Ruggedness tests for a high-performance liquid Chromatographic assay: Comparison of an evaluation at two and three levels by using two-level Plackett-Burman designs

Ruggedness tests are performed on a high-performance liquid Chromatographic assay for a drug substance. For this purpose two-level Plackett-Burman designs are executed. The factors selected are tested at two and three levels. Significant effects of factors are determined graphically and statistically. For the latter purpose experimental error is estimated from dummy factor effects. The use of other error estimates, as for instance the variance from replicate nominal experiments, as an alternative for the dummies was also examined. The dummy factor effects were found suitable to estimate the experimental error in a Plackett-Burman design. Appropriate replicate injections at nominal levels could be an alternative. Testing at three levels gives more detailed information about the behaviour of a response in function of the factors. It was also found that not only the effects on qualitative responses should be considered but those on quantitative ones as well in order to be able to make a full interpretation concerning the ruggedness of the method.