NUCLEOSHELL core-shell silica phases for HPLC. NUCLEOSHELL Core-shell technology provides. Better resolution at lower back pressure and shorter retention time. Solid core of silicon dioxide. Homogeneous shell of porous silica. Highest efficiency compared to traditional totally porous materials. Particle size 2. 7 µm (core 1. 7 µm); specific surface 130 m2/g. RP 18 and RP 18plus phases are also available with particle size 5 µm (core 3. 8 µm); specific surface 90 m2/g. Lower back pressure also allows use on conventional LC systems. Pressure stability up to 600 bar.