Chromatography Forum

Hello,

many of our applications need Merck columns (LiChrospher RP-18 and LiChrospher RP Select B). These are available with particle sizes of 5 µm. Is there any company where also columns with this Merck material are available, but with particles of 2.5, 3 or 3.5 µm in order to enable a pure geometric transfer?

Thank you very much for each answer.

Florian

Both of those are "old" packings which have been on the market for over 20 years. As far as I know, Merck only ever made them in the 5 micron particle size.

Your best bet would be to look at one of the column selectivity databases on the USP web site:
http://www.usp.org/USPNF/columnsDB.html
to find a reasonably close substitute that may be available in a smaller size. Given the age of the material and the advances in silica technology, I'm not sure you can find a close selectivity match in a newer (smaller particle) packing.

Full ACK to Tom's answer with one addition:
Merck offers "Superspher" columns which is afaik nothing else than LiChrospher with 4µm particle size. Both RP18 and Select B are available. Not really small particles, but you might get at least a bit faster

probably you can find a newer column instead of lichrosphere that will work very much the same for most applications
i would go for something of today with 15 or 17% carbon load, since today columns are end capped and with low metal content

for the select B things are a little more complicated. this column had very poor batch to batch reproducability.
today ,merck to solve this sale their master batch select B.
it was their first attempt at creating a low metal content column, by performing some sort of wash to the silica. this was before the type 2 columns came out.
it is a C-8, with a very small pore volume of 60A, but a very small surface area on comparison, with 11.5% carbon loading
at first i would try a standard C-8 with about the same surface area and about the same C% loading.