Chromatography Forum

hello,all; have problem with stearic acid value in sunflower oil.; injected the sample,but the value is below the its actual value ..the result is 1,30 ( actual value is 2,7-3,5).also,other acid values are normal..; changed oven program,clean septum,injector...what can be the problem...

thank you.....please read it...

I assume that your making fatty acid methyl esters, then doing GC. First of all, why do you think that your values are "wrong" and that the supplied or literature values are correct? Small differences in biological samples can be due to climate differences, strain differences, etc. How does your chromatography look, especially the separation between the stearic and the unsaturated C-18 peaks? Obtain a standard mix of unsaturated FAMEs, and see how that looks.

I meant saturated FAMEs, still can't type.

I assume that your making fatty acid methyl esters, then doing GC. First of all, why do you think that your values are "wrong" and that the supplied or literature values are correct? Small differences in biological samples can be due to climate differences, strain differences, etc. How does your chromatography look, especially the separation between the stearic and the unsaturated C-18 peaks? Obtain a standard mix of saturated FAMEs, and see how that looks.

The method you said that is true.But i injected the same oil esters bfore the gc is this situation.Also the soybean and other oils esters gc the stearic acid value is lower than its actual value...such is the literatur is 2,80,result is 0,80....also ; checked myself the old oil samples so i think it should be the same....and stearic acid is seperated well the other acids because ; done good oven programme.but once again ; will make fame mixture...
can column be problem,a part of its especially.
60*0,25 bpx 70 sge column...perkin elmer autosytem xl gc...