PRECISION OF 14 C DATING IN GLIWICE RADIOCARBON LABORATORY. FIRI PROGRAMME ANNA PAZDUR, MARIUSZ FOGTMAN, ADAM MICHCZYÑSKI and JACEK PAWLYTA Department of Radioisotopes, Institute of Physics, Silesian University of Technology, Krzywoustego 2, 44-100 Gliwice, Poland (e-mail: pazdur@polsl.gliwice.pl) Abstract: Abstract: Abstract: Abstract: Abstract: In this paper the precision and accuracy of radiocarbon dating in Gliwice Radio- carbon Laboratory on the background of intercomparision programs is discussed. Here are briefly presented results of individual comparisons between laboratories from eight coun- tries and three international intercomparison programmes: ISC Programme (1986), TIRI Programme (1994) and FIRI Programme (1999). Moreover the short description of Gliwice Radiocarbon Laboratory is presented. The main stress is laid on the description of FIRI Programme – types of samples included in Programme and methods of calculation of con- sensus values, but first of all the participation of our Laboratory in the programme is pre- sented: pretreatment procedures of samples, results obtained in Gliwice and statistical analy- sis of these results. The most important conclusion, which may be drawn from this paper, is that Gliwice Radiocarbon Laboratory dating results are not biased by systematic error. Key words ey words ey words ey words ey words: RADIOCARBON DATING, INTERCOMPARISON, LOW RADIOACTIVITY MEASUREMENTS GEOCHRONOMETRIA Vol. 22, pp 27-40, 2003 – Journal on Methods and Applications of Absolute Chronology 1. INTRODUCTION Intercomparison Programs (IP) history Presently there are above three hundred laboratories all over the world which take advantage of 14 C dating. There are three measurement techniques used in 14 C con- centration determination: – gas proportional counters (GPC) which uses propor- tional counters filled by CO 2 or methane as a counting medium, – liquid scintillation counting (LSC) or rather liquid scin- tillation beta spectrometry which uses benzene as a count- ing medium and diluent of a solid state scintillator, – accelerator mass spectrometry (AMS) which uses atom counting approach for 14 C concentration determi- nation. Scientists are pursuing to unification of results ob- tained with use of all these methods for the sake of pre- treatment, age or activity determination and interpreta- tion of results. This is the reason for introducing Intercomparison Programs (IP). The first comparison between laboratories took place in the 70’s. At the same time all 14 C laboratories in UK carried out a precision control. In 1980 Glasgow Labora- tory initiated the first International Radiocarbon Intercomparison Program. The International Collaborative Study program (ICS) was established during XII International Radiocarbon Conference in Trondheim in 1986 (Pazdur et al., 1990). This program was coordinated by a group from Glasgow University. ICS was split into three parts and 60 labora- tories took part in this program. 16 samples were sent to every laboratory within the confines of ICS and some of the samples were the same, but that information wasn’t known to the laboratories. The next program took place in May of 1990. 137 labo- ratories took part in IAEA (International Atomic Energy Agency) coordinated program. Laboratories made activ- ity/age detrmination for 5 samples (carbonates, cellulose, woods and sucrose). In all 69 results: 38 were obtained by LSC, 25 by GPC and 6 by AMS technique. A summary of the results is given in Table 1. The Third International Radiocarbon Intercompa- rison (TIRI) started in 1994. About 60 laboratories sent the results of 14 C dating of 13 samples. A description of these samples and the consensus values are presented in Table 2. The latest comparison program was the Fourth Inter- national Radiocarbon Intercomparison (FIRI). This pro- gram was managed by Department of Statistics, Glasgow University. Ten samples were sent to each of the partici- pating 14 C laboratories in September 1999 and the results from the measurements were collected in the end of Au- gust 2000 (Scott, 1999). The description of the FIRI samples is presented in chapter four of this paper.