Plasma samples (0.2 mL) were extracted using a Waters Oasis MAX (10 mg) 96-well plate and the resulting samples were analyzed using an Applied Biosystems API-5000 HPLC-MS/MS with an electrospray ionization (ESI) source.
Between the otherwise Amtrak-proscribed legs of a trip west, Charmaine and I had a few days to make the drive from the definitively hot low-desert town of Tucson to the cooler, higher (but likewise artificially watered) oasis of Albuquerque.
One has an infinity-edge and a swim-up bar; the other occupies a natural rock cavern brilliantly transformed into a splashy salt-water oasis that includes a hot tub (picture a hipster Barney Rubble on vacay).
SPE analysis was performed on Oasis cartridges (Waters Oasis® HLB, 30 μm, 60 mg) that were preconditioned with 1 ml ethanol followed by 5 ml water.
A pre-column (Waters Oasis HLB, 25 μm, 20 × 3.9 mm) and a reversed phase HPLC column (Phenomenex Bondclone C18, 10 μm, 250 × 4.6 mm or Phenomenex Synergi Max-RP 80A C18, 4 μm, 250 × 4.6 mm) in series, with a switching valve between columns was utilised.
The fractions were desalted, eluted, and dried as described above using Waters Oasis HLB column.
The filtrate (plasma peptidome) containing the low MW naturally occurring peptides was processed with Waters Oasis HLB Extraction Cartridges (Waters Corporation, Milford, MA), and extracted with ethyl acetate.
The filtrate (urine peptidome) containing the low MW naturally occurring peptides was processed with Waters Oasis HLB Extraction Cartridges (Waters Corporation, Milford, MA) and extracted with ethyl acetate.
The supernatant was then removed and the sample was concentrated on a C8 HLB Cartridge (Waters Oasis) into 1 mL of MeOH.
For tryptophan, kynurenine and their metabolites the analytes were extracted from samples and calibrators/controls using Waters Oasis MCX 1 cc (30 mg) extraction cartridges.
