Firstly I know that LC or HPLC may well be more suited for this analysis.
I am having real problems in developing a Diclofenac method using GC/MS.
I am using a d4 version of Diclofenac as an internal standard. PFPA, followed by a tBDMSi derivitisation process.
I am calibrating in a range from 0.5-50ng/ml.
I have been having some very peculiar results, with 5-25ng/ml being linear. At <5ng/ml, responses leap, throwing the whole calibration curve off.
I can supply more details, such as GC temp. program, injection volume, etc. The matrix is human fluid (serum/plasma).
Reprouducibilty is also a problem.