INTERLABORATORY COMPARISONS - LESSONS LEARNED

Interlaboratory comparisons have been widely used in analytical chemis try and radiochemistry as an important part of ongoing quality assuran ce programs. The C-14 community has been no exception in this respect, and in just under 20 years, there have been a number of significant a nd very extensive interlaboratory trials organized by individual labor atories and the International Atomic Energy Agency (IAEA) to the benef it of the C-14 community (both labs and users) (Otlet et al. 1980; ISG 1982; Scott et al. 1990; Rozanski et al. 1992; Scott et al. 1992; Gul liksen and Scott 1995). The comparisons have varied widely in terms of sample type and preparation, but all have had as their primary goal t he investigation of the comparability of results produced under possib ly quite different laboratory protocols. As techniques have been devel oped and new labs formed, the reference materials created as a result of the intercomparisons have presented an opportunity for checking pro cedures and results. Users have been reassured by the existence of reg ular comparisons as one sign of the concern that laboratories have to ensure highest quality results, but also confused about how to make us e of the results from past exercises in the interpretation of sets of dates from many laboratories. The laboratories have also learned valua ble lessons from participation in such studies. These have included id entification of systematic offsets and additional sources of variation and in studies which have used realistic samples requiring pretreatme nt, chemical synthesis and counting, it has been possible to identify the stage at which such problems have arisen and to quantify the relat ive contributions to the overall variation. In this paper, we will bri efly review the comparisons so far, draw some conclusions from their f indings, and make proposals for the future organization of intercompar isons.