NMR Reveals an Undeclared Constituent in Custom Synthetic Peptides

This report shows how NMR analysis uncovered the unanticipated presence of substantial amounts of mannitol (20 and 43% w/w) as undeclared constituent in two custom synthetic peptides, DR and DRVYI, that were sourced commercially. Quantitative 1H NMR (qHNMR) readily detected the contaminant, even on a 60 MHz benchtop instrument, and quantified the highly polar UV-transparent adulterant. Quantum-mechanical 1H iterative Full Spin Analysis (HiFSA) achieved unambiguous identification of both the mannitol and the peptides and confirmed the quantitative results.The cases show that experimental verification supersedes trust in both pharmaceutical and research QC. They also highlight the promising utility of established high-field and recently re-evolving benchtop qHNMR. The unanticipated findings remind manufacturers and researchers alike about the advantages of including/performing NMR and qNMR with routine CofA documentation and/or verification of research grade chemicals. Especially when done jointly, this can greatly improve confidence in research and help streamline the pharmaceutical QC toolbox.
Source: Journal of Pharmaceutical and Biomedical Analysis - Category: Drugs & Pharmacology Source Type: research