0000000000139626
AUTHOR
U. Trüdinger
Effect of polystyrene coating on pore, structural and chromatographic properties of silica packings
Abstract A series of mesoporous and macroporous silicas with a mean pore diameter (PD), between 6 and 200 nm were reacted with a copolymer of styrene and vinyl-methyldiethoxysilane. The mass load of coated silicas corresponded to the monolayer capacity of the polymer calculated on the basis of the molecular cross-sectional area, except for the two mesoporous silcias of PD = 6 and 7.5 nm. Depending on the pore size, changes occurred in the specific surface area, as, between the native and the coated product. A comparison of the specific pore volume, νp, of silicas before and after polymer immobilization indicated a major loss of νp for the two mesoporous silicas whereas this effect was much …
Native and modified alumina, titania and zirconia in normal and reversed-phase high-performance liquid chromatography
Chromatographic properties of silica, alumina, titania and zirconia have been investigated in normal phase mode in the separation of test mixtures of basic, neutral and acidic compounds. In contrast to silica the chromatographic behaviour revealed the basic properties of the alumina, titania and zirconia surfaces. Therefore, separation of basic compounds on these packings seems very promising. Lypophilic packings have been synthesized by modification of titania, zirconia and alumina with organosilanes and polymers and tested for the separation of basic compounds and proteins. High hydrolytic stability of the modified packings was observed during separations with strong alkali and acidic elu…
Packing technology, column bed structure and chromatographic performance of 1-2-μm non-porous silicas in high-performance liquid chromatography
This work is aimed at further elucidating the aggregation behaviour of micron- and submicron-size non-porous silicas and the column performance of 1–2-μm C18 silicas in reversed-phase high-performance liquid chromatography of low-molecular weight compounds. It is demonstrated that highly ordered, dense, porous aggregates of such silica beads were obtained by gravity settling and centrifugation. The slurry techniques applied at constant flow-rate and a pressure up to 50 MPa provided less-ordered aggregates, but generated an acceptable performance of columns when 1–2-μm C18 silica beads were employed. To operate columns of 53 mm × 4.6 mm I.D., the maximum flow-rate needs to be ca. 2.5 ml/min …
Porous zirconia and titania as packing materials for high-performance liquid chromatography
Abstract Porous amorphous zirconia (ZrO 2 ) and titania (TiO 2 ) packings were synthesized as rigid microparticulate beads by means of a sol—gel process. Sufficient rigidity and desired mesoporosity of the ZrO 2 and TiO 2 particles were achieved only by a gel hardening process, followed by heat treatment. The mean pore diameter, p d , the specific surface area, a s , and the specific pore volume, ν p , were controlled by the heat treatment. Typical values were p d = 8 nm, a s = 80 m 2 /g and ν p = 0.23 ml/g. ZrO 2 - and TiO 2 -based revesed-phase packings were prepared by subjecting the native materials to a specific activation process and reaction with octadecyltrimethoxysilane. Native ZrO…