Pal autosampling system

UTAK drug-free normal urine, Parafilm, pH paper, and polypropylene cups for urine collection were purchased from ThermoFisher Scientific (Waltham, MA, USA). Sodium hydroxide (50% wt. in solution, nitrogen flushed extra pure) and sodium chloride (99.85% pure) were also purchased from ThermoFisher Scientific. Guanidine hydrochloride (GHCl; pH = 8.5) was purchased from Sigma Aldrich (St. Louis, MO, USA). SPME fibers coated with DVB/CAR/PDMS (two centimeters in length) were purchased from Supelco (Bellefonte, PA, USA). SPME arrows of a similar chemical composition (DVB/Carbon Wide Range/PDMS) were obtained from Restek (Bellefonte, PA, USA). Headspace vials (10 mL) with screw-on caps were purchased from Restek or Agilent (Santa Clara, CA, USA). An Agilent 7890A GC system coupled to an Agilent 7200 MS quadrupole time-of-flight (QTOF) equipped with a PAL autosampling system (CTC Analytics, Zwingen, Switzerland) was used to incubate, extract, and analyze the VOCs. The GC column utilized for VOC separation was a Restek Rxi-5ms column of 30 m in length, a 0.25 mm internal diameter, and a 0.25 μm film thickness.

A two-centimeter divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/ PDMS) SPME fiber (purchased from Sigma Aldrich, St. Louis, MO, USA) was used to preconcentrate VOCs. Guanidine hydrochloride (GHCl; pH = 8.5) was purchased from Sigma Aldrich and used to denature major urinary proteins (MUPs), as they bind VOCs in hydrophobic pockets [35 (link)]. Headspace vials with a volume of 10 mL were purchased from Thermo Fisher Scientific (Waltham, MA, USA) and were used for urine sample storage and analysis. An Agilent (Santa Clara, CA, USA) 7890A GC system coupled to an Agilent 7200 MS quadrupole time-of-flight (QTOF) equipped with a PAL autosampling system (CTC Analytics, Zwingen, Switzerland) was used to incubate, extract, and analyze VOCs. The GC column utilized for VOC separation was an Agilent Ultra Inert HP-5 ms with 30 m length, 250 μm internal diameter, and 0.25 μm film thickness. MATLAB R2020a and Origin were used to generate figures.