Simultaneous quantitation of inorganic ions in oligonucleotides using mixed-mode liquid chromatography coupled with a...

The amounts of inorganic ions (e.g. sodium, potassium, magnesium, calcium, chloride, and phosphate) in intrathecally administered oligonucleotide drug products need to be controlled in order to meet the final target formulation composition. During process development, these ions are measured to ensure the solution composition does not change during purification or drug product compounding and to ensure the final drug product targets are achieved. A quantitative method for ion analysis in antisense oligonucleotide (ASO) drugs was developed by mixed-mode anion exchange/cation exchange-hydrophilic interaction liquid chromatography (AEX/CEX-HILIC) with a charged aerosol detector (CAD). This thirteen-minute method measures monovalent and multivalent cations and anions simultaneously. LC separation conditions, CAD parameters, and sample preparation were judiciously optimized to ensure that the method is specific, accurate, precise, linear, robust, and rugged. With this LC-CAD approach, ion analysis for oligonucleotide drugs can be performed in most analytical labs to support drug development.