Topsil is Welch’s Next Generation Silica, with larger pore size and greater surface area, distinguishing Topsil stationary phases from those in our Ultisil Series.


  • High purity silica (99.99%) with 150Å pore size and 250 m2/g surface area.
  • 12% carbon loading for C18 phase
  • Good for small molecules and peptides.
  • Lower back pressure than Ultisil®.
  • Because of large pore and moderate carbon loading, TopsilTM C18 phase can also be used at 100% aqueous condition without phase collapse.


C18 with lower carbon loading (USP L1). Larger pore size extends the application of this C18 phase into amino acids and peptides (as well as small molecules). 

C8 chemistry (USP L7) provides lower retention than C18, positioning C8 as a selectivity option for reversed phase separations.

Alternative selectivity for phenyl groups (USP L11).

Bare silica (USP L3) with 150Å pore size and 250 m2/g surface area provides the analyst with a viable option for normal phase HPLC on silica.

Topsil NH2 (amino – USP L8) column is useful for mono and disaccharides.

Topsil CN (cyano – USP L10) columns can be used in both normal phase and revered phase modes.