A test of robustness in IIR-RP-HPLC separation of nine priority pollutant phenols

This study presents an example of method validation, applied to an IIR-RP-HPLC method, developed for the separation of nine PPPs (Priority Pollutant Phenols). The parameters of both primary validation (accuracy, precision, response linearity, detection, and quantitation limits,) and of secondary validation (method ruggedness) are evaluated. The glossary used in literature for ruggedness and robustness is discussed. The robustness test is carried out with respect to five chromatographic conditions, both depending on analyst accuracy (concentration of the ion-interaction reagent, concentration of the organic modifier, and pH of the mobile phase) and on instrumentation (column temperature and flow-rate). The effect of the experimental factors is studied by a fractional factorial design and mathematical models are built; that correlate the chromatographic retention to the experimental factors and to their interactions. The cross-validated models can usefully be employed to evaluate for each studied variable the region of acceptable ruggedness for any given confidence level.