[Golden_4_Life]

I had been under the assumption that when two different chemical methods--each relying on a different independent chemical principle--are used to analyze a common sample, then the result of the analysis ought be nearly identical.
For example, if the concentration of a certain drug metabolie is measured in urine via GC/MS to be 100 ng/uL; then when that same sample is analyzed by HPLC it SHOULD be found to be 100 ng/uL.  Using the same calibration stds etc... Isn't this correct thinking?  Pls address any misconceptions that I may be operating under. Looking fwd to your posts.

[JGK]

If the methods have been correctly developed and validated the should give similar results.

I would hesitate to use the word "identical" as the procedures used in each analysis will be subject to variations. although method validation attempts to minimise variation it will never eliminate it.

[Golden_4_Life]

OK, so then I am operating under the correct mind-set in my analytical world. Thanky JGK