which column is better?

[che313]

HP-5ms
DB-5ms
Rtx-5ms
ZB-5ms

when you look for thier composition youl find them are similar. i.e. 5% Phenyl 95% Dimethylpolysiloxane

but regarding the performance they will be differ.
any one can help me in selecting between those?

[Peter Apps]

Do not be so certain that the performance will differ; the 5% phenyl column is probably the most widely used of all, and all the manufacturers make them to the same chromatographic specification, mainly so that their columns can be used by for all the analyses for which 5% phenyl is specified. I certainly would not bet on my ability to tell any of these apart by looking at a chromatogram.

Peter

[darber42]

What kind of analysis are you using this for? I've never used an HP or DB-5ms column. The chromatography on the Rtx-5 from Restek is fantastic. Although if you're running alot of dirty samples and you're calibrating for acid compounds you'll be changing the column every month. The ZB-5 is pretty rugged and the chromatography is OK. Pretty much your standard work horse.

[che313]

My analysis is drugs in body fluids (urine or blood) extracted either liquid- liquid or spe and dervatize with BSTFA.

[DR]

If you have the luxury of trying more than one out for yourself, examine the initial peak shapes for each column. See how long one each lasts, compare prices... Performance should be close as these columns are pretty much a standard commodity, so price and longevity differences, while small, can be worth while deciding factors.

If you have no such luxury, ask around among those who have more extensive experience running your types of samples.

[JackC]

One thing you need to consider is the selectivity of those columns. For example, the DB-5MS is a silphenylene type of column (where the phenyl is inserted in the backbone of the phase) versus the pendant phenyl types of the Rtx-5MS and HP-5MS. While the vendors do indeed try to "tune" the selectivities to be the same for these columns, they aren't. I can give you two examples: you can separate m- and p-xylene on the silphenylene column (admittedly with a long run time), but you can't do this on the 5% phenyl pendant column. The other example involves separating 2378 dioxin and 2378 furan from interfering congeners with a 5% silphenylene column; can't be done with a 5% pendant phenyl.

Don't forget the Rxi-5ms from Restek, which is new and advertised to be extremely inert, which may be important for your drug analyses at lower levels. Also, consider a guard column, either attached with a connector, or integral to the analytical column, based on your sample description.

[Goonie]

We use the ZB-5MS here for SVOCs. I love it. Good sensitivity and it lasts quite a long time given that the samples aren't too dirty.