Hi, I ran analysis on the concentration of Fatty Acids Methyl Ester (FAME) of freeze-dried fish sample using Shimadzu GC2010Plus and its companion software GC Solution.
I first plotted a 4 points calibration curves using the 37 FAME mix. Then I used the same method to run all my samples. I diluted my FAME sample 5 times so that all detected fatty acids had concentration within the standard curve. Finally, the software reported my after post-processing in parts per million (ppm).
Naturally, I multiplied the results reported with a factor of 5 to obtain the concentration before dilution, but here are my questions:
Q1: Are those auto-generated concentration I obtained after multiplying with 5 is what I should report directly in my writing, as in the unit of ppm?
Q2: Or should I further express the data from Q1 according to the freeze-dried sample weight (mg) I used for each sample? So I can accurately reflect the actual FAME concentration in per gram of freeze-dried/wet fish samples. If yes, how? If no, why?
Note:
- I am aware of the presence of calculating the sample concentration based on the ratio between Internal Standard and Sample's peak areas. However, my internal standard C19:0 co-eluted with my FAME-Mix C18:3n6.
- The quantitation method I selected in the software is based on "External Standard" method by comparing the retention time and peak area from my calibration curves. I wonder if what the software reported is the same as to manual calculation based on peak areas ration and such...
- To see my sample extraction method, here: Article One-step method for quantitative and qualitative analysis of...
Any helps are much appreciated.
Hello Chee ping Tan,
You will get concentration of Fatty acid methyl esters from calibration curve of respective standard FAME. Suppose, standard concentration levels are in ppm then you will get FAME concentration of sample in ppm from regression equation of standard calibration curve. Suppose that 20 mL was the final volume of sample after extraction of 2 g dry substance. Further, suppose you get 5 ppm palmitate in the sample by GC FID and Lab solution software. So, what is the concentration of palmitate in dry substance? 5 ppm. Not! Clear that 5 ppm = 5 ug/mL and the final volume of sample was 20 mL. Now, concentration of palmitate per 2 g dry substance = Final volume of sample (20 mL) x Concentration (5 ug/mL), = 100 ug/2 g = 50 ug/g = 0.05 mg/g. Like this, you can calculate the amount of FAME per gram or further can be converted to percentage. I think from this you will solve your queries. Good luck! For further queries contact me on my email id: [email protected].
Nitin S. Kadam , thank you for the reply. Very helpful indeed! I appreciate it very much.
I you are not sure of the results from the software.
Make a calibr. curve in Excel and use areas for manual calculations.
regards,
GB
Dear Boczkaj,
I suppose that would work. Thanks for the input.
Thank you.
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