The European Directorate for the Quality of Medicines & HealthCare (EDQM) is proud to highlight the remarkable progress made in 2023 on five general chapters of the European Pharmacopoeia (Ph. Eur.) that cover procedures for powder characterisation. The three revised and two newly elaborated texts add further state-of-the-art methods to the Ph. Eur.
Four of the general chapters have just been published in Ph. Eur. Supplement 11.5 with an implementation date of 1 July 2024. These texts also represent a significant milestone in international harmonisation efforts because they include a general chapter newly elaborated by the Pharmacopoeial Discussion Group (PDG), two revisions that are in the formal PDG harmonisation programme and a text produced through bilateral harmonisation work.
Particle size analysis by dynamic light scattering (2.9.50) is the first general chapter drafted from scratch by the PDG. It provides a detailed description of dynamic light scattering (DLS), a technique used to determine the hydrodynamic size of particles in the submicron range. It covers the principles of this well-established technique and provides information about the typical measuring system and the test procedure itself. This new general chapter will be particularly useful for the characterisation of nanomedicines which are in the focus of the newly expanded NANO working party.
The work on the two revised – also PDG harmonised – general chapters, Bulk density of powders (2.9.34) and Powder flow (2.9.36), was also conducted in collaboration with the Japanese Pharmacopoeia (JP) and the United States Pharmacopeia (USP) as part of the PDG work plan. The definitions of tapped and untapped bulk density in Bulk density of powders have been revised for enhanced clarity. In addition, the dimensions of the apparatus used in Method 2 have been aligned with those given in ISO 3923-2:1981. The general chapter Powder flow has been modified to incorporate, for example, the classification of shear cells into translational and rotational types, with many other changes including to reflect the revised general chapter 2.9.34.
Another revised general chapter published in Ph. Eur. Supplement 11.5 is Density of solids (2.2.42), which was harmonised bilaterally with the USP. This chapter has undergone a major overhaul to introduce the theoretical density classification based on intra- and inter-particular pores. The term “true density” has been removed from this text to avoid any potential confusion concerning its meaning as it is used inconsistently in the current literature.
The new Ph. Eur. general chapter Particle size and shape determination by image analysis (2.9.48) was already published in Ph. Eur. Supplement 11.3 and is to be implemented by stakeholders as of 1 January 2024. The text describes the principle of image analysis for both static and dynamic techniques and covers the equipment and the test procedure used.
The publication of these general chapters in the Ph. Eur. reflects the fruitful collaboration between pharmacopoeias over the past years.
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