I am working on a project to get the best possible separation for a determination of methylsters. I have to use a GC with FID detection and a 25 m column (I have no idea what kind of column it is, something standard I guess).
Does someone have some suggestions for temperatures and temperature-programmes???

Thanks!

Jorim

Jorim,
Before anyone takes a stab at conditions it is essential toknow what the column type is.

Regards,
Mark

As someone who has assayed thousands of samples of C8 to C18 fatty acid methyl esters, I recommend cyanopropyl silicone capillary such as 15 m x 0.53 mm x 0.20um film thickness fused silica Rtx-2330 capillary (Restek #10722). If you have packed column, then a packed-column equivalent such as 6 ft. x 18 " stainless steel packed with 10% SP-2330 on 100/120 Chromosorb W AW (e.g. Supelco #13776). The unsaturated will elute after the saturate of same carbon number. PEG-type columns also work, similar elution pattern. Way back we used DEGS, but that had shorter lifetime.

Mark is quite correct. But since the poster seems to be quite unexperienced I allow the following:

A generic 'full blown', "slow as molasses in January" method will get you started.

Start at the lowest temperature your GC oven will handle well, usually at 40°C, your injector at 175°C, detector at 250°C, a head pressure at 12 psi, a split ratio of 100:1, and an injection volume of 1µL, program the oven at 4°C/min. to the maximum temperature of 225°C and hold as long as you need to hold it until you are satisfied all esters have been eluted.

This should not harm any column you most probably have and get you started. A lot of folks would be glad to give you more information if you would give them a bit more information, like, what esters, what column ID, phase, its thickness, and the concentrations of the solutions you have to analyze.

A little bit more information...

I have to analyze samples of fatty acid methyl esters with an DB-5ms (122-5532) Column (http://www.chem.agilent.com/Scripts/PDS.asp?lPage=1128). There is no possibility to use an other column...

Hopefully there is another way then "slow as molasses in January"..

Thanks already

Jorim,

If you want information in more detail than above then you must specify the ID of the column and the film thickness.

Goodness ! If you had started trying different temperatures and programing the oven, you would have been done by now.

DB-5 type columns can also be used for fatty acid methyl ester assays (it depends how many isomers, etc., you are interested in). In fact, we used an HP-5 column yesterday in a 6890/5972 GCMS, routine temperature program from 70C to 290C at 10C/minute (after brief initial hold), and holding temperature at 290C at end. Be aware that on this type of column that palmitoleic will elute before palmitic, linoleic before oleic, oleic before stearic, etc. as opposed to what I described in earlier post where the saturates eluted first. The FAMEs have decent spectrum so you should have no trouble identifying them. a good source for standards for this is Nu-Chek Prep.