Liquid chromatography, in combination with a quadrupole time-of-flight instrument, with sequential window acquisition of all theoretical fragment-ion spectra acquisition: validated quantification of 39 antidepressants in whole blood as part of a simultaneous screening and quantification procedure.

Sequential window acquisition of all theoretical fragment ion spectra (SWATH) is a data independent acquisition (DIA) method for very fast scanning quadrupole time-of-flight (QTOF) instruments. SWATH repeatedly cycles through 28 consecutive 20 Da precursor isolation windows detecting all precursor ions and fragments MS ALL like and yet fast enough to generate more than 10 data points over the chromatographic peak. It was already shown in previous publications that SWATH, despite its wide Q1 windows, allows the identification of different substances and that SWATH has a higher identification rate than data dependent acquisition approaches. The aim of this study was a proof of concept study whether these same data sets can also enable validated quantification according to international guidelines, exemplified for 39 antidepressants. The validation included recovery, matrix effects, process efficiency, ion suppression, and enhancement of coeluting ions, selectivity, accuracy, precision, and stability. The method using SWATH acquisition proved to be selective, sensitive, accurate, and precise enough for 33 out of the 39 antidepressants. The applicability of SWATH for screening and validated quantification in the same run was successfully tested with authentic whole blood samples containing different antidepressants and other drugs thus proving the QUAL/QUAN abilities of SWATH. In an additional systematic investigation, it could be shown that calibration curves injected a few days after or before the actual sample can be used for quantification with acceptable accuracy.