variation. * Direct assessment of the comparability of liquid scintillationcounting Liquid scintillation counting is a standard laboratory method in the life-sciences for measuring radiation from beta-emitting nuclides. Scintillating materials are also used in differently constructed "counters" in many other fields. (LSC LSC Learning and Skills CouncilLSC Legal Services Commission (UK)LSC Legal Services CorporationLSC Lyndon State College (Lyndonville, VT)LSC Learning Skills CouncilLSC Life Safety Code ), gas proportional counting (GPC (1) A PC that uses the Linux-based gOS operating system. See gOS.(2) (GPC Group) Originally the Graphics Performance Characterization committee of the NCGA, the GPC Group is now part of Standard Performance Evaluation Corporation (SPEC) and oversees the following ) and accelerator massspectrometry accelerator mass spectrometryn.Mass spectroscopy in which a particle accelerator is used to disassociate molecules, ionize atoms, and accelerate the ions. (AMS AMS - Andrew Message System ) techniques. * Creation of suitable, well-characterized quality control andreference materials. * Assurance of trace-ability of the measurements and provision ofan independent check on laboratory performance. These objectives are directly related to analytical quality controlby focusing on experimental accuracy, precision and reproducibility asindices for the assessment and inter-comparison of laboratoryperformance. Evidence of an acceptable level of analytical qualitycontrol is the essential precursor for overall quality assurance. Thebasic methodology employed in the inter-comparison was to invitelaboratories to date a series of reference samples so as to comparetheir performances and the performance of different radiocarbon methods. Selection, preparation and testing of control samples The selection and preparation of large samples of homogeneous[sup.14]C activity (uniform age) which can then be sub-divided are vitalcomponents of a successful radiocarbon inter-comparison exercise.Natural materials were sought which were representative of routinelydated materials and whose ages spanned the full range of the applied[sup.14]C timescale. Potential materials that were identified includedwood (if possible with a dendrochronological date), peat, bone, marinecarbonate and grain, together with specific components of samples suchas the cellulose cellulose,chief constituent of the cell walls of plants. Chemically, it is a carbohydrate that is a high molecular weight polysaccharide. Raw cotton is composed of 91% pure cellulose; other important natural sources are flax, hemp, jute, straw, and wood. fraction of wood and the humic acid Noun 1. humic acid - a dark brown humic substance that is soluble in water only at pH values greater than 2; "the half-life of humic acid is measured in centuries"humic substance - an organic residue of decaying organic matter fraction of peat.The degree of preparation varied from a thorough physical mixing (e.g.marine carbonate--turbidite sediment), through grinding and mixing(whole peat), to complete chemical homogenisation Noun 1. homogenisation - the act of making something homogeneous or uniform in composition; "the homogenization of cream"; "the network's homogenization of political news"homogenizationblending, blend - the act of blending components together thoroughly (humic acid extractionfrom peat). All bulk materials were prepared in a single batch, homogenised Adj. 1. homogenised - formed by blending unlike elements especially by reducing one element to particles and dispersing them throughout another substancehomogenizedblended - combined or mixed together so that the constituent parts are indistinguishable andchecked by replicate analyses on eight randomly selected aliquots. Homogeneity HomogeneityThe degree to which items are similar. testing Other than for the dendrochronologically dated wood samples, thebulk samples were tested at different sub-sample sizes (reflecting oneof the key differences between AMS and radiometric measurement). In allcases, two laboratories checked the sample homogeneity. All the sampleswere in good agreement with the exception of the turbidite tur��bi��dite?n.A sedimentary deposit formed by a turbidity current.turbidite?A sedimentary deposit formed by a turbidity current. and themodern cellulose samples. For the turbidite, the difference between thetwo laboratories was later demonstrated to be due to pretreatment pretreatment,n the protocols required before beginning therapy, usually of a diagnostic nature; before treatment.pretreatment estimate,n See predetermination. . Forthe modern cellulose sample, the difference between the two laboratorieswas due to a small error in assessing the modern standard activity onthe part of one laboratory. Notwithstanding these difficulties, theresults of the homogeneity testing indicated that when laboratoriescomplied with specific instructions concerning sample handling andpre-treatment, all of the samples could be considered to be homogeneousand thus suitable for inter-comparison. Tests conducted by the participating laboratories Each laboratory participating in the inter-comparison was invitedto measure a total of ten samples drawn from a set of seven corematerials within a one-year period. These samples are described in Table1. They included four dendro-dated samples from the Belfast and Germanmaster chronologies, to provide an assessment of laboratory accuracy.Three sets of duplicate samples were provided blind (Kauri wood, Belfastdendro-dated wood and Barley mash) to allow an assessment of laboratoryprecision. The reference samples were distributed to over 120 laboratoriesduring 1999 and by the deadline of December 2000, 92 sets of results hadbeen received, with some laboratories submitting more than one set ofresults. The broad geographical distribution the natural arrangements of animals and plants in particular regions or districts.See under Distribution.See also: Distribution Geographic of participatinglaboratories is shown in Table 2, the radiocarbon techniques employed inTable 3 and a list of the participating laboratories can be found inTable 6. Relative performance of laboratories A total of 122 observations out of 1056 (i.e. slightly over 10%)was identified as anomalous (i.e. outliers). From the statisticaldefinition of an outlier outlier/out��li��er/ (out��li-er) an observation so distant from the central mass of the data that it noticeably influences results. outlieran extremely high or low value lying beyond the range of the bulk of the data. , their proportion should have been around 5%.Thus the number of outliers was approximately twice the number thatwould be expected if they were occurring purely by chance. 39laboratories (42%) had at least one result classed as an outlier. Of the39, almost 60% (23) of these had more than one of their results thusclassed and over 20% (9) had five or more such results. The distributionof outliers was uniform over the 10 samples, thus, no single sample-typecontributed the majority of the outliers. Of the 122 outliers, 87% camefrom LSC laboratories. Other sources of variation (pre-treatment, modern standard andbackground material) For the turbidite sample, a significant age difference was observedbetween the acid-leached and the non pre-treated samples. For the wholewood samples, a very small--so practically unimportant, butstatistically significant--effect due to pre-treatment was alsoobserved. There was an indication of an association between the presenceof an outlier and the modern standard used by these laboratories:further analysis indicated that the presence of outliers was linked tothe modern standard used, some laboratories having no access to theprimary standards of NIST (National Institute of Standards & Technology, Washington, DC, www.nist.gov) The standards-defining agency of the U.S. government, formerly the National Bureau of Standards. It is one of three agencies that fall under the Technology Administration (www.technology. OxI and OxII. After omission of outliers,there was then no evidence of a difference, on average, for any sampledue to modern standard or background materials, with the exception ofthe near background sample (Kauri wood). Overall, a relatively small number of laboratories (14%) generatedmore than 60% of the outlying out��ly��ing?adj.Relatively distant or remote from a center or middle: outlying regions.outlyingAdjectivefar away from the main areaAdj. 1. observations, and the majority of theselaboratories use liquid scintillation scintillation/scin��til��la��tion/ (sin?ti-la��shun)1. an emission of sparks.2. a subjective visual sensation, as of seeing sparks.3. techniques (including directabsorption). However, it should be noted that there remain a substantialnumber of liquid scintillation laboratories with none or only oneoutlier. Measures of orecision and accuracy--comparing duplicates Laboratories were asked to measure three pairs of duplicatesamples: A and B (Kauri wood, near background activity), D and F(Belfast wood, around 50 pMC (percent modern carbon)) and G and J(barley mash, at approximately 111 pMC) to allow the assessment oflaboratory precision relative to the quoted errors. The summarystatistics for the differences of the duplicates are shown in Table 4(note that D/F results are given in years BP). This analysis showed that, on average, the difference betweenduplicates is zero (over all laboratories and also for individuallaboratories). However, the magnitude of the difference in someindividual cases was large relative to the quoted errors (and largerthan expected given the interpretation of the quoted error). Theimplication is that, in such cases, a source of variation may not becompletely accounted for in the quoted error. On the other hand,evidence was also observed of agreement between the duplicates, whichwas in fact better than would be expected on the basis of the quotederrors. This corresponds to an underestimation of precision. Theobserved differences were adequately described by the quoted errors forapproximately 50% of the laboratories. Samples of known age Accuracy can only be assessed against known age materials and for[sup.14]C these are typically dendro-dated wood samples, so four suchsamples were included in FIRI. Consensus values (based on an iterative it��er��a��tive?adj.1. Characterized by or involving repetition, recurrence, reiteration, or repetitiousness.2. Grammar Frequentative.Noun 1. procedure involving the calculation of a weighted average (Rozanski etal, 1992)) for the samples are shown in Table 5. A different method,based on reliability analysis, was used for the calculation of theconsensus value for samples A and B. The four dendro-dated wood samples included in the list of coresamples were D and F (duplicates) from the Belfast master chronology anddendro-dated to 3200-3239 BC ([sup.14]C age of 4495 BP); sample I (alsofrom the Belfast master chronology) which has a dendro-date of 3299-3257BC ([sup.14]C age of 4471 BP) and sample H from the German oakchronology which was dendro-dated to 313-294 BC ([sup.14]C age of 2215BP). With respect to the dendrodated samples, it can be observed thatthe consensus values and the average `master' values are such thatthe differences are all within the limits of the quoted errors. Thus,the consensus results are in agreement with the master chronologyresults, so that overall, we can conclude that laboratories are, ingeneral, accurate. For an individual laboratory, the difference (knownage-laboratory measured age) for the dendro-dated samples can also beused to assess accuracy. It was found that the differences weredistributed around zero, with the majority of results lying in the rangeof 100 years. Formal calculations showed that approximately 30% of thelaboratories had a statistically significant offset. Improving quality The reported results from FIRI for each laboratory are in somesenses a summary and therefore do not allow further examination of thecauses of laboratory offsets (beyond that already reported here). Theresponsibility for investigating sources of the offset (and if required,amending procedures) rests with the individual laboratories. We havestudied the effect of the modern standards and the background materialsthat are used by laboratories in their analyses and find no evidencethat these factors make a significant contribution to the overallvariation observed. In-house policies for the definition and use of standards isimportant. The FIRI results demonstrate that there remains a need forstandards and reference materials to which laboratories have readyaccess to allow checking and correction. Five categories of standard canbe defined for application in the ideal situation viz., i) Primary (or modern) standard. The internationally calibrated cal��i��brate?tr.v. cal��i��brat��ed, cal��i��brat��ing, cal��i��brates1. To check, adjust, or determine by comparison with a standard (the graduations of a quantitative measuring instrument): andcertified materials NBS-Ox I and NBS-Ox II. ii) Secondary standards. Internationally recognised materials suchas ANU-sucrose, Chinese--sucrose and the IAEA IAEAInternational Atomic Energy Agency. quality control referenceseries (C1-C8). Reference materials from TIRI Tiri is a not for profit NGO founded in London in 2003 by Fredrik Galtung and Jeremy Pope both of whom were original founders members of Transparency International. Tiri was established as an anti corruption organisation out of the recognition that the time for talking about the and FIRI are now alsoavailable to expand this list. iii) In-house/inter-laboratory QC standards. Materials selected torepresent the type and age of submitted samples. iv) In-house working standard(s). A bulk supply of homogeneousmaterial that is available in sufficient quantity to allow repeated andfrequent analysis. These measurements are intended to monitor andcontrol the reproducibility of the analytical process over time. v) Background standards. To achieve accurate and reproducible work,and especially with samples older than say four half-lives, it isessential to define the appropriate background signal using"[sup.14]C free" (geologically old) material that has achemical composition close to that of the sample. The backgroundmaterial should also be subjected to an identical form of anypre-treatment that is applied to the raw sample. It is clear that programmes such as FIRI are, and will continue tobe, necessary. One plan under consideration is that a majorinter-comparison, such as FIRI, would be organised every four years butthat in each of the three preceding years, a small number of sampleswould be sent to laboratories to be analysed in a short time andfeedback then given. In this way, the `spot-check' nature of FIRIand the lack of continuous monitoring of performance would be remedied.Such a system would have benefits to the participating laboratories andwould also provide a better `quality guarantee' to the usercommunities. All results and a full report on the inter-comparison willappear as a special issue of Radiocarbon in 2003 (Scott et al.,forthcoming). Rewards for the archaeological user The selection by a user of a laboratory to which samples are sentis dependent on a number of factors, including cost and the time takento obtain results. The choice may also be dependent on the samplematerial, on the sample size and on the precision with which the resultis required. Laboratories differ in their capabilities to measure verysmall samples (AMS rather than radiometric); a few laboratories are ableto measure to extremely high precision (<15 years) (onlyradiometric), while specialised pre-treatment procedures for unusualmaterials may only be available in a small number of laboratories. But laboratory selection should also be based on an evaluation ofthe QA performance of the individual laboratory. By the simple fact ofparticipation in a programme such as FIRI, a laboratory is emphasisingits commitment to the quality assurance of its results. As in previousinter-comparisons, although the laboratory attribution in any resultstable is anonymous, a list of the participating laboratories ispublished (Table 6). Further, individual laboratories are encouraged, ifthey wish, to publish and publicise Verb 1. publicise - call attention to; "Please don't advertise the fact that he has AIDS"advertise, advertize, publicizeannounce, denote - make known; make an announcement; "She denoted her feelings clearly" their own performance in theinter-comparison and many do so. Users are also encouraged to asklaboratories about their QA policies and should pay attention tolaboratory participation in inter-comparisons and more specifically tolaboratory use of standards and reference materials (such as TIRI, FIRIand IAEA C1-C8). That said, the FIRI results have emphasised that on average,[sup.14]C laboratories (whether gas proportional, liquid scintillationor accelerator mass spectrometry) are providing accurate and preciseresults. Conclusion The results of the latest FIRI have demonstrated that there are nosignificant differences between the main measurement techniques (gasproportional counting, liquid scintillation counting and acceleratormass spectrometry) but there is evidence from some laboratories of smalllaboratory offsets relative to known age samples. There is also evidencein some cases for over- or under-estimation of measurement precision.Approximately 10% of all results were classified as extreme (outliers)and these results were generated by 14% of the laboratories.Notwithstanding good internal QA procedures, some problems still occurwhich can best be detected by participation in independentinter-comparisons such as FIRI where the results allow individuallaboratories to assess their performance and to take remedial measures.Table 1. Core sample descriptionsCore Sample description FIRI code * Age/ActivityKauri wood A, B Near backgroundMarine turbidite C ~3 half-livesBelfast dendro-dated wood D, F ~1 half-lifeHumic acid E ~2 half-livesBarley mash G, J modernHohenheim dendro-dated wood H < 1 half-lifeBelfast dendro-dated cellulose I ~1 half-life* Code to indicate the material which is being datedTable 2. Geographical distribution of participating laboratoriesGeographical area Number of laboratoriesEurope (EU) 35Europe (non EU) 15North and South America and Canada 16Asia and the Far East 15Australia and New Zealand 4Table 3. Methods appliedMethod Number of laboratories using itLSC (1) 44GPC (2) 19AMS (3) 17Target feeder for AMS (4) 8Direct absorption and LSC (5) 2(1) Liquid scintillation counting.(2) Gas proportional counting.(3) Accelerator mass spectrometry.(4) Laboratories that prepare samples and sendthem to AMS laboratories for measurement.(5) Laboratories that absorb sample carbon in the form ofC[O.sub.2] into a tertiary amine or similar compound andmeasure the activity by LSC (generally a low precision method)Table 4. Descriptive statistics: (Differencesbetween duplicates DF in years BP) Standard Average DeviationSample Number or Mean of Minimum Maximumpair of results difference difference difference differenceAB 54 0.029 pmC 0.214 -0.66 0.53GJ 71 -0.094 pmC 1.085 -4.37 2.76DF 79 17.4 years BP 97.3 -239 310Table 5. Consensus values Consensus valueSample Known age (estimated 1 precision)AB (pMC) - 0.24 pMC (1) (95% CI (0.23 - 0.30))C (yBP) - 18176(10.5) yBP2DF (yBP) 3200-3239BC ([sup.14]C age 4495BP) 4508 (3) yBPE (yBP) - 11780 (7) yBPGJ(pMC) - 110.7 (0.04) pMCH(yBP) 313-294BC ([sup.14]C age 2215BP) 2232(5) yBPI (yBP) 3299-3257BC ([sup.14]C age 4471BP) 4485(5) yBP(1) percent modern carbon; (2) radiocarbonyears before present where present is 1950.Table 6. Laboratories participating in FIRILaboratory name CountryLATYR, La Plata ArgentinaPabellon INGEIS ArgentinaCSIRO, Glen Osmond AustraliaANTARES AMS Centre, ANSTO AustraliaArsenal Research AustriaVERA, Universitat Wien AustriaVRI, Institut fur Radiumforschung Austria und KernphysikIRPA, KIK BelgiumIGSB, Minsk ByelorussiaEIL, University of CanadaWaterlooAECL, Chalk River CanadaGeological Survey of Canada CanadaKyushu Environmental JapanEvaluation AssociationInstitute for Advanced JapanScience, OsakaPalynosurvey Co JapanCCR Nagoya University JapanGakushuin University, Tokyo JapanKyoto Sangyo University JapanSeoul National University KoreaInstitute of Geology, Vilnius LithuaniaRJ van de Graaff Lab, NetherlandsUtrechtCIO Groningen NetherlandsRafter Lab, Institute of New ZealandGeological SciencesUniversity of Waikato New ZealandEHPL-Env, Ontario Hydro CanadaIOEE Chinese Academy of ChinaSciencesRudjer Boskovic Institute CroatiaInstitut fur Fysik, DenmarkUniversity of AarhusInstitute of Geology, Tallinn EstoniaGSF, Espoo FinlandUniversity of Helsinki FinlandIPSN/LMRE, Orsay FranceHIGL, Paris-Sud University FranceTandetron-Gif FranceUniversite Claude Bernard, Lyon FranceUmweltforschungzentrum GermanyLeipzig- HalleLeibniz, Universitat Kiel GermanyIUF, Universitat Koln GermanyUFZ-CER, PRG, Halle GermanyInstitut fur Bodenkunde, GermanyUniversitat HamburgHeidelberg University GermanyDAI, Berlin GermanyIGR, NLB, Hannover GermanyUniversitat Erlangen-Nurnberg GermanyLOIH, Insitiute of Physical GreeceChemistry, DemokritosLOA, Institute of Materials GreeceScience, DemokritosInstitute of Nuclear Research, HAS HungaryPhysical Research Lab, Earth IndiaSciences Div., AhmedabadPhysical Research Lab, IndiaRadiocarbon Dating Lab, AhmedabadBirbal Sahni Institute, Lucknow IndiaCRDIRT, JCPJ, Jakarta IndonesiaUniversity College Dublin IrelandKimmel Center, Weizmann IsraelInstituteRDL, University of Rome ItalyLa SapienzaRadiological Dating Laboratory, NorwayTrondheimSilesian Technical PolandUniversity, GliwiceA & E Museum, Lodz PolandITN-Sacavem PortugalGeological Institute, RAS RussiaGeographical Research, RussiaSt. Petersburg State U.Institute of Geography, RAS RussiaInstitute of Ecology and RussiaEvolution, RASInstitute of History of RussiaMaterial Culture, RASIQFR, Madrid SpainUniversity of Granada SpainFacultad de Quimica, SpainUniversitat de BarcelonaTandem Lab, University of Uppsala SwedenUniversitat Bern SwitzerlandETH, Zurich SwitzerlandDepartment of Geology, NTU TaiwanOffice of Atomic Energy for Peace ThailandSchool of Geosciences, Queens UKUniversity BelfastResearch Lab for Archaeology, UKOxfordSUERC, East Kilbride UKNERC Radiocarbon Lab UKLab of Radioecology, KIEV UkraineUSGS, Reston USABeta Analytic Inc., Florida USANSF Arizona USAGeochron Labs, Cambridge, MA USACAMS/LLNL USANOSAMS WHOI USAINSTAAR, University of USAColorado at BoulderUC Riverside USAISGS, Illinois USA Acknowledgements This work was supported by NERC NERC Natural Environment Research Council (UK)NERC North American Electric Reliability Corporation (Princeton, New Jersey, USA)NERC Northeast Recycling CouncilNERC National Environment Research Council (Grant Ref: GR9/03389) and theEuropean Commission (Grant Ref: SMT (1) (Surface Mount Technology) See surface mount.(2) (Station ManagemenT) An FDDI network management protocol that provides direct management. Only one node requires the software. SMT - Station Management 4-CT98-2265). We also wish to expressour gratitude to Mike Baillie Not to be confused with Mike Baillie, drummer of The SkidsDr Mike Baillie is a Professor Emeritus of Palaeoecology in the School of Archaeology and Palaeoecology at Queen's University of Belfast in Northern Ireland. , Marco Spurk, Roy Switsur, GlengoyneDistilleries, Ganna Zaitseva, Kh Arslanov, John Thomson John Thomson is the name of: John Arthur Thomson (1861-1933), Scottish naturalist John Edgar Thomson (1808–1874), American civil engineer, railroad executive and industrialist John Thomson (actor) (b. and Alan Hogg hoggcastrated male sheep usually 10 to 14 months old. Also used to describe an uncastrated male pig. who provided many of the samples. References BRYANT C, I. CARMI, G. COOK, S. GULLIKSEN, D. HARKNESS, J.HEINEMEIER, E. MCGEE, P. NAYSMITH, G. POSSNERT, M. SCOTT, J. VAN DER DER - Distinguished Encoding Rules PLICHT & M. VAN STRYDONCK. 2002. Sample requirements and design of ainter-laboratory trial for Radiocarbon laboratories. NIMB NIMB Not in My BackyardNIMB No Input Mixing Board (Toshimaru Nakamura)172: 355-359. GULLIKSEN S & E. M. SCOTT. 1995. TIRI report, Radiocarbon37(2): 820-821. ISG, 1982. An inter-laboratory comparison of radiocarbonmeasurements in tree-rings. Nature 198: 619-623. LONG A & R. KALIN. 1990. A suggested quality assurance protocolfor Radiocarbon dating laboratories. Radiocarbon, 32(3): 329-335 POLACH, H. 1989. [sup.14]C CARE. Radiocarbon, 31(3): 422-431. ROZANSKI K, W. STICHLER, R. GONFIANTINI, E.M. SCOTT, R.P. BEUKENS,B. KROMER & J. VAN DER PLICHT. 1992. The IAEA [sup.14]Cintercomparison exercise 1990. Radiocarbon 34(3): 506-519. SCOTT E M, T.C. AITCHISON, D.D. HARKNESS, G.T. COOK & M. S.BAXTER. 1990. An overview of all three stages of the internationalradiocarbon intercomparison. Radiocarbon 32 (3): 309-319. Elisabetta Boaretto (2), Charlotte Bryant (1), Israel Carmi (2),Gordon Cook (3), Steinar Gulliksen (4), Doug Harkness (8), JanHeinemeier (5), John McClure (8), Edward McGee (6), Philip Naysmith (3),Goran Possnert (7), Marian Scott (8) * , Hans van der Plicht (9), Markvan Strydonck (10). 1) NERC Radiocarbon Laboratory, Scotland, 2) Weizmann Institute,Israel, 3) SUERC SUERC Scottish Universities Environmental Research Centre (Universities of Edinburgh and Glasgow), Scotland, 4) NUST NUST National University of Sciences and Technology (Rawalpindi, Pakistan)NUST National University of Sciences and Technology (Zimbabwe)NUST N��cleo de Sa��de do Trabalhador (Portugese), Norway, 5) University of Aarhus HistoryIt was founded in 1928 as Universitetsundervisningen i Jylland ("University Teaching in Jutland") in classrooms rented from the Technical College and a teaching corps consisting of one professor of philosophy and four Readers of Danish, English, German and ,Denmark, 6) University College Dublin, Eire, 7) University of Uppsala,Sweden, 8) University of Glasgow The University of Glasgow (Scottish Gaelic: Oilthigh Ghlaschu, Latin: Universitas Glasguensis) was founded in 1451, in Glasgow, Scotland. , Scotland, 9) University of Groningen Degree programmesBachelor's degree programmesThe Bachelor phase lasts three years and after successful completion of a Bachelor's programme result in a BSc or BA degree. There are a total number of 61 Bachelor degree programmes. ,The Netherlands, 10) KIK KIK Klub Inteligencji Katolickiej (Poland)KIK [not an acronym] Laughing Out Loud (letters adjacent to LOL - keyboarding error)KIK Key Integrity Key , Belgium. * corresponding author: marian@stats.gla.ac.uk Received 6 June 2002; Revised 5 January 2003.