Oligonucleotide analysis by Ion-pair Reversed Phase Chromatography

Significance of the Topic

The analysis of oligonucleotides plays a crucial role in fields such as biotechnology, gene therapy development and quality control in pharmaceutical production. Reliable separation and quantification of synthetic nucleic acid fragments ensure product consistency, detect impurities and support regulatory compliance.

Objectives and Study Overview

This application note demonstrates a reversed-phase ion-pair UHPLC method for the separation of a series of poly-thymidine oligonucleotides (T6–T30). The goal is to showcase resolution, reproducibility and inertness of the Shim-pack Scepter C18-120 metal-free column coupled with an inert UHPLC system.

Methodology and Instrumentation

Key experimental parameters and equipment include:

• UHPLC System: Nexera XS inert configuration
• Column: Shim-pack Scepter C18-120 [metal-free], 100 mm × 2.1 mm I.D., 3 µm particle size
• Mobile Phase A: 20 mmol/L dibutylammonium acetate (DBAA), pH 6.0
• Mobile Phase B: 20 mmol/L DBAA pH 6.0 : methanol (20 : 80, v/v)
• Gradient Program: 48 % B (0 min) to 68 % B (12 min), ramp to 100 % B (12.01–15 min), re-equilibrate to 48 % B (15.01–20 min)
• Flow Rate: 0.35 mL/min
• Column Temperature: 50 °C
• Injection Volume: 1 µL
• Detection: UV absorbance at 260 nm (SPD-M40 with inert cell)

Main Results and Discussion

The method achieved baseline separation of poly-T oligonucleotides from T6 through T30 within a 12 min gradient. Peak shapes were sharp and symmetric, reflecting the inert metal-free surface of the column and minimized analyte interaction with system components. Resolution between consecutive oligomers was sufficient to distinguish single-nucleotide differences across the series.

Benefits and Practical Applications

This UHPLC ion-pair approach offers:

• High throughput screening of synthetic oligonucleotide products
• Robust performance for quality control in therapeutic oligo manufacturing
• Reduced metal adsorption due to inert pathway and metal-free column hardware
• Reproducible retention times and quantitation for regulatory documentation

Future Trends and Potential Applications

Emerging directions for oligonucleotide analysis include:

• Integration with mass spectrometry detection for sequence confirmation and impurity profiling
• Development of shorter run times through steeper gradients and higher flow rates
• Automation and online sample preparation for increased laboratory efficiency
• Advanced stationary phases tailored for modified nucleic acids, aptamers and siRNA

Conclusion

The Shim-pack Scepter C18-120 metal-free column combined with an inert UHPLC system provides a reliable, high-resolution platform for poly-T oligonucleotide separation. The described ion-pair reversed-phase method enables precise analysis critical to R&D and QC in the oligonucleotide therapeutics industry.

Reference

No external references were cited in the original application note.