The Use of Hydrophilic Interaction Chromatography with Mass Spectrometry Detection for the Separation of Basic Pharmaceuticals and Food Toxins

Significance of the Topic

Hydrophilic interaction chromatography (HILIC) offers complementary selectivity to reversed-phase liquid chromatography (RPLC) for highly polar and basic compounds that elute too rapidly or with poor retention in RPLC. When coupled with mass spectrometric detection, HILIC enhances sensitivity and peak shape, supporting critical applications in pharmaceutical analysis, clinical monitoring and food safety.

Study Objectives and Overview

This work evaluates HILIC versus RPLC for separating the basic drugs paroxetine and ranitidine, and extends the approach to food toxins melamine and cyanuric acid. Goals include comparing retention behavior, assessing gains in MS sensitivity, optimizing mobile phase and sample preparation parameters, and exploring different HILIC stationary phases.

Methodology and Instrumentation

• Columns: RPLC on ZORBAX Eclipse XDB-C18; HILIC on ZORBAX RX-SIL silica, ZORBAX NH2 amino and modified hydride-based phases.
• HPLC: Agilent 1100/1200 series, gradients of acetonitrile and 5–8 mM ammonium salts, flow rates 0.2–0.4 mL/min, temperatures 25–40 °C.
• MS: Agilent LC/MSD Trap and 6410 triple quadrupole, ESI positive/negative mode, SIM for drugs, MRM for food toxins, optimized gas flows, voltages and collision energies.
• Sample prep: Protein precipitation or SPE for serum; acetonitrile extraction or dilution for pet food, wheat gluten and plant protein matrices.

Main Results and Discussion

• HILIC reversed elution order of paroxetine and ranitidine relative to RPLC, improved retention and delivered up to threefold MS sensitivity gain. Linear calibration (r²>0.999) down to sub-ppb levels and limits of detection in the low ppt range were demonstrated.
• Sample solvent composition and injection volume critically affected retention and peak shape; high organic content minimized dispersion.
• Retention times increased with higher acetonitrile fraction and moderate buffer concentration; pH and temperature also influenced selectivity.
• Melamine and cyanuric acid were resolved by HILIC-MRM in pet food and protein matrices at 50–500 ppt spike levels with recoveries of 80–100%, eliminating need for derivatization and GC-MS analysis.
• Comparisons of silica and amino HILIC phases, including serial coupling, showed tunable selectivity for a broad range of polar analytes.

Practical Benefits and Applications

• Improved retention and peak shape for polar, ionizable compounds without derivatization or ion-pair reagents.
• Enhanced electrospray performance and signal intensity thanks to high-organic mobile phases.
• Simplified workflows via direct injection of biological extracts and SPE eluates.
• Orthogonality to RPLC enables two-dimensional separations for complex sample analyses.

Future Trends and Potential Applications

Interest in HILIC continues to grow, with new stationary phases and buffer systems designed for MS compatibility. Research is focusing on better understanding mixed retention mechanisms, reducing equilibration times and improving robustness. Anticipated applications include high-throughput bioanalysis, metabolomics of polar compounds and comprehensive contaminant screening in food and environmental samples.

Conclusion

HILIC-MS/MS provides a robust, versatile platform to analyze highly polar pharmaceuticals and food toxins. It overcomes RPLC retention limitations, enhances detection sensitivity and streamlines sample preparation. With expanding phase chemistries and ease of integration into LC-MS workflows, HILIC is a valuable tool for pharmaceutical, clinical and food safety laboratories.

References

• Majors RE. LCGC Survey 2007.
• Pittcon 2008 Report. LCGC North America, March 2008.
• FDA. GC-MS Screen for the Presence of Melamine, Ammeline, Ammelide & Cyanuric Acid, Version 2, May 2007.