1. What is the biggest difference between ordinary HPLC silica columns and Silica-C™?



2. you use the Silica-C™ columns and a Normal Phase Gradient method?



3. I expect a more predictable retention time with Silica-C columns?



4. Does the Silica-C™ column have any carbon in it?



5. Are these columns stable?



6. Most acids and bases are not effective when the organic content of the mobile phase goes too high. Since I am interested to use the Cogent columns in ANP, what can I do to adequately "acidify" the mobile phase when organic is higher than 40%?
   
   
7. How do I use Methyl Phosphonic Acid in my mobile phase?
   
   
8. Is Methyl Phosphonic Acid compatible with UV and MS detectors?

1. What is the biggest difference between ordinary HPLC silica columns and Silica-C™? [top]
The biggest difference is the surface and how it will benefit you. The dominance of silicon hydride (Si-H) groups instead of the “Silanol Group” (Si-OH) common to all irregular, type A & B silica based previous phases changes the general character of the column; solvents will adsorb and desorb differently.

Your separations may or may not be similar when upgrading from ordinary silica to Silica-C™ as this will often depend on the chromatographic conditions you chose to use with the columns. You may want to develop method conditions that utilize the full power of the Silica-C™ columns.

The greatest benefit to Silica-C™ is that when using it for normal phase, you do not need to control the moisture of your mobile phase solvents to control retention times. Also, since the Silica-C™ column does not have a strong association with water, these columns last longer and equilibrate easier.

In general, these columns are more robust, more versatile (can be used for Aqueous Normal Phase) and more convenient than ordinary silica columns.

2. Can you use the Silica-C™ columns and a Normal Phase Gradient method? [top]
Yes, although this is not easy with ordinary silica columns due to solvent demixing & water uptake, the Silica-C™ column is not limited by this.

3. Can I expect a more predictable retention time with Silica-C columns? [top]
Yes, if you develop a method that is optimized with the Cogent Silica-C™ columns compared with an ordinary silica column, the retention times are generally much more reproducible. The reason is most likely that when using ordinary silica columns the uptake of water changes from run to run and the retention often changes. Since the Silica-C column does not take up water, this phenomena does not take place.

4. Does the Silica-C™ column have any carbon in it? [top]
No, the Cogent Silica-C™ column is made completely of Silicon, hydrogen and oxygen. The apparent reverse phase retention you may observe is most likely aqueous normal phase retention.

5. Are these columns stable? [top]
Yes, we have done extensive testing in our labs around the world and in conjunction with customers and have proven that the Cogent Silica-C™ columns are stable even in the presence of water. However, these columns are designed and specified for Normal Phase and Aqueous Normal Phase HPLC and not for Reverse Phase.

6. Most acids and bases are not effective when the organic content of the mobile phase goes too high. Since I am interested to use the Cogent columns in ANP, what can I do to adequately "acidify" the mobile phase when organic is higher than 40%? [top]
We have had some good success with methyl phosphonic acid. It remains soluble in acetonitrile content as high as 96%. This might help when some compounds are retaining in ANP but the peak shape needs to be tightened up a bit.

7.How do I use Methyl Phosphonic Acid in my mobile phase? [top]
You could add 1ml/L into the mobile phase. Add more or less as desired.

8.Is Methyl Phosphonic Acid compatible with UV and MS detectors? [top]
Yes, Methyl Phosphonic Acid, when used in dilute conditions as described above, is UV transparent and is volatile. Therefore you can use it with UV or MS detectors.