Obelisc LC Columns with Liquid Separation Cell Technology

Significance of the topic

High-performance liquid chromatography (HPLC) remains a cornerstone in analytical chemistry for separating complex mixtures of polar and nonpolar compounds in pharmaceuticals, environmental, food and biochemical applications. The introduction of liquid separation cell (LiSC™) technology addresses limitations of traditional stationary phases by creating discrete microenvironments within silica pores. This innovation enables multi-mode separations, improved retention of challenging analytes and streamlined method development.

Objectives and study overview

This whitepaper presents the development and performance evaluation of Obelisc™ HPLC columns incorporating LiSC technology. Key aims include:

• Describing the chemical modification underlying LiSC technology.
• Comparing two Obelisc column chemistries (Obelisc R and Obelisc N).
• Demonstrating multi-mode separation capabilities and tunable selectivity.
• Benchmarking retention of polar and nonpolar analytes against conventional columns.

Methodology and instrumentation

LiSC technology is achieved by grafting long hydrophobic or hydrophilic chains bearing fixed charges onto silica pore walls. This creates an internal cell with distinct ionic strength, pH and hydrophobicity. Two column chemistries are evaluated:

• Obelisc R: Cationic groups near the silica surface separated from anionic groups by a hydrophobic propyl chain, yielding reversed-phase character with ionic interactions.
• Obelisc N: Anionic sulfonate groups near the surface separated from cationic groups by a hydrophilic chain, imparting HILIC and ion-exchange behavior.

Typical mobile phases include acetonitrile/water blends with ammonium formate or acetate buffers (pH 3–5) and low-UV-absorption salts. Detection modes include UV (220–270 nm), ELSD and mass spectrometry.

Main results and discussion

Obelisc R displayed strong retention of both hydrophobic and polar compounds, outperforming traditional C18 and AQ-type reversed-phase columns by up to tenfold in capacity factors for polar analytes. Selectivity tuning via organic content and buffer pH enabled reversal of elution order for mixtures of parabens and catecholamines.
Obelisc R also resolved isomeric and polar drugs, amino acids, herbicides (paraquat/diquat) and polar pharmaceuticals under reversed-phase conditions where conventional columns failed.

Obelisc N excelled in HILIC and ion-exchange modes, separating sugars, amino acids, carboxylic acids and glyphosate impurities with baseline resolution. Conformational changes in the hydrophilic chain induced by mobile phase composition and buffer strength offered fine control over selectivity. Obelisc N further permitted simultaneous anion and cation analysis in a single run with ELSD detection.

Benefits and practical applications

• Two-column workflow: Obelisc R and N cover RP, NP, HILIC, ion-exchange and ion-exclusion modes, reducing column inventory.
• Simplified method development with adjustable retention via ACN content, pH and buffer strength.
• High capacity and rapid mass transfer even at low buffer concentrations.
• Compatibility with MS, ELSD and low-UV detection.

Future trends and potential applications

LiSC technology paves the way for next-generation stationary phases offering dynamic microenvironments. Potential avenues include:

• Custom multi-dimensional separations by combining Obelisc phases with orthogonal chemistries.
• Integration with UHPLC formats and sub-2 µm particles for faster, higher-resolution separations.
• Expanding to novel ligands for chiral, affinity and lipidomics applications.
• Automation of in-column selectivity adjustments through gradient-triggered chain conformation changes.

Conclusion

Obelisc HPLC columns utilizing LiSC technology offer a versatile, high-performance solution for complex separations across polar and nonpolar analytes. By mimicking cellular microenvironments within silica pores, they combine multiple retention mechanisms in one stationary phase, simplify method development and deliver superior retention and selectivity compared to conventional columns.

Reference

Data and figures provided by SIELC Technologies, Inc. Laboratory evaluations and comparative studies with commercial columns were conducted in-house.