[jbays1973]

Hello.  I am involved in a project working towards identifying lipid residues in soil samples.  One of the scientists advising me has suggested that I "spike" my control soil samples with a set of free fatty acids.  These would be selected such that they represent fatty acids commonly found in this type of soil.  I am tyring to reason this suggestion out.  This is what I have come up with.

By spiking with the free fatty acids I would be able to easily identify the methyl ester derived after extraction, (I intend to extract and transesterify the freed fatty acids and then "spike" with the representative set).  I think that the fatty acid will elute slightly before the derived methyl ester.  I also think that "spiking" with known concentrations allows for easy quantitation of the fatty acids that were in the control.  

So, do I just use the reference set to generate a standard to use for calibration when I run the sample set of unknowns?

Any feedback would be sincerely appreciated.

Jim  

[kevins]

The objective of "spike" are as follow:
1. To confirm the result. e.g. the first trial is X mg/L in the sample then you add y mg/L to same sample and read again, the reading should be X+y mg/L. This method can also be used to the very low concentration of substance.
2. To calculate the extraction efficiency. Because of the efficiency is unknown.