Recognizing heterogeneous distribution of platinum group elements (PGE) ingeological materials by means of the Re-Os isotope system

The identification of uncertainties caused by sample inhomogeneity, as dist inct from those caused by sample preparation and measurement, is a challeng ing task. Use of chemometric methods to separate and estimate these contrib utions to the combined standard uncertainty of a measurement (u(c)) of an a nalytical result requires complex experiments. The difficulty of platinum g roup element measurement makes this task even more complex. But unless it c an be demonstrated that sample inhomogeneity is the major contributor to th e high variability of an analytical result one should be careful not to mis takenly attribute this to a nugget effect. In this contribution we are able to demonstrate in two special cases that irreproducible results (up to 90% RSD) for analysis of Os and Re in the pg g(-1) to ng g(-1) range are truly caused by a nugget effect and not by inadequacies of the analytical method .