Improving LC-MS/MS Bioanalytical Quantitation of Oligonucleotides using New High Performance Tandem Quadrupole Mass Spectrometer

Importance of the Topic

The quantification of therapeutic oligonucleotides in biological matrices poses significant challenges due to their size, structural complexity, and low ionization efficiency in negative mode. High sensitivity and reproducibility are essential for pharmacokinetic, toxicology, and preclinical studies.

Objectives and Study Overview

This study aimed to evaluate the performance of the new Waters Xevo TQ Absolute tandem quadrupole mass spectrometer coupled to the ACQUITY Premier UPLC for sensitive, reproducible quantitation of polythymidine oligonucleotide ladder standards (15–35mer) and the phosphorothioated antisense oligonucleotide GEM91 in human plasma.

Methodology

A liquid–liquid extraction procedure using phenol:chloroform:isoamyl alcohol, followed by chloroform cleanup and reconstitution in EDTA, was optimized for recovery and matrix cleanup. Serial dilutions of stock solutions in plasma generated calibration curves from 0.1 to 10000 ng/mL. The UPLC method employed an Oligonucleotide C18 column with a shallow gradient of HFIP/DIPEA mobile phases.

Instrumentation

• Mass spectrometer: Waters Xevo TQ Absolute tandem quadrupole MS
• UPLC system: Waters ACQUITY Premier UPLC
• Column: ACQUITY Premier Oligonucleotide C18, 1.7 µm, 2.1 × 50 mm
• Mobile phases: 100 mM HFIP + 15 mM DIPEA in water (A), 100 mM HFIP + 15 mM DIPEA in 90% acetonitrile (B)
• Flow rate: 0.5 mL/min
• Gradient: 5–22% B over 0–3.5 min

Key Results and Discussion

Calibration curves showed excellent linearity (r2 > 0.99) and reproducibility across three independent runs. The lower limit of quantification was 0.1 ng/mL for GEM91 and polythymidine standards, with accuracy and precision within ±20% at LLOQ and ±15% at other levels. Sensitivity decreased with increasing oligonucleotide length but remained sub-nanogram for the 35mer. The use of MaxPeak High Performance Surfaces mitigated metal adsorption, enhancing signal stability.

Benefits and Practical Applications

• Low ng/mL sensitivity supports quantitation in pharmacokinetic and preclinical studies
• Wide dynamic range (0.1–10000 ng/mL) covers multiple concentration regimes
• High reproducibility and robustness enable routine LC-MS/MS workflows

Future Trends and Applications

Ongoing improvements in UHPLC column chemistries and advanced surface technologies are expected to further reduce non-specific binding and enhance sensitivity. Integration with automation and high-throughput sample preparation will accelerate oligonucleotide bioanalysis for drug discovery and clinical support.

Conclusion

The Waters Xevo TQ Absolute coupled to ACQUITY Premier UPLC delivers high-performance quantitation of oligonucleotides in plasma, achieving low LLOQs, broad dynamic range, and robust reproducibility, making it a valuable tool for bioanalytical laboratories.

References

• Veeramachineni S, Wrona M. Sensitive LC-MS/MS Bioanalytical Quantitation of Antisense Oligonucleotides. Waters Corp. Application Notes; 720007574, March 2022
• Nguyen JM, Gilar M, Koshel B, Donegan M, MacLean J, Li Z, Lauber MA. Assessing the impact of nonspecific binding on oligonucleotide bioanalysis. Future Science, BIOANALYSIS. 2021;13(16)