Rxi 17

Pegasus GCxGC-TOFMS (Leco Corporation Joseph, MI, USA) that uses an Agilent 7890A GC (Atlanta, GA) coupled to a time-of-flight mass spectrometer (TOFMS) (Leco Corporation, St Joseph, MI, USA) equipped with a Gerstel Multipurpose sampler, was used for chromatographic analyses of the derivatized samples. One µL of serum extract was randomly injected at a split ratio of 1:50 and the carrier gas used was helium at a flow rate of 1 ml min⁻¹. For the entire run, the temperature of the injectors was kept constant at 270°C. A Restek Rxi-5Sil MS capillary column (29.145 m × 0.25 μm d.f.) was used as the primary column. The primary oven was programmed to an initial temperature of 70°C for 2 min to obtain a compound separation. Subsequently, this was followed by a 4°C per minute increase to a final temperature of 300°C where it was maintained for 2 min. The second separation of compounds was achieved using a Restek Rxi-17 (1.400 m, 0.25 µm i.d., 0.25 μm d.f.) column. The secondary column used was set to the same temperature parameters as that of the primary column. The filament bias was EI at 70 eV while the detector voltage was at 1,600 V. Subsequently, the mass spectra were collected at an acquisition rate of 200 spectra per second with a source temperature of 220°C and a solvent delay of 400 s from 50 to 800 m/z (Du Preez and Loots 2013 (link)).