Assessment of liquid chromatographic method robustness by use of Plackett-Burman design

Robustness testing is an important part of method validation. Many ideas on robustness testing can be found in the literature, but the most useful approach is application of experimental design. In the work discussed in this paper, Plackett-Burman design was used for robustness testing of an LC method. Robustness was assessed for a previously validated method developed for chromatographic analysis of perindopril tert-butylamine and its impurities. Eleven factors (seven real and four dummies) in twelve experiments were examined. Robustness was assessed by graphical (half-normal probability plots and Pareto charts) and statistical (t -test) methods. For estimation of the standard error of effect (necessary for t -test estimation) calculations based on negligible effects and Dong's algorithm were used at the significance levels alpha = 0.05 and alpha = 0.01. In this way the effect of the factors was completely defined and, furthermore, nonsignificant intervals for significant variables were calculated. Finally, on the basis of the worst-case situation, system-suitability tests were performed and acceptance limits for certain values were calculated.