Core–shell column Tanaka characterization and additional tests using active pharmaceutical ingredients

In the last decade, core–shell particles have gained more and more attention in fast liquid chromatography separations due to their comparable performance with fully porous sub‐2 μm particles and their significantly lower back pressure. Core–shell particles are made of a solid core surrounded by a shell of classic fully porous material. To embrace the developed core–shell column market and use these columns in pharmaceutical analytical applications, 17 core–shell C₁₈ columns purchased from various vendors with various dimensions (50 mm × 2.1 mm to 100 mm × 3 mm) and particle sizes (1.6–2.7 μm) were characterized using Tanaka test protocols. Furthermore, four selected active pharmaceutical ingredients were chosen as test probes to investigate the batch to batch reproducibility for core–shell columns of particle size 2.6–2.7 μm, with dimension of 100 × 3 mm and columns of particle size 1.6 μm, with dimension 100 × 2.1 mm under isocratic elution. Columns of particle size 2.6–2.7 μm were also tested under gradient elution conditions. To confirm the claimed comparable efficiency of 2.6 μm core–shell particles as sub‐2 μm fully porous particles, column performances of the selected core–shell columns were compared with BEH C₁₈, 1.7 μm, a fully porous column material as well.