Particular Developments

Abstract

IntroductionThis Chapter is concerned with quality and chemical analysis. While it can be shown that the required quality as expressed in terms of sensitivity, speed of analysis etc. is, to some extent, dependent on the particular application for which the analysis is used, in all situations these factors need to be known and features such as accuracy and precision should be as good as can be achieved. Thus, how can the quality of an analysis be measured, how can good quality be achieved, and how can good quality be maintained?Reference materials play an essential role in answering those aspects of these quality issues that relate particularly to accuracy and precision although they are also relevant to related concepts such as traceability, trueness and uncertainty ( I S 0 1993, Kristiansen and Christensen 1998). In the use of reference materials (RMs) for these purposes, a clear distinction is made between certified and non-certified reference materials. Highly characterized certified (or standard) reference materials (CRMs, SRMs), with analyte concentrations carefully defined using techniques which afford the very best accuracy, in laboratories with experience and expertise in this type of work, are extremely valuable items. They are also extremely costly. Much of the work to be described here is achieved with well prepared, stable, homogeneous materials where the analyte concentrations are unknown or are given by less rigorous protocols, and are not claimed to be certified. Nevertheless, as shown below, for those applications where such materials are readily available, either from commercial suppliers or as home-produced reagents, they have equally important €unctions when looking at analyhcal quality.A further distinction is made between pure solutions and matrix-based RMs. The former are available for many organic and inorganic analytes, with certified concentrations, but their role in quality control and assessment is limited. They may be used for the preparation of calibration solutions for a particular measurement but more usually these materials represent the base for traceability, through secondary