Chemometrics and Standards

Standards are central to the achievement and maintenance of accuracy in trace analysis. This fact is well-known and well-accepted in the international analytical chemical community, where "standards" are generally considered to be Standard Reference Materials (SRMs) or Certified Reference Materials (CRMs). The term, standards, however, is multivalued, as noted recently by a former Director of the National Bureau of Standards [1]. That is, even in our more conventional view of trace analysis, we must consider in addition to standard materials: standard procedures (protocols), standard data (reference data), standard units (SI), standard nomenclature, standard (certified) instruments, and standard tolerances (regulatory standards, specifications, norms) [2]. It is interesting, in light of these several types of "standards" which have some bearing oil accuracy in trace analysis, to consider the possible significance of standards in and for Chemometrics. To pursue this objective, we first must have a common understanding of the meaning of the term, chemometrics, and what significance it may have for accurate trace analysis. A concise definition is given by the subtitle of the volume which resulted from the first NATO Advanced Study Institute on Chemometrics, i.e., "Mathematics and Statistics in Chemistry" [3]. Implications for accuracy, especially accuracy in trace analysis, are immediately evident. That is, wherever mathematical or statistical operations contribute to the experimental design, data evaluation, assumption testing, or quality control for accurate chemical analysis, "chemometric standards" are at least implicitly relevant. The major part of this paper will be devoted to an explicit discussion of such chemometric standards, including case studies drawn from recent research at the National Bureau of Standards. The discussion will be placed in the framework of the Analytical System, or Chemical Measurement Process (CMP), for such a perspective makes it possible to consider logically a "theory of analytical chemistry"; and certainly chemometrics is a very important part of such a theory [4,5]. To set the stage, the next section will include a brief view of the current content of Chemometrics, together with a summary of its history and literature. This article will conclude with a glimpse at the future of chemometrics, with special emphasis on means to achieve increased accuracy in our chemical measurements and increased understanding of the external (physical, biological, geochemical) systems which provide the driving forces for analytical chemistry.