Problems in analysing stearic / oleic acid [June 16, 2004]
Posted: Tue Aug 24, 2004 9:37 pm
By soh on Wednesday, June 16, 2004 - 02:33 am:
I'm working on the quantification of sugar fatty acid esters using Waters Symmetry C18 column (4.6 x 150 mm, 5 um & its guard column). Oleic acid as one of the reactants and stearic acid is in used as an internal standard. Mobile phase is acetonitrile : acetone in 80 : 20 in gradient mode. The resolution and intensity of the two peaks related to stearic acid and oleic acid is pretty good when the column is still new. After a few runs, the problems of peak shifting, broadening, tailing and decreasing in intensity start. Flushing the column using acetone seems like doesn't help. However, the peaks regarding to sorbitan esters are still nice in term of separation and intensity (peak shape as well). Regeneration of column had been performed. Yet, it failed to give a good results. Does anyone of you experienced this phenomenon before? Any solution met? Thanks...
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By Consumer Products Guy on Wednesday, June 16, 2004 - 08:03 am:
We always use GC for fatty acid esters, can separate stearic and oleic easily on most columns. On non-polar columns oleic elutes first, and on polar columns like OV-225, Rtx-2330, PEG stearic elutes first.
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By soh on Thursday, June 17, 2004 - 10:29 pm:
To: Consumer Products Guy
Thanks for your advice. But i have a question. Is GC suitable for analyzing sorbitan fatty acid esters?
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By Anonymous on Friday, June 18, 2004 - 06:00 am:
Intact sorbitan fatty acid esters are too non-volatile for GC, I believe, just from the top of my head.
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By soh on Tuesday, June 22, 2004 - 11:44 pm:
We just changed the guard column. It works! It gave a better resolution. However, the peak was shifted to higher retention time if compared to the previous results. It seems like the life span of the guard column is shorter than we are expected. Anyway, thanks so much for your advise.
I'm working on the quantification of sugar fatty acid esters using Waters Symmetry C18 column (4.6 x 150 mm, 5 um & its guard column). Oleic acid as one of the reactants and stearic acid is in used as an internal standard. Mobile phase is acetonitrile : acetone in 80 : 20 in gradient mode. The resolution and intensity of the two peaks related to stearic acid and oleic acid is pretty good when the column is still new. After a few runs, the problems of peak shifting, broadening, tailing and decreasing in intensity start. Flushing the column using acetone seems like doesn't help. However, the peaks regarding to sorbitan esters are still nice in term of separation and intensity (peak shape as well). Regeneration of column had been performed. Yet, it failed to give a good results. Does anyone of you experienced this phenomenon before? Any solution met? Thanks...
-------------------------------------------------------------------------------------------------------
By Consumer Products Guy on Wednesday, June 16, 2004 - 08:03 am:
We always use GC for fatty acid esters, can separate stearic and oleic easily on most columns. On non-polar columns oleic elutes first, and on polar columns like OV-225, Rtx-2330, PEG stearic elutes first.
-------------------------------------------------------------------------------------------------------
By soh on Thursday, June 17, 2004 - 10:29 pm:
To: Consumer Products Guy
Thanks for your advice. But i have a question. Is GC suitable for analyzing sorbitan fatty acid esters?
-------------------------------------------------------------------------------------------------------
By Anonymous on Friday, June 18, 2004 - 06:00 am:
Intact sorbitan fatty acid esters are too non-volatile for GC, I believe, just from the top of my head.
-------------------------------------------------------------------------------------------------------
By soh on Tuesday, June 22, 2004 - 11:44 pm:
We just changed the guard column. It works! It gave a better resolution. However, the peak was shifted to higher retention time if compared to the previous results. It seems like the life span of the guard column is shorter than we are expected. Anyway, thanks so much for your advise.