Seek help on Split inlet liner selection for FAME on HP 5890

[tiggeria]

I am setting up an old HP 5890 for FAME assay.

My test runs have two problems: loading discrimination and ghost peaks. After further testing, I determined that the liner and/or the inlet need to be cleaned/changed.

I am here seeking opinions on selecting a liner for this assay. what is the best liner technically? My main concern is the high boiling point component discrimination and contamination.

Currently, the GC has a HP/Agilent liner with cup design, filled with 10% OV-1 on Chromosorb, and also a bit glass wool on top, as shown here at http://www.sigmaaldrich.com/catalog/pro ... &region=US.

I will be most interested in FAME compositions from C16 to C26, and mainly the heavy ones.

Column: OmegaWax (Polyethylene Glycol coated) 30m x 0.25mm x 0.25um
Sample: FAME in hexane ( the organic liquid phase from a direct transesterification tube)
Injection vol.: 0.5 micro liter manually.
Carrier gas: helium at 2 ml/min @ 80C.
Injector temperature: 250 C
FID detector temperature: 260C
Split flowrate: 35 ml/min @ room temp
Purge flowrate: 3 ml/min@ room temp
Air flowrate: 415 ml/min@ room temp
Hydrogen fule rate: 30 min/min@ room temp
Nitrogen makeup flowrate: 38 min/min@ room temp
Temp: 80C, 2min --> 40C/min to 170C --> hold at 170C for 5 min --> 2 C/min to 220C --> hold at 220C for 25 min.


I searched the forum, and found this old post mentioned a FocusLiner liner at posting.php?mode=reply&f=2&t=8494.

Also, this article recommends http://www.sepscience.com/Techniques/GC ... rimination. Recommend a tapered liner.

Is a tapered liner lined with glass wool a good choice for FAME assay?

How often do you change your inlet liner? I understand the change frequency could be affected by the particular samples, but I don't have any idea how often they need to be changed. Weekly? Monthly? Or roughly how many injections?

[Consumer Products Guy]

I do FAME assays regularly on both packed (yes, packed) and on capillary columns. I like the cyanopropylsilicone columns better than PEG, my opinion.

Anyway, I'd suggest FocusLiner or the straight-through liner with the deactivated glass wool in the middle for split injections.

[tiggeria]

Thank you for your input, Consumer Products Guy!

Will you suggest taper near the bottom on the FocusLiner? My limited reading gave me an impression that I've got to pick up a liner with a taper down close the column end, to reduce high boiling point component discrimination.

How often do you change your liner?

On the column coating, I don't have a choice now since that is the column I have on hand. I do notice that PEG is the worst material to sustain oxygen degradation. Other than that, I do not know much about it . In what aspects cyanopropylsilicone columns are better?

I would use packed column, then I do not need to care as much about the gas quality, and am not afraid to destroy the packed column by dirty samples, since it would be cheaper to replace. However, I was told that I should not use it because the resolution is not good enough for biological samples, such as red blood cells, plasma, and milk etc.