Particulate silica HPLC columns can produce very high pressures and long separation times. In between runs these columns require a lengthy equilibration phase whilst flow rates and column length are limited, writes Dr K Sinz. In summary, particulate columns can seriously limit the number of samples it is possible to analyse.
A new innovative sorbent material consisting of monolithic rods of highly porous metal free silica is now available as Chromolith HPLC Columns. These contain porous rods of polymerised silica. (Pic 1) These silica rods have a bimodal pore structure, which means that the columns possess a combination of very large internal surface area over which chemical adsorption can take place together with significantly higher total porosity. A dense network of macropores, each 2µm in diameter, creates the high porosity. However within the skeletal structure of the rod there is then a further network of mesopores, each 13nm in diameter, which creates the large internal surface area. (Pic 2)
High quality separations can therefore be achieved whilst very high flow rates can be used with only low pressures. With Chromolith columns flow rates of up to 9ml per minute are no problem. In fact the back pressure is so low that multiple columns can be linked in series if required to produce a separating column of up to 100 000 plates. For the first time flow rate can even be used as a variable to improve separation quality or reduce analysis time.
So separations can be achieved in a fraction of the time that a standard column takes. In addition because of the monolithic silica nature of Chromolith columns, packing down of the silica particles or gel bed splitting under high pressure has simply been eliminated. Column reliability and reproducibility are therefore ensured.
ENQUIRY No 67A
Dr. K. Sinz is with Merck KGaA, Darmstadt, Germany. <a href=“http://www.chromolith.com“ target=_blank>www.chromolith.com</a>
