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We are currently making changes to this tool for the updated allowed adjustments, please chat with our technical experts who will be able to provide a recommended method in the meantime.
USP and Ph. Eur. Allowable adjustments calculator

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

ComponentAs per USPAdjustable fromAdjustable toLimit
Mobile Phase Minor Component (<50%)35.3255.32±30% relative; cannot exceed ±10% absolute adjustment;
Cannot be reduced to zero
Mobile Phase pH0.801.20±0.2 units
Buffer Concentration (mM)19.8024.20±10%
Column Temperature (°C)1232±10°C
Flow Rate (mL/min)0.451.35±50% (at same ID)
As per USPDesired 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/Dp50000.0050000.00% deviated
The column with desired dimensionCan be used.0.00%
Relative Flow Rate Suggestion0.901.19
Injection Volume (µL)33

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.

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