Preparation, Characterization, and Application of New Superficially Porous Silica Particles for Fast HPLC Separation

Importance of the Topic

In modern pharmaceutical and chemical industries, rapid and high-resolution separations are essential for efficient analyses and quality control. Superficially porous silica particles (core–shell particles) reduce diffusion paths and back pressure compared to sub-2 µm fully porous materials, enabling faster HPLC while maintaining high efficiency.

Objectives and Study Overview

This study introduces the development, characterization, and application of new superficially porous silica particles, namely Poroshell 120 (2.7 µm) for small molecules and Poroshell 300 (5 µm) for larger biomolecules. The goals include evaluating chromatographic performance, pressure profiles, efficiency, and sample loadability compared to conventional totally porous particles.

Methodology and Instrumentation

The synthesis yields a nonporous solid core surrounded by a porous shell of controlled thickness. Particle properties were characterized by scanning electron microscopy, pore size distribution via adsorption techniques, and particle size distribution analysis. Chromatographic tests employed columns packed with Poroshell 120 SB-C18 and Poroshell 300 SB-C18 under varied mobile phase compositions, flow rates, gradients, temperatures, and detection at UV wavelengths.

Used Instrumentation

• HPLC system with UV detection compatible with standard 400–600 bar systems
• Columns: 4.6×50 mm, 2.7 µm Poroshell 120 SB-C18; 4.6×50 mm, 1.8 µm RRHT SB-C18; 2.1×75 mm, 5 µm Poroshell 300 SB-C18
• Mobile phases: water/ACN with formic acid, TFA or phosphate buffers
• SEM for morphology and porosimetry for pore volume and surface area

Main Results and Discussion

Poroshell 120 exhibited efficiency comparable to 1.8 µm totally porous particles but with 40–60 % lower back pressure, as confirmed by van Deemter analysis showing reduced A- and C-terms. Fast separations of small molecules (e.g., analgesics) were achieved at high flow rates with minimal pressure increase. Poroshell 300 demonstrated a tenfold reduction in diffusion distance for large biomolecules, enabling rapid peptide and protein separations at elevated flow rates, temperatures, and pressures. Sample loading studies revealed similar overload behavior to totally porous columns, with stable peak shapes up to high analyte concentrations.

Benefits and Practical Applications

• Enhanced throughput in pharmaceutical QA/QC and R&D through shorter run times
• Lower operating pressures enable use on conventional HPLC instruments
• High separation efficiency for both small molecules and large biomolecules
• Reduced solvent consumption and extended column lifetime

Future Trends and Possibilities

Future developments may include engineering of shell thickness and pore size for target analyte classes, integration with UHPLC platforms and mass spectrometry, and expansion into multidimensional separations. Advances in particle design could further reduce back pressure and improve efficiency in complex matrices.

Conclusion

Superficially porous silica particles such as Poroshell 120 and 300 offer a versatile solution for ultra-fast, high-resolution HPLC separations across a broad range of analytes while maintaining manageable back pressures. Their implementation can significantly boost laboratory productivity without requiring specialized high-pressure equipment.

References

• Chen W, Wei T-C, Scone J, Long W, Martosella J. Preparation, Characterization, and Application of New Superficially Porous Silica Particles for Fast HPLC Separation. HPLC2009 Poster, Agilent Technologies; 2009.