Friends;

I am looking for a supplier of small particle, large pore size silica-based columns. At the present I am using a 1000 A 3um particle column. I would like to increase the efficiency of my separations by going to even smaller particle sizes.

Any information on special supplier for these columns will be very useful.

Thanks;

Benjamin

hello,
i´m just curious, what are your analyts and who is the supplier of 1000A material? is it rp or normal phase?
thanks
jens

Jens;

The analysis is related to large biomolecules. The separations I am using are reversed-phase ones. There are several suppliers of large pore size adsorbents, Diazem, Jordi, Zorbax, etc.

Benjamin

Check what Macherey and Nagel has to offer! They got 4000A material, but I do not remember if they have it in C18 or in 3 micron.

Benjamin,large pore size and small particles will end up in a column packed with "pores" (just kidding). Mechanical stability is the limit. An alternative are small particles without pores. For exclusion range 1.000 to 1,000.000Da we offer such a material. It's called TSKgel Octadecyl-NPR, and it is polymer based, not silica based. And it is a 2,5µm particle. This material was designed for rapid separation if high MW peptides and proteins with high efficiency. Have a look at www.tosohbioscience.com where you also have access to our applications data base. By the way, what is the MW of your large biomolecules? Gerhard

Gerhard;

I have considered using the material you mention for the analysis and purification of peptides, but I have not found the time to do it. The molecules I am dealing with are oligonucleotides in the 4000 Da molecular weight.

I am not looking for fast separations, I am interested in highly efficient ones. Thus far I have not found anything better than silica-based columns for this problems, and probably I have reached the efficiency limit with them (3 micron particles).

My experience tells me that polymer-based materials are not likely to be more efficent in this case. I have experimented with 4 different columns and the results are not encouraging.

Thanks for your comments.

Benjamin

Benjamin, 4000Da is within the MW range of a 2µm silica based material, called TSKgel Super ODS. Exclusion limit is 20.000Da! Did you checked this material also? This material has a 110 A pore size. I guess you also checked the OligoDNA RP column, with high resolution and high efficiency. But this material was developed for up to 500-mer oligonucleotides. You are right that polymer-based materials are not likely to be more efficent for your application. Good luck. Gerhard

4000 Da is not big, it's small. 4 000 000 Da is big...

I use a 75x4.6 mm, 3,5 µm HPLC column for analysis of some (dirty) biological samples. In this moment I use it with a 12.5x4,6 mm, 5µm precolumn. Is there a risk to plug my column? Should I use a 2 µm frit instead of this precolumn?
Thank you!!

Particle size is usually not a problem in such a procedure, but you may look carefully, when you need to replace the precolumn

Dear Benjamin & Gerhard,

There is a syringe filter (See www.argonide.com) that is capable of high rates of flow (velocities of about 1 ml/cm2/sec) while capable of separating virus to 6 or more logs, DNA and certain proteins. We found that if you stack and operate the discs as a column you can achieve high separation factors dependent upon the charge and Van der Waals adhesion of the sorbate. Nucleic acids are also highly absorbed - DNA to about 200 ug/cm2 of filter area and RNA about 2-3 times as much. When we passed a DNA containing solution through the filter, then one layer (1.4 mm thick) of filter it removed about 99.5% nucleic acid. They sent us a sample syringe filter and we were surprised when to find our results were even better than they claim at unusually high flow rates. Very interesting material...

respected sir i would like to know what will be the effective pore size whether it is 100 angstrom or 300A for effective resolution of my peptide sample (MW=900 dalton) in preparative columns

100 A is fine.

Any suggestion on what size exclusion column I should use for separation of a small molecule (~400 Da) and a ball-shaped molecule (~2000 Da)? I tried TSK-Gel super SW 2000 4.6x30cm, 4u column. It didn't work. Does anybody has experience with small molecule size exclusion?

I think the pore size is too large. An Ultrahydrogel 120 column looks to be about right.

Thanks, Uwe Neue. I forgot to mention that the one I used (TSK-Gel one) is 120A. Do you think I should try Ultrahydrogel 120?

Look at the calibration curves! If my memory serves me correctly, the TSG 2000 is too large.
I looked up the calibration curves for the Ultrahydrogel 120, and it fits to where you want to be.