Introduction to sampling

People is more and more affected by heterogeneous materials, with complex s patial distribution (biology, ecology, quality for use). Qualitative as wel l as quantitative measurement efficacy depends on both the relevance of the measured dimension, and the representativeness of the analysed fraction. Sampling and sample adaptation to on-line analyser, or to laboratory analys is, concerning application testing or sample storage, must agree with corre ction rules, in order to reduce bias risk, to decrease non-systematic error s, and to allow total error estimation. Every case needs a particular treatment. Critical factors are the actual ob jective, the heterogeneity of both constitution and distribution scares, th e lot size, and the spatial disposition of the lot to be handled. particulate materials are discussed and compared with molecular materials, to enlighten some fundamental notions such as: Sampling by number or by weight. Liberation parameter. Weight to be sampled (M-E). Increments to be collected (N). Sampling design. Static or dynamic lot presentation. Analytical result conversion into lot estimation. The eminent multidiscipli nary character of the sampling process is highlighted. The Analyst has to c ertify correct methods for the entire process and to assume responsability. Sampling is easier to realize when early designed, during the engineering conception. The sampling practice is nowadays impossible to be appreciated as entirely satisfactory. improvements are necessary, not only with gases and natural m aterials, but specially with particulate materials, concerning theoretical bases as well as reglementation and apparatus performance.