Qp2010 ultra

Prior to derivatization, 100 μL of a methanolic solution of betulinic acid (0.5 mg/mL) was added as an internal standard to 100 μL of the OA-containing sample. The mixture was evaporated to dryness under a N₂ stream, and the residue dissolved in 200 μL of the silylating reagent (BSTFA + 1% TMCS in pyridine).
OA was identified and quantified using a coupled GC–mass spectrometry detector (GC-MS) QP2010 Ultra (Shimadzu Europa GmbH, Duisburg, Germany) with an AOC-20i autosampler, an ion source of electron impact and a quadrupole detector. The analysis was carried out in splitless mode, with an injector temperature of 290 °C. Helium was used as a carrier gas at 53.1 kPa and of 1mL/min. The oven temperature program was as follows: initial temperature, 50 °C/1min; 50–200 °C at 40 °C/min; 200–280 °C at 10 °C/min; and finally held for 2 min. Total run time was 14.75 min. The MS conditions were: interface temperature, 280 °C; ion source temperature, 220 °C; electron impact, 70 eV; acquisition mode, scan (m/z 50–600). OA was identified by comparing the retention times and abundance ratios of two fragments ions (203 and 189 m/z).

Extracts were prepared using 10 mg of each sample and 500 µL of dichloromethane (CH₂Cl₂), followed by vortex agitation (5 min, room temperature) and ultrasonic bath (15 min, room temperature). The extracts were filtered through cotton wool using a glass syringe. After solvent evaporation, each sample was solubilized with CH₂Cl₂ in a concentration of 10 mg·mL⁻¹.
GC-MS analyses were performed in a gas chromatograph coupled to a quadrupole mass spectrometer (QP2010 Ultra, Shimadzu Corporation, Kyoto, Japan) using a ZB-5MS column (30 m × 0.25 mm × 0.25 µm) and a temperature program of 60–300 °C at 5 °C·min⁻¹ (60 °C, 3 min; 60–300 °C, 51 min and 300 °C, 71 min). The following conditions were employed: carrier gas, He; column oven temperature, 60 °C; injection temperature, 270 °C; injection mode, split; injection volume, 1.0 µL; flow control mode, linear velocity; pressure, 86.7 kPa; total flow, 11.4 mL min⁻¹; column flow, 1.40 mL min⁻¹; linear velocity, 43.2 cm s⁻¹; purge flow, 3.0 mL·min⁻¹ and split ratio, 5. The mass spectra were acquired in the scan mode between 35 and 500 m/z, with an ion source temperature of 250 °C and EI voltage of 70 eV. Chromatograms and mass spectra were visualized using the GC Solutions (version 4.20 for Windows, Shimadzu Corporation, Kyoto, Japan).

For GC analysis of 25 mg.L⁻¹ 2-CP, degraded with 1 g.L⁻¹ GCF1 under visible light, 5 mL aliquots were taken at specified intervals, filtered through 0.22 μm membrane filters and analyzed for the residual 2-CP concentration using GC. To determine the intermediate products, each test sample (0, 30, 90, 150 min) was extracted thrice using 25 mL of Dichloromethane (DCM). Extract thus obtained was dried using anhydrous Na₂SO₄. Samples were subjected to the GC (QP2010 ultra, Shimadzu) having a DB-5ms capillary column using He as carrier. Initial column temperature for 3 min was maintained at 50 °C followed by a gradual temperature increase at 5 °C min⁻¹ up to 250 °C. Injector and detector temperatures were fixed at 200 and 260 °C, respectively.