High Speed vs. High Resolution Analyses in HPLC: A Critical Performance Comparison of Column Options Using Poppe and Kinetic Plots

Importance of the Topic

In modern analytical laboratories, balancing separation speed and resolution in high-performance liquid chromatography (HPLC) is essential for efficient workflows. Faster analysis increases sample throughput, while high resolution ensures accurate identification and quantitation of closely eluting compounds. Comparing particle technologies under realistic conditions helps practitioners select the optimal column for their pressure limits and analytical goals.

Objectives and Study Overview

This study critically evaluates two column formats: sub-2 µm fully porous ZORBAX RRHD Eclipse Plus C18 and 2.7 µm superficially porous Poroshell 120 EC-C18. Using theoretical Poppe plots and experimental kinetic measurements, the work assesses each column’s performance across fast (short column) and high-efficiency (long column) separations under controlled temperature and pressure conditions.

Methodology and Instrumentation

A systematic flow study was conducted:

• Van Deemter analysis on alkylphenone probes to derive A, B, C terms and hmin values.
• Transformation of Van Deemter data into Poppe plots to compare plate count (N) and plate‐count‐per‐time (N/t₀) across varying column lengths and pressures.
• Series-connected columns to simulate lengths from 5 cm to 55 cm.

Instrumentation

Agilent 1290 Infinity LC System with 2.1 mm × 50 mm and 2.1 mm × 55 mm columns
Columns:

• ZORBAX RRHD Eclipse Plus C18, 1.8 µm, operated at up to 1000 bar.
• Poroshell 120 EC-C18, 2.7 µm superficially porous, operated at up to 550 bar.

Operating conditions: 40 °C, %ACN adjusted to k′≈6, mobile phase velocity optimized per column.

Main Results and Discussion

The reduced Van Deemter analysis revealed a lower C term and smaller hmin for Poroshell 120, indicating improved mass transfer efficiency. Poppe plots showed:

• Fast (5 cm) separations: both columns achieved comparable N/t₀ values, with Poroshell 120 delivering 5 514 plates at 549 bar versus 6 194 plates at 1003 bar for the 1.8 µm column.
• Long (55 cm) separations: Poroshell 120 generated ~97 000 plates at ~547 bar, while the 1.8 µm column produced ~105 000 plates at ~1001 bar.

Under optimized conditions, Poroshell 120 matches the efficiency of sub-2 µm particles at roughly half the backpressure. Elevated temperature further enhances resolution, particularly for superficially porous particles.

Benefits and Practical Applications

• Poroshell 120 columns offer high efficiency with moderate backpressure, ideal for standard HPLC systems (<600 bar).
• Sub-2 µm fully porous columns deliver peak performance in UHPLC setups capable of 1000 bar or higher.
• Selection depends on laboratory pressure limits, throughput needs, and scalability requirements.

Future Trends and Opportunities

Advances may include evaluation of higher-viscosity solvents such as methanol, development of new superficially porous chemistries, integration of ultra-high-pressure systems, and greener mobile phase alternatives. Further optimization of column temperature and miniaturized formats will expand application scope in pharmaceuticals, environmental testing, and quality control.

Conclusion

Under optimized conditions, 2.7 µm Poroshell 120 superficially porous columns demonstrate comparable separation efficiency to 1.8 µm fully porous columns at significantly lower pressures. For conventional HPLC applications, Poroshell 120 is recommended; for ultra-high-performance needs, sub-2 µm columns remain the top choice in systems rated above 800 bar.