Rapid and Robust Analysis Method for Quantifying Antidepressants and Major Metabolites in Human Serum by UHPLC-MS/MS

Results of several hundreds of serum samples were compared. There is a good correlation between the results from HPLC-DAD and UHPLC-MS/MS. Correlation coefficient is between 0.950 and 0.998 for all compounds.
The overall run time was 6.5 minutes, reducing analysis time by more than a factor of 2. With an identical Kinetex XB-C18 column of 75mm length the run time can be further shortened to less than 5 minutes.
The serum extracts obtained after off-line solid phase extraction are very clean. No ion suppression or ion enhancement was observed. There is no need for isotopically labeled internal standards.
Reconstitution of the sample extract by solvent evaporation and subsequent dilution in another solvent is mandatory for HPLC-DAD to increase concentration and to eliminate peak broadening of early eluting compounds, but not necessary for UHPLC-MS/MS. Therefore sample pretreatment could be shortened, reducing the overall sample prep time from 40 to 15 minutes per batch of 15 samples.
UHPLC-MS/MS generates less false positive results than HPLC-DAD due to its inherent selectivity. In routine HPLC-DAD analysis it is very common to change the quantitation wavelength when co-elution with another known drug is observed.