Rapid development of core–shell column technology: Accurate measurements of the intrinsic column efficiency of narrow-bore columns packed with 4.6 down to 1.3 μm superficially porous particles

• The apparent HETPs of 31 columns packed with 4 brands of shell particles were measured.
• The method used is based on the plot of the apparent HETPs versus the reciprocal of (1 + k′)2.
• The validated method provides the true extra-column volume variance of the instrument.
• Optimum reduced plate heights increase from 1.6 to 1.9 for particle sizes between 4.6 and 1.3 μm.
• This confirms that wide-bore columns provide better efficiencies than narrow-bore columns.

The intrinsic heights equivalent to a theoretical plate (HETPs) of 31 narrow-bore and wide-bore columns packed with four different brands of core–shell particles were accurately measured on an optimized vHPLC instrument (1290 Infinity system) that has an extra-column volume variance of 13.6 ± 0.3 μL2. These results were derived from the slopes of the linear plots of the apparent plate heights of each column versus the reciprocal of (1 + k′)2 for seven homologous compounds with a linear regression coefficient larger than 0.999. The results show that the kinetic performance of narrow-bore columns packed with core–shell particles increases almost linearly with decreasing particle diameter. The optimum reduced plate heights increase slightly from 1.6 to 1.9 with decreasing particle sizes from 4.6 to 1.3 μm. This confirms that wide-bore columns provide better efficiencies than narrow-bore columns.