Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Rapid identification of short oligonucleotide impurities using lithium adduct consolidated MALDI-TOF mass spectrometry



Owen Becette, Anh Tran, Jace Jones, John Marino, Robert Brinson


Nucleic acids are an increasingly popular platform for the development of pharmaceuticals to treat and prevent multiple diseases including those where traditional small molecule and protein-based drug development efforts have failed. Short oligonucleotide therapeutics, which consist of antisense oligonucleotides (ASOs) and short interfering ribonucleic acids (siRNAs), are prepared by solid phase chemical synthesis, which can generate various impuriies that have the potential to lower drug safety and efficacy. Drug substance-related impurities can be especially difficult to identify and characterize. To address this short coming, here we apply lithium adduct consolidation with matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) to afford a simplified, quick, and facile method for identification of a known drug substance impurity, isobutyryl (iBu) groups arising from incomplete deprotection during solid phase synthesis. We further employ high-resolution nuclear magnetic resonance (NMR) spectroscopy to confirm assessment of the iBu impurity. This lithium adduction consolidation method should find general applicability for routine quality assessment of synthetic oligonucleotides in both academic and industrial laboratories.
International Journal of Mass Spectrometry


MALDI TOF MS, NMR fingerprinting, oligonucleotide therapeutics, drug development, impurities, quality attributes, siRNA


Becette, O. , Tran, A. , Jones, J. , Marino, J. and Brinson, R. (2022), Rapid identification of short oligonucleotide impurities using lithium adduct consolidated MALDI-TOF mass spectrometry, International Journal of Mass Spectrometry, [online],, (Accessed June 20, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created August 8, 2022, Updated November 29, 2022