What kind of experimental design for finding and checking robustness of analytical methods?

Checking robustness is to verify the recommended settings of the analytical method. This verification enables also to assess the response variations near the operational point for each factor. Plackett and Burman designs are often proposed for checking analytical method robustness. But these designs must be used carefully. The first precaution is to add several measurements at the central point to estimate the method repeatability and to be sure that the response surface has no curvature. If the response surface presents an important curvature, Plackett and Burman designs are not suitable to check robustness and other experimental designs must be used. In this case, star designs, which are “one factor at a time” designs seems strangely be the best way to verify the robustness of an analytical method.