a denotes (semi-)quantitation; b includes azo-glycine, histidine, tyrosine, tert-butyl serine, serine, tryptophan, arginine, pyroglutamic acid, proline, and leucine. PF means Pharmacopeial Forum, which is a free bimonthly online journal in which USP publishes proposed revisions to USP–NF for public review and comment. Note: Current USP-NF describes calibrant as internal standard or reference. Terminology will be updated in the ongoing updates of General Chapters <761> and <1761>.
Reference/Book Chapter: Quantitative NMR in Qulality Control
in Quality Control of Chinese Medicines-Strategies and Methods