Improved Peak Shapes for Basic Analytes Using Agilent InfinityLab Poroshell 120 CS-C18 Columns - A comparison to traditional C18 columns with formic acid mobile phase for improved LC/MS sensitivity

Importance of the Topic

The precise separation and detection of basic pharmaceutical compounds in liquid chromatography–mass spectrometry (LC/MS) is essential for accurate quantitation, quality control and regulatory compliance in pharmaceutical development and bioanalysis. Optimized peak shapes enhance resolution, sensitivity and reproducibility, reducing analysis time and resource consumption.

Objectives and Study Overview

This study compares the performance of an Agilent InfinityLab Poroshell 120 CS-C18 charged surface superficially porous particle column against a traditional superficially porous C18 bonded-phase column. The goal was to assess peak shape, resolution and LC/MS sensitivity under simple formic acid mobile phase conditions versus a buffered mobile phase.

Methodology and Instrumentation

Six basic pharmaceutical analytes (atenolol, pindolol, metoprolol, oxprenolol, labetalol and propranolol) were prepared at high (5 µg/mL) and low (50 ng/mL) concentrations. Separations employed a 2.1 × 100 mm, 2.7 µm CS-C18 column or a similarly dimensioned traditional C18 column. A ternary gradient of water (A), acetonitrile (B) and 2% formic acid in water (C) was delivered at 0.4 mL/min with 5% C held constant. Injection volumes were 5 µL for high-level and 0.5 µL for low-level standards, at 30 °C.

Used Instrumentation

• Agilent 1290 Infinity II LC system with reduced dispersion configuration
• Agilent Ultivo triple quadrupole LC/MS with Agilent Jet Stream ESI source
• Agilent InfinityLab Poroshell 120 CS-C18 and traditional superficially porous C18 columns (2.1 × 100 mm, 2.7 µm)

Results and Discussion

The CS-C18 column under simple formic acid conditions produced markedly narrower and sharper peaks compared to the traditional C18 column. Buffering the traditional column with ammonium formate improved peak widths but led to ion suppression, reducing LC/MS sensitivity. At low analyte levels, CS-C18 provided significantly higher signal-to-noise ratios without needing buffer salts.

Benefits and Practical Applications

The charged surface CS-C18 column simplifies method development by removing complex buffering steps, delivering robust, reproducible peak shapes and enhanced sensitivity. Its compatibility with formic acid mobile phases makes it an ideal choice for direct LC/MS analyses in pharmaceutical QA/QC and bioanalytical workflows.

Future Trends and Potential Applications

Advances in charged-surface chemistries are expected to expand the pH stability range, further minimize secondary interactions and broaden applicability to diverse compound classes. Integration with ultrahigh-throughput LC/MS platforms and seamless method transfer between laboratories will drive efficiency in pharmaceutical, clinical and environmental analyses.

Conclusion

The Agilent InfinityLab Poroshell 120 CS-C18 column with formic acid mobile phase demonstrates superior peak shape and sensitivity for basic pharmaceutical analytes compared to a traditional superficially porous C18 column, offering a streamlined, high-performance LC/MS solution.

References

• Gratzfield-Hugsen A.; Naegele E. Maximizing Efficiency Using Agilent InfinityLab Poroshell 120 Columns. Agilent Technologies Application Note, 2016.
• Meyer V.R. Practical High-Performance Liquid Chromatography. 4th Edition; Wiley, 2004; p. 34.