What are the allowed adjustments in USP General Chapter 621 for HPLC Column Parameters and Flow rates in Isocratic Elution? (During Method Development)
Stationary phase: No change of the identity of the substituent (e.g., no replacement of C18 by C8); the other physicochemical characteristics of the stationary phase, i.e., chromatographic support, surface modification and extent of chemical modification must be similar; a change from totally porous particle (TPP) columns to superficially porous particle (SPP) columns is allowed provided the above-mentioned requirements are met. Column dimensions (particle size, length): The particle size and/or length of the column may be modified, provided that the ratio of the column length (L) to the particle size (dp) remains constant or in the range between −25% to +50% of the prescribed L/dp ratio. Adjustments from totally porous to superficially porous particles: For the application of particle-size adjustment from totally porous to superficially porous particles, other combinations of L and dp can be used, provided that the plate number (N) is within −25% to +50%, relative to the pre...