Pardon my ignorance but could anyone tell what is the difference between an end-capped column and a base-deactivated column? References to written information about the subject would be greatly appreciated.

are all the same

I thought end-capping is a technique to make a column base-deactivated.

"Base deactivated" suggests that something deliberate was done to the column to make it less active towards bases. I think this term originated from gas chromatography where KOH was sometimes incorporated in the stationary phases to stop bases tailing.
In HPLC the term is sometimes used to mean "inactive towards bases". One way to achieve this is to use end-capping. End capping means subsequently reacting a silica that has been bonded with octadecylsilyl groups with a smaller silyating agent (eg trimethylchlorosilane)in an attempt to react more silanol groups which are prevented by steric hindrance from reacting with the larger ODS ligands. End-capping is particularly useful for separations of bases above pH 5, where otherwise silanol groups ionise.
However, end-capping is not usually performed just to achieve base deactivation, since it will also remove interactions of silanols with acids. However, end-capping contributes to "base deactivation".

Pure silica columns are considered essential for base analysis, probably because metallic impurities increase silanol acidity. A pure silica column which is endcapped is likely to give good results for bases (and also acids). An impure silica column which is endcapped may not give good results for bases.

Some manufacturers (I believe) have used silylating groups with free amine functionalites in order to end-cap columns in order to deliberately deactive the column towards basic analytes. These seem to be rather unfavoured, because they tend to be irreproducible, and they give poor results for acids.

David

Base deactivated columns? Doesn't this refer to the silica packing having been flushed with dilute mineral acid such as, HCl, prior derivatisation with the ODS group. This flush removes metal ions on the surface of the silica, whose presence otherwise may be responsible for very acidic, highly reactive silanols.

End-capping, see David.

Silica, its chemistry, manufacture of... has been described in a fantastic review by Nawrocki, J.ChromA, 779 (1997) 29-71.

Wouldn't this be an acid deactivated column?

How can I pack HPLC and SPE columns?

I am trying to pack a 10 cm diameter column with SP HP resin but cannot achieve asymmetry factor below 1.8 due to tailing. Does anyone know if a lower asymmetry factor can be achieved with this resin? Or if anyone can offer reasons for tailing and how to solve the problem, please let me know. I'd really appreciate it.

There are a number of causes of tailing but the most common cause of tailing is excessive attractive forces between particles. Resolving the problem is a matter of choosing a slurry solvent that balances attractive and repulsive forces between particles. Ideally, the slurry medium should provide weak attractive forces. With purely repulsive forces, peak fronting will be observed. A good way to pick an ideal slurry solvent is to observe particles under the microscope in the presence of sufficient solvent to allow the particles to move freely beneath the cover slip. If particles "bounce" elastically when they collide, you have excessive repulsive forces. If the particles "stick" together when they collide, you have excessive attractive forces. What you're looking for is a slight hint of stickiness upon collision. Generally, picking the dispersion solvent to optimize these parameters is based on a general understanding of molecular attractions. For example, a C-18 bonded phase will be sticky in a highly polar solvent such as methanol and exhibit repulsive interactions in a highly nonpolar solvent such as hexane. Achieving optimum properties can be accomplished by blending together two solvents to achieve the proper particle association energy or by simply picking a suitable solvent of intermediate properties. For example, depending on the bonded phase, acetone can provide the proper particle association energy.