Ruggedness testing of chromatographic methods: selection of factors and levels

The first step in a ruggedness test is the selection of factors to be exami ned and their levels. In this paper, both topics are discussed, thereby com pleting a strategy described earlier. It is demonstrated, by means of some examples, that depending on the formulation (definition) of a factor, infor mation that is physically more or less meaningful is extracted from the exp erimental design results. Among others, the inclusion of the compounds of a buffer and of the components of a mixture in a screening design were exami ned. A general guideline to select the levels of the factors in a ruggednes s test was proposed. Some special cases? i.e. asymmetric intervals around t he nominal level, were also discussed. (C) 1998 Elsevier Science B.V. All r ights reserved.