Sampling behavior of multielements in candidate NIST RM 2703 by using neutron activation analysis

Sampling behavior of multielements in candidate NIST RM 2703 and NIST SRM 2702 were characterized at sample sizes of 0.8 to 1.4 mg by instrumental neutron activation analysis(INAA) combining with Ingamells model. The two materials are the same in matrix but different in particle size distribution, the former is finer than the latter. At least 12 elements are confirmed to be homogeneous enough with relative standard sampling uncertainties smaller than 1% at 1 mg sample size level for both materials. The fact that the sampling constants of Dy, Hf, Lu and Sb in RM 2703 are much smaller than in SRM 2702 clearly indicates the influence of particle size distribution on sampling behavior. (authors)