Db 1301 column

1,1,2,2-tetrachloroethene (≥99.5%), 1,1,2-trichloroethene (99.5%), trans-1,2-dichloroethene (trans-1,2-DCE; ≥98%), 1,1-dichloroethene (1,1-DCE; ≥99%), cis-1,2-dichloroethene (cis-1,2-DCE; ≥97%), 1,2-dichloroethane (1,2-DCA; ≥99%) and vinyl chloride (VC; 100 μg/mL in methanol) were purchased from Sigma-Aldrich (St. Louis, MO, United States). All other chemicals used to prepare analytical standards or feed solutions were analytical reagent grade.
Two milliliters of liquid samples obtained from the cathode chambers were immediately transferred to sealed 10 mL bottles filled with the high purity N₂ gas (≥99.99%). The bottles were placed in a 25°C shaker for 30 min to reach the equilibrium. Concentrations of volatile organic compounds including PCE, TCE, trans-1,2-DCE, 1,1-DCE, cis-1,2-DCE, 1,2-DCA, and VC in the headspace (8 mL) were determined using a gas chromatograph (Agilent 7890A, Palo Alto, CA, United States) equipped with a 63Ni electron capture detector and DB-1301 column (30 m × 250 μm × 0.25 μm, Agilent). Ethene and methane were determined using a gas chromatograph (Agilent 7890A, Palo Alto, CA, United States) equipped with flame ionization detector (FID) and HP-5 column (30 m × 250 μm × 0.25 μm, Agilent). Headspace concentrations were converted to aqueous-phase using tabulated Henry’s law constants (Chen et al., 2018 (link)).

Concentrations of higher alcohols (isobutyl, isoamyl and amyl alcohol, 1-propanol), esters (ethyl acetate, ethyl lactate), methanol, and acetaldehyde were determined using a head space solid phase microextraction (HS-SPME), followed by gas chromatography. First, 10 mL of the juice sample was mixed with 1 mL of 2-pentanol as an internal standard (20 mg/L). Then, to extract the volatile compounds, a poly dimethylsiloxane/Divinylbenzene (PDMS/DVB) fiber (Supelco, PA, USA) was used. A 1.7 mL sample was placed into a 5 mL headspace vial and 0.49 g of sodium chloride was added. After 5 min of equilibration at 25°C and agitation of 1,200 rpm, the fiber was inserted into the headspace and the solution was swirled in a magnetic stirrer at 12,000 rpm and 60°C for 30 min. The fiber was then transferred to the injector for desorption at 270°C for 15 min. Gas chromatography analysis was performed on a Shimadzu Plus 2010 GC system equipped with a flame ionization detector, using a DB-1301 column (60 m, 0.250 mm, film thickness, 1 μm, Agilent). The oven temperature was programmed at 40°C for 16 min, followed by a gradual increase of temperature at a rate of 5°C/min up to 60°C, and then raised to 260°C at a rate of 70°C/min. The gas carrier was hydrogen at a flow rate of 2.0 mL/min.