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Fused-Core particles have recently been introduced as an alternative to using sub-2-microm particles in chromatographic separations. Fused-Core particles are composed of a 1.7 microm solid core surrounded by a 0.5 microm porous silica layer (d(p) = 2.7 microm) to reduce mass transfer and increase peak efficiency. The performance of two commercially available Fused-Core particles (Advanced Materials Technology Halo C18 and Supelco Ascentis Express C18) was compared with sub-2-microm particles from Waters, Agilent, and Thermo Scientific. Although the peak efficiencies were only approximately 80% of those obtained by the Waters Acquity particles, the 50% lower backpressure allowed columns to be coupled in series to increase peak efficiency to 92,750 plates. The low backpressure and high efficiencies of the Fused-Core particles offer a viable alternative to using sub-2-microm particles and very-high-pressure LC instrumentation.

The evolution of chromatography has led to the reduction in the size of the packing materials used to fabricate HPLC columns. The increase in the backpressure required has led to this technique being referred to as ultrahigh-pressure liquid chromatography (UHPLC) when the column backpressure exceeds 10000 psi (approximately 700 bar). Until recently, columns packed with sub-2-microm materials have generally fitted into two classes; either short (less than 5 cm) columns designed for use on traditional HPLC systems at pressures less than 5000 psi (350 bar), or capillary columns (inner diameters less than 100 microm). By using packing materials with diameters

Four different column packing techniques were used to pack capillary columns for comparison in capillary electrochromatography (CEC); the techniques were slurry pressure packing, using supercritical CO2, electrokinetic packing, and packing with centripetal forces. Capillary columns of 50 μm ID were packed with each technique and evaluated under electrochromatographic conditions. An initial evaluation suggested that among the packing techniques, supercritical CO2 packing and packing with centripetal forces produced the most efficient packed capillaries. However, examining the various protocols in detail revealed that experience of the practitioner and familiarity with packing equipment are critical factors in column fabrication. Upon further investigation of the packing techniques and optimization of the column fabrication protocol, columns packed by the four packing techniques showed similar performance when operated under CEC conditions. Efficiencies of 270,000–300,000 plates/m were observed for 50 μm ID capillary columns packed with 3 μm packing material.

Chromatography using sub-2 microm particles is becoming increasingly popular due to the potential for increased speed, resolution, sensitivity, and peak capacity. To meet the demand, various vendors have re-engineered traditional LC systems to operate at pressures of up to 15000 psi to accommodate the elevated backpressures associated with using sub-2 microm particles. This report investigates and compares the performance of three very high pressure LC (VHPLC) systems: Waters Acquity, Agilent 1200 SL, and Thermo Accela. Specifications for the pump, autosampler, column compartment, detector, and software for each instrument are presented. To assess the chromatographic performance of the three instruments, method development and validation were performed for three pharmaceutical compounds and the results are compared and discussed. The material presented herein serves to highlight the different features of the VHPLC instruments, and assess their suitability for the analysis of pharmaceutical compounds.