Page 11 - CuttingEdge April 2023

Key Changes in USP <621>

4. Other Significant Non-Calculation
Changes
• Quantitation (Reporting threshold)
When the related substances test prescribes a limit for
the total of impurities or a qu antitative determination
of an impurity, it is important to choose an appropriate
reporting threshold and appropriate conditions for
Key Changes in USP <621>
the integration of the peak areas. In such tests the
- Future Expectations
reporting threshold, i.e., the limit above which a peak Fig. 2: Chromatogram of the reference solution
is reported, is defined generally 0.05%. The revised
Figure-2: Chromatogram of the reference solution
chapter excludes the disregard limit and threshold Figure-3: Chromatogram of a blank
setting of the data collection system.
• Quantitation [Relative Response Factor (RRF)]
Key Changes in USP <621>
The relative detector respons factor, commonly
- Future Expectations
referred to as relative response factor (RRF), expresses
the sensitivity of a detector for a given substance
relative to a standard substance. In tests for related
When the related substances test prescribes a limit for the total of impurities or a quantitative determination of an impurity, it is important to
substances, any correction factors indicated in the
choose an appropriate reporting threshold and appropriate conditions for the integration of the peak areas. In such tests the reporting threshold,
monograph are applied.
i.e., the limit above which a peak is reported, is defined generally 0.05%. The revised chapter excludes the disregard limit and threshold setting
of the data collection system.
In the previous version of the chapter, it was stated that
• Quantitation [Relative Response Factor (RRF)]
'In tests for impurities for both the external standard
Fig. 3: Chromatogram of a blank
method, when a dilution of the sample solution is
The relative detector response factor, commonly referred to as relative response factor (RRF), expresses the sensitivity of a detector for a given
D. Peak Symmetry
used for comparison, and the normalization procedure,
substance relative to a standard substance. In tests for related substances, any correction factors indicated in the monograph are applied.
In the previous version of the chapter, it was stated that “In tests for
any correction factors indicated in the monograph impurities for both the external standard method, when a dilution of the
Unless otherwise stated, in a test or assay, the symmetry factor (tailing factor) of the peak used for quantification is 0.8–1.8.
are applied (e.g., when the relative response factor is 5. Challenges in Implementation of
sample solution is used for comparison, and the normalization procedure, any correction factors indicated in the monograph are applied (e.g.,
outside the range of 0.8–1.2)'. Revised USP General Chapter <621>
when the relative response factor is outside the range of 0.8–1.2)”.
In the updated chapter, it was stated that ‘in tests for related substances any correction factors indicated in the monograph are applied’.
In the updated chapter, it was stated that ‘in tests for
4. Other Significant Non-Calculation Changes Chromatography
related substances any correction factors indicated in Multiple challenges and suggested solutions are detailed
5. Challenges In Implementation of Revised USP General Chapter <621> Chromatography
the monograph are applied’.
• Quantitation (Reporting threshold) in Table 2.
Multiple challenges and suggested solutions are detailed in Table 2.
Key Changes in USP <621>
- Future Expectations
Parameter Challenges in USP Suggested Solutions Page 17 of 17

Current chromatography softwares contains formulae with a Need to use EP/JP plate count in the

Plate Count (N) constant of 16 with peak Width at tangent approach. chromatography software
Parameter Challenges in USP (or) Suggested Solutions
As per revision, need to use a new equation with constant 5.54 with Use the custom fields with name of USP
peak width at half height. plate number.
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USP resolution formulae in chromatography software won’t match Needs to use USP resolution HH or JP or EP
Resolution (R)
with the requirement formulae
As off now, noise is taking from same injection at distance ≥ 5 times
the width at the half-height of the peak. Need to implement this by creating the
System Sensitivity Proposed to take the noise in a chromatogram obtained after custom field in the sample set to select noise
injection of a blank, observed over a distance equal to 20 times the from a blank.

width at half-height
No limit requirement as off now. The revised General Chapter Verify the current USP monograph test
<621> Chromatography, specifies as ‘Unless otherwise stated, in a methods for the requirement, accordingly
Peak Symmetry
test or assay, the symmetry factory (tailing factor) of the peak used appropriate corrections/actions to be
for quantification is 0.8-1.8. followed
Table 2. Challenges and possible suggested solutions
Table 2. Challenges and Possible Solutions
6. Adjustment of Chromatographic Conditions
April 2023 Spinco Biotech 11
Chromatography adjustments are outlined in Table 3.

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