Mixture design—design generation, PLS analysis, and model usage

In this tutorial article, an introduction to the basics of mixture design is provided. The discussion on mixture design is made from the experimenterʹs point of view, rather than from an elaborate theoretical perspective. Much emphasis is placed on `how to thinkʹ when defining a mixture problem, and analyzing the resulting data. Also, a working strategy for mixture experimentation is proposed. This strategy relies heavily on important contributions from the chemometrics research field, notably the impact of the chemometric `modellingʹ philosophy and its multivariate data analytical tools. In order to illustrate the introduced working strategy, two-mixture applications are outlined. The first example deals with tablet manufacturing and, partly, reflects the classical approach to mixture design based on regular mixture regions. The second example concerns the preparation of a good bubble mixture from which children may produce long-lasting bubbles. This application represents a contemporary chemometrics approach to mixture design when (1) the experimental region is irregular and (2) process and mixture factors are varied within the same experimental protocol.