USP and Ph. Eur.

Allowable adjustments calculator

USP <621> Allowable Adjustments of Chromatographic Conditions – Isocratic Elution

Component As per USP Adjustable from Adjustable to Limit
Mobile Phase Minor Component (<50%) ±30% relative; cannot exceed ±10% absolute adjustment; Cannot be reduced to zero
Mobile Phase pH ±0.2 units
Buffer Concentration (mM) ±10%
Column Temperature (°C) ±10°C
Flow Rate (mL/min) ±50% (at same ID)
As per USP Desired column dimensions
Column Length (mm)
Column Diameter (mm)
Particle Size (µm) *Alternatively (as for the application of particle size adjustment to superficially porous particles), other L/dp combinations can be used provided that the number of theoretical plates (N) is within -25% to +50%
L/Dp % deviated
The column with desired dimension
Relative Flow Rate Suggestion
Injection Volume (µL)

This is just a recommendation

Can be adjusted as much as needed; must be consistent with linearity, precision, and detection requirements

Stationary Phase

No changes of the identity of the substituent recommended.

Choose Phenomenex columns for your analysis

Choose USP column listing