Intercomparison exercises: A requirement for accurate and precise analytical data

External evaluation of laboratory results and procedures can be carried out by participation in intercomparison exercises. the results of the international atomic energy agency - marine environmental laboratory (iaea-mel),monaco intercomparsion exercise iaea-158,marine sediment are presented and discussed in this paper. using four different irradiation protocols instrumental neutron activation analysis (inaa) was used to quantify al,as,br,ce,co,cr,cs,eu,fe,hf,k,la,lu,mn,na,nd,rb,sb,sc,se,sm,ta,tb,th,v,yb and zn in this reference material (rm). iaea-405 (estuarine sediment) and iaea-sl1 (lake sediment) were used as compatible matrix rms for quality assurance (qa) purposes. the z-scores showed our results to be in very good agreement with the iaea certified values. furthermore the iaea placed our laboratory in group 1 for having = 90% of the data with acceptable z-scores.