Plackett-Burman experimental plan

The most important alternative to the fractional factorial experimental plans are Plackett-Burman plans (31). With these, plans are now available that show similar characteristics to full and fractional factorial experimental plans in addition, they are definable for all multiples of4 (12, 20, 24,28,...), which are not power-of-two numbers. A disadvantage, as with the fractional factorial experimental plans, is that only a statistical resolution of 111 is given for these experimental plans this means that only main effects can be estimated. A mixing of main effects and interactions carmot easily be determined, since very few show an overlapping of a two-fold reciprocal effect with a main effect thus, misinterpretations can occur in practice [36]. Table 2 shows a Plackett-Burman experimental plan forn= 12. 

For the design of a Plackett-Burman experimental plan for less than 11 factors, the appropriate number of columns are omitted. 

Due to the fact that it is more reasonable for the robustness test of an HP LC method to determine whether a method is robust in relation to small specific changes of the method parameters, instead of making statements about main effects and intreractions as well as their mixing, the Plackett-Burman plans are the most frequently applied experimental plans for the robustness test of an H P LC method. 

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