Heterogeneity-the root of all evil (part 1)

摘要

What is in common to all agents along the entire field-to-analysis pathway, e.g. process technicians and engineers, primary samplers, academic and industrial scientists, laboratory personnel, companies, organisations, regulatory bodies and agencies as well as project leaders, project managers, quality managers, supervisors and directors? All are dependent on reliable analytical data to make decisions, which in one way or another do not originate via aliquots alone. There is sampling, a lot of sampling (and sub-sampling), before a relevant, valid aliquot can be delivered to the analytical laboratory. And all sampling has to deal with materials which are heterogeneous at one scale or another (or at all scales), it is vital to understand the characteristics of heterogeneous materials. One form or other of primary sampling is always necessary which must counteract the effects of the sampling target heterogeneity. A total of five sampling errors arise because all sampling processes interact with heterogeneous lots: two arise because of the heterogeneity of the sampling target, and three additional sampling errors are produced by the sampling process itself-the latter if not properly understood and eliminated, which is the role of TOS. This column, and its sequel, introduces the phenomenon and concepts involved in describing, estimating and managing the adverse effects of heterogeneity in sampling.