<811> Powder Fineness

A harmonized standard for Powder Fineness has been approved by the Pharmacopeial Discussion Group (PDG) as described in its PDG Sign-Off Cover Page. Having reached Stage 6 of the PDG process, the Powder Fineness General Chapter has been formally approved by the USP General Chapters—Physical Analysis Expert Committee in accordance with the Rules and Procedures of the 2010–2015 Council of Experts.

Changes from the existing USP–NF General Chapter include:

  • Omitted from further harmonization the section Sieves for Pharmacopeial Testing, which references USP General Chapters. It is not needed for this chapter as a reference to <786> Particle Size Distribution by Analytical Sieving already exists.
  • Omitted the section Powdered Vegetable and Animal Drugs based on comments that it is irrelevant for harmonization.
  • Omitted the section Air Permeation Method for Determining Fineness of Sub-sieve Size Particles based on comments that it would be better to describe this method separately. This paragraph is no longer referenced in a USP monograph.
  • Defined Classification of Powder Fineness based on sieve opening, as opposed to particle size.
  • Added a column to the table "Classification of Powders by Fineness" to also define the parameters based on cumulative distribution.
  • Eliminated the term "Very Coarse" as it is not used in the EP and JP.
    Sieve openings > 1000 µm were added to the description for "Coarse."

The <811> Powder Fineness General Chapter will be incorporated into and become official with USP 35–NF 30.

Should you have any questions about the <811> Powder Fineness General Chapter, please contact Kevin Moore (301-816-8369 or ktm@usp.org). For any questions about the PDG and its processes, please see Pharmacopeial Harmonization Group or contact Richard Lew at (240-221-2060 or rll@usp.org).