I Want to estimate the FAME % in transesterified oil sample using either GC OR HPLC so please suggest me the name of standard that I can use as a reference.
For GC - if you're using an internal standard, hexadecane is commonly used as it doesn't overlap with the major peaks and has a similar molecular mass and effective carbon number to the main FAME molecules in the oil.
For HPLC and GC external standards, I use methyl palmitate or methyl stearate as they are stable and have a very long shelf life, meaning you can use the same initial standard as a reference point for a long time.
Thank you Tom for your valuable response. Could you please explain how I can calculate the % of FAME from peaks of GC AND HPLC.
Then you'll need to either run GC-MS/HPLC-MS first to identify, or run standards of your FAME components to identify by retention time. At minimum this would be Methyl Palmitate, Stearate, Oleate and Linoleate. You may want to add Methyl Linolenate as well. Do you have any literature on your oil to suggest what other fatty acids may be present?
Retention Time
10.509
12.275
14.585
15.044
15.741
16.529
17.654
21.179
24.231
These are the retention time of the sample after GC analysis.
Without knowing your column or conditions or seeing your chromatogram, I can't confirm which is which. However the saturated FAME compounds are generally separated ~2 seconds apart. Monounsaturated come slightly before them, diunsaturates slightly before that, etc etc. So from that pattern, and assuming that the 14 - 16 second peaks are your largest, I would guess you have, in this order:
Methyl laurate (12:0), methyl myristate (14:0), methyl palmitate (16:0), methyl linoleate (18:2), methyl oleate (18:1), methyl stearate (18:0), methyl arachidate (20:0), methyl behenate (22:0)
This is the chromatograph so please help me to find out the compounds and their percentage.
You've got the compounds, you just need to convert the peak areas to concentration based on your calibration. I'd also recommend running again with a slower ramp rate - resolution isn't great for accurate calculations.
The standard test method for FAME content is EN 14103. It is a GC test with internal standard. One can use many different methods, either can give a reliable result, but the standard is the one listed in EN 14214
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EN14103 is the official method for ester content in biodiesel, the HPLC tests are indicative, but not standardized, yet
a lot of researchers are using GC for the estimation you ve required,however it's a fair idea to prepare a sample which you know it's composition and test it by GC or HPLC to see weather the test gives accurate results or not.
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