High-throughput liquid chromatography differential mobility spectrometry mass spectrometry for bioanalysis: determination of reduced and oxidized form of glutathione in human blood

Currently, the measure of the oxidative stress, from oxidized and reduced glutathione (GSSG and GSH respectively), for large cohorts of samples, is generally limited to spectrometric methods. In this study, a high-throughput assay for GSH after derivatization with N-ethylmaleimide and GSSG in blood sample was developed with an analysis time of 1.5 min. The method combines protein precipitation and a short LC (10-mm length) column where compounds were trapped in front-flush mode and eluted in back-flush mode. This setup is combined with modifier-assisted differential ion mobility spectrometry (DMS, SelexIon) and detection is performed in the selected reaction monitoring mode using positive electrospray ionization. In DMS, various modifiers were investigated including N-2, methanol, toluene, ethanol, acetonitrile, and isopropanol to improve assay selectivity. Using EtOH as modifier, the limit of quantification (LOQ) was found to be 0.4 mu M for GSSG and 3.2 mu M for GS-N-ethylmaleimide (NEM) using a blood volume of 60 mu L. The method is linear over a wide dynamic concentration range of 0.4 to 400 mu M for GSSG and from 3.2 to 3200 mu M for GS-NEM. The inter-assay precision of QC samples were <= 6.7%, with accuracy values between 98.3 and 103%. The method was further cross-validated with a LC Hypercarb-DMS-MS/MS method by the analysis of human blood samples. The bias between both assays ranged from -0.3 to 0.2%.