What is the difference between Type A and Type B silica?

What is the difference between Type A and Type B silica?

“Type A” is the stuff that was around first, i.e. the older, low-purity silicas. Most “type B” (= high-purity) silicas are newer. Symmetry and Luna are based on a high-purity silica.

What is C18 silica?

C18 Silica Gel (Octadecyl Phase) C18 silica gel is used for the separation of nonpolar to moderately polar compounds such as: Fatty acids, Glycerides, Polycyclic aromatics, Esters (phthalates), Fat-Soluble vitamins, Steroids, Prostaglandins, PTH amino acids.

Which is more polar silica or alumina?

Alumina is a polar column chromatography adsorbent and will give separations by polar interactions. Thus, the mobile phase used will be a non-polar solvent. Silica Gel and Alumina are both polar adsorbents but Silica Gel is less polar than Alumina.

What is C18 in HPLC?

C18 columns are HPLC (high performance liquid chromatography) columns that use a C18 substance as the stationary phase. C18 simply means that the molecules contain 18 carbon atoms, so the other atoms in the molecule can vary, leading to significantly different substances.

Is silica polar or nonpolar?

Silica gel is a polar adsorbent. This allows it to preferentially adsorb other polar materials. When it comes to polarity, materials interact more with like materials. This principle is particularly important to many laboratories, which use silica gel as the stationary phase for column chromatography separations.

What is the difference between silica and alumina?

Silica is recommended for most compounds, but as it is slightly acidic, it preferentially retains basic compounds. Alumina is slightly basic, so will retain acidic compounds more strongly. It is good for separation of components that are weakly or moderately polar and the purification of amines.

Why is silica so polar?

Silica gel, the most commonly used stationary phase, has the empirical formula SiO2. However, at the surface of the silica gel particles, the dangling oxygen atoms are bound to protons. The presence of these hydroxyl groups renders the surface of silica gel highly polar.