Shell and small particles; Evaluation of new column technology

The performance of 5 cm long columns packed with shell particles was compared to totally porous sub-2 μm particles in gradient and isocratic elution separations of hormones (dienogest, finasteride, gestodene, levonorgestrel, estradiol, ethinylestradiol, noretistherone acetate, bicalutamide and tibolone). Peak capacities around 140–150 could be achieved in 25 min with the 5 cm long columns. The Ascentis Express column (packed with 2.7 μm shell particles) showed similar efficiency to sub-2 μm particles under gradient conditions. Applying isocratic separation, the column of 2.7 μm shell particles had a reduced plate height minimum of approximately h = 1.6. It was much smaller than obtained with totally porous particles (h ≈ 2.8). The impedance time also proved more favorable with 2.7 μm shell particles than with totally porous particles. The influence of extra-column volume on column efficiency was investigated. The extra-column dispersion of the chromatographic system may cause a shift of the HETP curves.