High-throughput and reliable assessments of the ionization constant of monoprotic organic acids through an arginine based mixed mode HPLC

Giacomo Russo; Ardiana Kajtazi; Maura Vallaro; Pieter Surmont; Giuseppe Ermondi; Scott Anderson; Lucia Grumetto; Giulia Caron; Frédéric Lynen

doi:10.1016/j.jpba.2023.115604

High-throughput and reliable assessments of the ionization constant of monoprotic organic acids through an arginine based mixed mode HPLC

J Pharm Biomed Anal. 2023 Oct 25:235:115604. doi: 10.1016/j.jpba.2023.115604. Epub 2023 Jul 25.

Authors

Giacomo Russo¹, Ardiana Kajtazi², Maura Vallaro³, Pieter Surmont², Giuseppe Ermondi³, Scott Anderson⁴, Lucia Grumetto⁵, Giulia Caron³, Frédéric Lynen²

Affiliations

¹ School of Applied Sciences, Sighthill Campus, Edinburgh Napier University, 9 Sighthill Ct, EH11 4BN Edinburgh, United Kingdom. Electronic address: g.russo@napier.ac.uk.
² Separation Science Group, Department of Organic and Macromolecular Chemistry, Ghent University, Krijgslaan 281 S4bis, B-9000 Ghent, Belgium.
³ CASSMedChem Research Group, Molecular Biotechnology and Health Sciences Department, University of Turin, piazza Nizza 44 bis 10126 Turin, Italy.
⁴ Regis Technologies Inc., 8210 Austin Ave, Morton Grove, IL 60053, USA.
⁵ Department of Pharmacy, School of Medicine and Surgery, University of Naples Federico II, Via D. Montesano, 49, I-80131 Naples, Italy.

PMID: 37531733
DOI: 10.1016/j.jpba.2023.115604

Abstract

The charge state of a molecule is the single most prominent attribute ruling out its interactions with the surrounding environment. In a previous study, the retention of acids on the new Celeris™ Arginine (ARG) column was found to be predominantly driven by electrostatics and, specifically, their charge state. Therefore, we analysed 41 compounds in liquid chromatography with ultraviolet detection to study possible relationships between the analytical retention on this phase and the pK_a of the acidic solutes. Highly significant relationships were observed indicating either a linear (r² = 0.86) or a quadratic (r²= 0.89) trend. To improve the throughput of the method, this was transferred to LC mass spectrometry, allowing the analysis of a molecule every 3 mins. The developed method was found to be fast, reliable, accurate, easily automatable and simple to set up. Finally, the analytical column's being industrially manufactured and commercially available offers broad applicability.

Keywords: Acidity; Arginine stationary phase; Dissociation constant; High throughput analysis; PKa assessment.

MeSH terms

Arginine*
Chromatography, High Pressure Liquid / methods
Chromatography, Liquid / methods
Hydrogen-Ion Concentration
Mass Spectrometry
Organic Chemicals*

Substances

Arginine
Organic Chemicals