Design and evaluation of a dicationic ionic liquid-embedded C18 stationary phase for mixed-mode chromatography

Area of Science:

• Analytical Chemistry
• Chromatography
• Materials Science

Background:

• Traditional chromatography often requires multiple columns or methods for separating diverse chemical compounds.
• Developing versatile stationary phases that can accommodate various separation mechanisms is crucial for efficient analytical workflows.

Purpose of the Study:

• To develop and characterize a novel mixed-mode stationary phase, Sil-DIL-C18, for enhanced chromatographic separations.
• To evaluate the performance of Sil-DIL-C18 compared to conventional columns for a wide range of analytes.
• To elucidate the retention mechanisms governing the separation on the new stationary phase.

Main Methods:

• Covalent embedding of a dicationic dipyridinium ionic liquid within C18 chains on silica.
• Systematic evaluation of chromatographic retention under varying mobile-phase conditions (composition, salt concentration, pH).
• Comparison with conventional Extend-C18 and HILIC Plus columns.
• Quantitative elucidation of retention mechanisms using Abraham's solvation parameter model and Tanaka tests.
• Application to the determination of acetaminophen in pharmaceutical formulations.

Main Results:

• Sil-DIL-C18 demonstrated superior resolution for hydrophobic (alkylbenzenes, PAHs) and polar/ionizable compounds (nucleosides, sulfonamides, alkaloids, organic acids, antipyretic analgesics).
• The column's versatility allowed activation of reversed-phase, hydrophilic, or ion-exchange mechanisms by adjusting mobile-phase composition.
• Embedded dipyridinium moieties improved compatibility with aqueous mobile phases and peak symmetry for basic analytes.
• Retention mechanisms confirmed synergistic multi-modal interactions.
• Excellent retention repeatability was observed.
• Successful application in determining acetaminophen in Tylenol tablets.

Conclusions:

• The novel Sil-DIL-C18 stationary phase offers exceptional versatility and resolution for diverse analytes through tunable mixed-mode chromatography.
• This column overcomes limitations of traditional phases, providing improved peak symmetry and aqueous compatibility.
• Sil-DIL-C18 represents a significant advancement in chromatographic separation technology for both research and pharmaceutical analysis.