Proposal for new USP Chapter <319> on NMR Block Length Determination

In Pharmacopeial Forum 52(1), a new USP General Chapter, <319> Nuclear Magnetic Resonance Spectroscopy Block Length Determination for Lactide–Glycolide Polymers has been published for comment..

At the end of October 2025, USP had already published a general chapter prospectus outlining the background and rationale for the development of this chapter.

The proposal notes that “block length is a critical property for understanding and controlling the composition and variability of excipients during formulation development, manufacturing, and testing of lactide–glycolide and lactic acid–glycolic acid polymers (PLGs and PLGAs).” The chapter describes a ¹³C nuclear magnetic resonance (¹³C-NMR) method to determine the glycolate block length in lactide–glycolide polymers that are ring-opening copolymers of DL-lactide and glycolide.

The proposal is available free of charge on the Pharmacopeial Forum website, and comments can be submitted until 31 May 2026.