title: Stepwise optimization approach for improving LC-MS/MS analysis of zwitterionic antiepileptic drugs with implementation of experimental design.
abstract: In this article, a step-by-step optimization procedure for improving analyte response with implementation of experimental design is described. Zwitterionic antiepileptics, namely vigabatrin, pregabalin and gabapentin, were chosen as model compounds to undergo chloroformate-mediated derivatization followed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis. Application of a planned stepwise optimization procedure allowed responses of analytes, expressed as areas and signal-to-noise ratios, to be improved, enabling achievement of lower limit of detection values. Results from the current study demonstrate that optimization of parameters such as scan time, geometry of ion source, sheath and auxiliary gas pressure, capillary temperature, collision pressure and mobile phase composition can have a positive impact on sensitivity of LC-MS/MS methods. Optimization of LC and MS parameters led to a total increment of 53.9%, 83.3% and 95.7% in areas of derivatized vigabatrin, pregabalin and gabapentin, respectively, while for signal-to-noise values, an improvement of 140.0%, 93.6% and 124.0% was achieved, compared to autotune settings. After defining the final optimal conditions, a time-segmented method was validated for the determination of mentioned drugs in plasma. The method proved to be accurate and precise with excellent linearity for the tested concentration range (40.0 ng ml(-1)-10.0 × 10(3)  ng ml(-1)).
authors.affiliation: University of Belgrade, Faculty of Pharmacy, Department of Drug Analysis, Vojvode Stepe 450, Belgrade, Serbia.
authors.forename: Nađa
authors.initials: N
authors.lastname: Kostić
authors.forename: Yannis
authors.initials: Y
authors.lastname: Dotsikas
authors.forename: Anđelija
authors.initials: A
authors.lastname: Malenović
authors.forename: Biljana
authors.initials: B
authors.lastname: Jančić Stojanović
authors.forename: Tijana
authors.initials: T
authors.lastname: Rakić
authors.forename: Darko
authors.initials: D
authors.lastname: Ivanović
authors.forename: Mirjana
authors.initials: M
authors.lastname: Medenica
mesh_terms: D000927:Anticonvulsants / Q000032:analysis* / Q000097:blood / Q000737:chemistry; D002853:Chromatography, Liquid / Q000379:methods*; D006801:Humans; D057230:Limit of Detection; D015203:Reproducibility of Results; D012107:Research Design; D053719:Tandem Mass Spectrometry / Q000379:methods*; D005680:gamma-Aminobutyric Acid / Q000032:analysis* / Q000097:blood / Q000737:chemistry
chemical_list: D000927:Anticonvulsants; D005680:gamma-Aminobutyric Acid
keywords: antiepileptics; experimental design; ion source parameters; optimization; response surface methodology