Poraplot q column

A portion of the studied rock sample was initially crushed with a stainless steel mortar and pestle and sieved to collect 1–2 mm chips. These chips were then heated at 60 °C under vacuum to remove surficial water. Approximately 0.23 g of these chips were placed into a hydraulic rock crusher with a continuous He stream similar to that of Potter and Longstaffe (2007)^{94 (link)} and the crusher activated several times until the CH₄ signal approached that of the blank. The gas released by crushing was focused on a Porapak Q filled quartz capillary trap held at liquid nitrogen temperature. Gases were released from the trap by moving it out of the liquid nitrogen and into a 150 °C heating block.
The released gases were separated on a HP 6890 gas chromatograph fitted with an Agilent Poraplot Q column (50 m, 0.32 mm wide bore, 10 μm film) temperature programmed from −30 to 80 °C. The column effluent was fed into an oxidation oven containing NiO, CuO and Pt catalysts where the reduced gases were converted to CO₂. Following the oxidation oven, the gases entered a Thermo Fischer Delta V isotope ratio mass spectrometer (IRMS). Data reduction was performed by comparing an in house CH₄ isotope standard to Indiana University Biogeochemical Laboratory CH₄ standards #1, #2, #5, and #7.

The activity of pMMO was tested by assaying the conversion of propene to propylene oxide^{55 (link)} using gas chromatography-mass spectrometry (GC–MS),comprising of a 7890A GC system coupled to a 5975C VL MS detector (Agilent Technologies) and fitted with a Poraplot Q column (25 m × 0.25 mm, Agilent Technologies). The Injection temperature and MS temperature were 250 °C. The column temperature was held at 180 °C for 8 min, then ramped up to 250 °C at 50 °C min⁻¹ and held for 5 min. The flow rate of carrier gas (nitrogen) was 1 ml min⁻¹, and the split ratio was 50:1. Detection was carried out using selected ion monitoring at 58.1 m/z corresponding to propylene oxide.

Samples for gas chromatography measurements were taken from the shake flask headspace during the gas flow phase of the RAMOS measurement cycle. Gas sampling bags (0.3 L, PVDF, Chemware, Raleigh, North Carolina, USA) were attached to the gas outlet of a shake flask and flushed with gas from the flask headspace for 5 min to allow for saturation of the bag material with ET. Next, the gas bags were emptied by pulling vacuum with a syringe and then refilled for 10 min. The sample volume taken from the shake flask was approximately 110 mL. The gas chromatograph (GC) was a Thermo Fisher Trace GC Ultra (Thermo Scientific, Schwerte, Germany) using a PoraPlotQ column (30 m × 0.32 mm ID, Agilent Technologies, Santa Clara, California) and helium as carrier gas. As detector a Thermo Fisher ISQ mass spectrometer (MS) was used (Thermo Scientific, Schwerte, Germany). Calibration gas containing 1 ppm ET in air and a gas mixture (using aforementioned calibration gas) containing 0.1 ppm ET in air served as standards for GC-MS measurements. Every sample taken from a shake flask was analyzed three times.