Pushing the performance limits of reversed-phase ultra high performance liquid chromatography with 1.3 μm core–shell particles

• Sub-1.7 μm core–shell particles were made.
• Particle morphology and size optimization led to 1.3 μm.
• Practical column dimensions are: 30–75 mm length; 2.1–3 mm i.d.
• Minimum observed HETP values were 2.2 μm.
• Excellent resolving power demonstrated for peptide maps, human urine and crude insulin.

Innovative columns made with very small core–shell particles (1.0–1.4 μm) were investigated over a wide experimental space using state-of-the-art ultra high performance liquid chromatography (UHPLC) instruments. Among the columns tested is one that is now commercially available and is made with 1.3 μm core–shell particles consisting of non-porous cores about 0.9 μm in size and porous shells <0.2 μm thick. This work demonstrated that exceptionally low observed minimum plate heights of 2.2 μm could be obtained using columns packed with 1.3 μm particles, corresponding to a plate count of over 450,000 plates/m. It was shown that only low volume columns allow operation under optimal conditions with current top-of-the-line UHPLC instruments. It was also demonstrated that the loss in performance caused by frictional heating effects remains negligible. Finally, the practical utility of these columns was confirmed with several real-world applications requiring extreme resolving power (i.e. peptide mapping, sample typical of metabolomic studies and crude human insulin). The performance achieved was compared to that of a reference UHPLC column packed with 1.7 μm fully porous particles. The column packed with 1.3 μm particles gave peak capacity values that were 20–40% higher than the reference column for the same analysis time.