Can someone explain to me the following terms:

Carbon Loading. Advantages to higher/lower carbon load?

Endcapped vs. non-endcapped. Advantages/disadvantages? Why do I care of silanols are endcapped? For that matter, what is a silanol?

What is the difference between a cyano-, phenyl, amine, and silica packing material?

I'm a technician just transferred to an anlytical division and need clarification on these items as I will be the primary person responsible for ordering columns and consumables. Many thanks. This forum is great!

Is this question too hard? Geeesh, this is like waiting on election results :)

Hi Darby,
The most common and widely used LC columns have various functional groups bonded to a silica base. An 18 carbon chain is by far the most commonly bonded group, hence the term "C18". Other functional groups can be bonded to the base silica include groups like -cyano, phenyl, amines, etc. as well as different lengths of carbon chains (C4, C8) giving rise to the different column types you asked about. Carbon load refers to how much carbon is actualy bonded to the silica, and is loosely dependant on, among other things, pore size, particle size, types of bonding techniques, etc. More carbon load usually means more retention. Bonding takes place at silanol sites (Si-OH). Not all the silanol sites on the base silica can be bonded due to steric hindrance. Leftover silanols can have adverse mixed mechanism efects on a separation, manifested in peak broadening or tailing. Therefore an attempt is made to supress their contributuion by endcapping them. Endcapping is done by bonding a smaller group after the functional group is added, (usually a methyl) that is not sterically hindered.
It is hard to go into much more detail here in this forum, so I recomend two good books to help you along in your new job, Practical HPLC Method Development, by Snyder, Kirkland and Glajch, published by Wiley Interscience, and HPLC Columns, By Neue, also published by Wiley.
Good Luck!!