Sample extraction was initially evaluated with the protein
precipitation and LLE technique, but the sample extraction recovery
was very low. The use of SPE extraction was found to better in
sample cleanup, with a better sample extraction recovery. The
optimization of elution solution was critical phase in the SPE
extraction optimization and the use of mixture of 5 mM ammonium
acetate(pH~3.5), acetonitrile and methanol as elution solvent has
ensured sample extraction from matrix of about 99% for all
analytes. The time consuming and error-prone solvent evaporation
and reconstitution steps were avoided and a direct elution
procedure has shown a clean sample with low sample extraction
process duration ready for analysis. The optimized detection,
sample extraction chromatography enabled to reduce processing
and analysis time without compromising the sensitivity.