<621> Chromatography

Type of Posting: Notice of Adoption of Harmonized Standard
Posting Date: 19-Nov-2021
Official Date: 01-Dec-2022
Expert Committee: General Chapters–Chemical Analysis (GCCA)
Coordinating Pharmacopeia: European Pharmacopeia

The new harmonized standard for <621> Chromatography has been approved by the Pharmacopeial Discussion Group (PDG) as described in its PDG Stage 4 sign-off cover sheet. The chapter has been formally approved by the General Chapters–Chemical Analysis Expert Committee in accordance with the Rules and Procedures of the Council of Experts.

The changes from the current official version of the chapter are:

  • In the beginning of the chapter, added the statement: “Portions of this monograph that are national USP text, and are not part of the harmonized text, are marked with symbols   symbol to specify this fact.


  • The Section Definitions and interpretation of chromatograms is now titled Definitions
  • A method for determine Dwell volume is being added
  • Several definitions used in size-exclusion chromatography are added (Distribution constant, Retention time of an unretained compound, Total mobile phase time)
  • The following definitions are also added:  Plate height, Reduced plate height, Plate number
  • The resolution calculation based on the peak widths at the base line is removed. The Resolution definition and calculation is based now in the peak width at the half of the height.  Also, the formula to calculate resolution in TLC is added
  • The Signal-to-noise ratio definition: The Signal-to-noise ratio was moved from System Suitability section to definition section and the range of the noise used in the calculation is being modified from 5 to 20 peak width.

System Suitability

  • Definitions of System sensitivity and a general requirement for Peak symmetry (0.8-1.8) is being added.

Adjustment to the chromatographic system

  • Allowed adjustments for TLC are being added (Composition of mobile phase, pH, Concentration of salts in buffers, Application volume)
  • A formula to calculate changes in Injection volume is included
  • A new section is added to include all the allowed adjustments in Gradient elution: Particle size adjustment in gradient (see Column dimensions) and Injection volume are being added
  • Gas Chromatography adjustments are listed in a separate sub section


  • The example regarding the use of correction factors when RRF are outside  of the 0.8 – 1.2 range have been removed
  • The term Disregard limit is being replaced by Reporting thresholds;

General Chapter <621> Chromatography will be incorporated into and become official with the USP-NF 2022 Issue 3 (December 1, 2022)

Should you have any questions about this General Chapter, please contact Horacio Pappa (301-816-8319 or hp@usp.org). For any questions about the PDG and its processes, please contact Richard Lew at (240-221-2060 or rll@usp.org).