Chromatography Forum

Hi all,

in analyzing food sample, first homogenize sample , dope surrogates, then extract and finally clean-up. After cleaning up, we spike analytes into the final extract (for blank sample) and analyze by GC/MS or LC/MS/MS to create matrix-matched calibration (eg. 3 levels)
I have a question: why don't we spike analyte just before the extraction step to make calibration curve. I think that also covers the recovery and we do not need surrogates ?

It isn't quite the same.
The procedure of spiking an extract tells you instrument response in the matrix. Spiking prior to extraction gives a procedural standard calibration which adjusts for losses during extraction. You won't actually know what the losses are.
Both are used in different contexts.