Chromatography Forum

Hoping someone can enlighten me on possible pitfalls I may not be aware of using a DBwax column when most research found todate uses a DB-1 or RTX-1. I use a wax column because it allows me to see all compounds of interest (esters, terpenes etc.) However if I wanted to study terpenes only, what could I be missing if I continue to use a polar column? Thanks.

The only "problem" with polar columns is that they lack the thermal stability of the DB-1 and DB-5 types of columns. It is possible that some compunds may tail so badly on a wax column that you would never see it them, but then again, some very polar compounds chromatograph poorly on a DB-1 orDB-5 column and give nice peaks on a wax column. You can miss things either way. With a polar column you will have a harder time with higer boiling compunds. And,you can not take the column as high to bake off higher boiling stuff off the column.

One minor disadvantage of polar columns is that they are more variable from manufacturer to manufacturer than the usual siloxanes like DB1 and DB5, and so published retention indices cover a wider range - so wide for many compounds that they are pretty much useless for confirming identities.

I have long been convinced that many separations are run on DB5 type columns for no better reason than that they are the ones that are installed when the instruments are delivered.

Peter

Thank you very much Don and Peter for your insight. Currently I am limited by the number of instruments I have. We have just added a second unit to my lab but still in commissioning stage. Once I sign off, I will try out a non-polar type column to see what I am really missing at the end of the run.

you can have a look at GsBP-1 and GsBP-5 column, which are equivalent to DB1 and DB5, but much more cost effectiveness.

I am reminded of an old post of Rod's - something along the lines of "my favorite column to work with is the one that is already installed".

wax columns are also a no for any sort of anaysis with a derivitizing reagent. Otherwise they are really good for compounds with polar groups. They work well for alcohol, diacetyl, acetoin, esters, and free fatty acids especially which front nastily on most siloxane columns.

wax columns are also a no for any sort of anaysis with a derivitizing reagent. .

A very good point - but nearly all derivatizations yield products that can be run on non-polar columns.

Peter