Improving LC-MS Selectivity for Mesalamine Using Differential Ion Mobility Technology

Significance of the Topic

High selectivity and sensitivity are critical in bioanalytical assays to accurately quantify low levels of analytes such as mesalamine in complex matrices like human plasma. Matrix interferences and background noise often compromise detection limits and reproducibility, driving the need for orthogonal separation techniques before mass spectrometric analysis.

Objectives and Study Overview

This study evaluated the integration of differential ion mobility separation (DMS) via SelexION Technology with multiple reaction monitoring (MRM) on the SCIEX Triple Quad 5500 LC-MS/MS system to improve mesalamine quantitation in human plasma. The primary goals were to reduce matrix interference, enhance signal-to-noise ratio, and achieve a reliable lower limit of quantitation (LLOQ).

Methodology and Instrumentation

• Sample Preparation: Plasma samples were spiked with mesalamine and a deuterated internal standard, derivatized with propionic anhydride, subjected to protein precipitation, evaporated under nitrogen, and reconstituted in mobile phase.
• Chromatography: Shimadzu LC system with Kromasil C18 column (4.6 x 150 mm, 3.5 μm); mobile phase 5 mM ammonium formate (pH 3.0) and methanol (35:65 v/v); isocratic run of 6 minutes; injection volume 10 μL.
• Mass Spectrometry: SCIEX Triple Quad 5500 with SelexION DMS interface and Turbo V source in positive electrospray mode; optimized DMS settings: separation voltage 3900 V, compensation voltage 8.7 V, DMO offset −8.0 V, medium DMS temperature, no chemical modifier.
• Data Processing: Analyst 1.6 and MultiQuant software for acquisition and quantitation.

Key Results and Discussion

Introduction of DMS reduced background noise by approximately twofold, doubling the signal-to-noise ratio at the LLOQ. The calibration curve over the range 10.0–702.0 ng/mL was linear (r=0.9998) using 1/x2 weighting. The derivatized mesalamine eluted at 3.70 minutes in the 6-minute isocratic run. At the LLOQ of 10 ng/mL, the signal-to-noise ratio reached 14.2. Precision (%CV≤6.4) and accuracy (97–102%) at four quality control levels met regulated bioanalytical criteria.

Benefits and Practical Applications

• Enhanced selectivity by orthogonal ion mobility separation reduces the need for extensive sample cleanup.
• Improved sensitivity enables reliable quantitation of low-concentration analytes.
• Streamlined workflow with protein precipitation and short run times lowers analysis cost and increases throughput.

Future Trends and Opportunities

Differential ion mobility is poised to become a routine component of bioanalytical LC-MS workflows, extending to other drug analytes and complex biological matrices. Advances in DMS cell design and software integration will further simplify method development and expand applications in metabolomics and proteomics.

Conclusion

Integrating SelexION DMS with LC-MS/MS significantly improves mesalamine assay performance by reducing matrix effects and enhancing signal quality. The method achieves a robust LLOQ of 10 ng/mL with acceptable precision and accuracy, demonstrating its suitability for regulated bioanalysis.

Reference

1. SCIEX. SelexION Technology: A New Solution to Selectivity Challenges in Quantitative Analysis. RUO-MKT-02-3251-A.
2. van Berkel GJ et al. A Sensitive and Selective LC–Differential Mobility–Mass Spectrometric Analysis of Allopregnanolone and Pregnanolone in Human Plasma. Anal Bioanal Chem. 2013;405:9497-9508.
3. Lim MD et al. Planar Differential Mobility Spectrometer as a Pre-Filter for Atmospheric Pressure Ionization Mass Spectrometry. Int J Mass Spectrom. 2010;298(1-3):45-54.