Hp plot q capillary column

Eight fruit were sealed inside a 4.2-L plastic container for 2 h at 25°C. Aliquots (1 mL) of headspace gas were withdrawn from each container and injected into a gas chromatograph (GC-9A; Shimadzu, Kyoto, Japan). Carbon dioxide (CO₂) concentrations were determined using a thermal conductivity detector and a Poropak N column (Shimadzu). Ethylene concentrations were measured using a flame ionization detector and an HP-PLOT Q capillary column (Agilent Technologies, Palo Alto, CA, USA). Rates of ethylene production and respiration were expressed on a fresh weight basis.
Fruit color was measured with a Konica Minolta CR-400 colorimeter (Konica Minolta Co. Ltd., Tokyo, Japan) in the CIE-L^*a^*b mode. Color changes were quantified as the hue angle with the formula h = 180° + tan⁻¹ (b^*/a^*) in accordance with Li et al. (2012 (link)). The contents of chlorophyll and carotenoids were determined spectrophotometrically following the method of Lichtenthaler (1987 (link)).
Membrane permeability was expressed as relative electrolyte leakage and measured in accordance with the method of Sun et al. (2012 (link)). Malondialdehyde (MDA) content was measured following the method described by Huang et al. (2013 (link)).

Each catalyst was pelletized without a binder, roughly crushed, and then sieved to obtain 500–600 μm particles. These catalyst particles (typically 100 mg) were placed in a fixed-bed reactor (a down-flow quartz tube microreactor with a 9 mm internal diameter) situated in an electric furnace. Each sample was first pretreated at 550 °C for 1 h under an air flow at 40 cm³(NTP) min⁻¹ and then maintained at 400 °C under a He flow at 40 cm³(NTP) min⁻¹, acting as a carrier gas. While maintaining the specimen at 400 °C, DME (at a partial pressure of 5.0 kPa) was introduced through the top of the reactor. The contact time, W/F (where W value is catalysts weight and F value is flow rate of DME), was 20 g-cat h mol⁻¹ in these trials but could be varied by changing the flow rate or catalyst amount if necessary. The reactants and products were analyzed by gas chromatography (GC 2014, Shimadzu) using a DB-5 capillary column (Agilent Technologies Inc., Santa Clara, CA, USA; id 0.53 mm, length 30 m, 5.00 μm thick stationary phrase) and an HP-PLOT/Q capillary column (Agilent Technologies; id 0.53 mm, length 30 m, 40.0 μm thick stationary phase) together with a flame ionization detector.

CB concentration was analyzed by a GC (6890N, Agilent Technologies, Palo Alto, CA, USA) coupled with a flame ionization detector and a HP-Innowax capillary column (30 m × 0.32 mm × 0.5 μm). The temperatures of the injector, column and detector were maintained at 200 °C, 100 °C and 180 °C, respectively. The carrier gas was N₂, at a flow rate of 33.4 mL/min.
CO₂ concentration was measured on a GC (6890N, Agilent Technologies) equipped with a thermal conductivity detector and an HP-Plot-Q capillary column (30 m × 0.32 mm × 20 μm). The temperatures of the injector, column and detector were 90 °C, 40 °C, and 180 °C, respectively. Helium was used as a carrier gas at a rate of 5 mL/min.
Cell concentration was determined by optical density using a spectrophotometer (U-2910, Hitachi High Technologies, Tokyo, Japan) at 600 nm. A calibration curve between cell concentration and optical density was constructed prior to this analysis (y = 222.93x − 0.69, where y = mg/L cell concentration and x = OD₆₀₀).

A. vinelandii strain expressing the V-nitrogenase was grown as described above until the cell density started to plateau, when the flask was capped airtight, followed by addition of ¹³CO at a concentration of 15% to the gas phase of this culture. The culture was grown for another 8 h before 250 μl headspace sample was taken and analysed by GC–MS using a Thermo Scientific Trace 1300 GC system coupled to a Thermo ISQ QD (Thermo Electron North America LLC, Madison, WI)4 (link)5 (link). Specifically, a 250 μl gas sample was injected into a split/splitless injector operated at 120 °C in in split mode, with a split ratio of 5. A 1 mm ID liner was used to optimize the sensitivity of gas separation, which was achieved on an HP-PLOT-Q capillary column (0.320 mm ID × 30 m length, Agilent Technologies, Santa Clara, CA) that was held at 40 °C for 2 min, heated to 180 °C at a rate of 10 °C min⁻¹ and held at 180 °C for 1 min. The carrier gas, helium, was passed through the column at a rate of 1.1 ml min⁻¹. The mass spectrometer was operated in electron impact ionization mode and the identities of C₂H₄, C₂H₆ and C₃H₈ were confirmed by comparing their masses and retention times with those of the Scott standard alkane and alkene gas mixture.

FTS trials were performed in a stainless-steel fixed-bed reactor with an inner diameter of 12 mm under high pressure. Typically, the Ru/TiO₂ catalyst (20–40 mesh, 0.3 g) was diluted with quartz sand (20–40 mesh, 0.9 g) and loaded into the reactor. Prior to each reaction, the catalyst was reduced in a H₂ gas flow (20 mL min⁻¹) at the desired temperature (200–600 °C) for 2 h. After the reactor was cooled down, a syngas with a H₂/CO ratio of 2/1 (H₂/CO/Ar = 64/32/4 (v/v/v)) was introduced into the reactor at a flow rate of 15 mL min⁻¹ (space velocity = 3000 mL g_cat⁻¹ h⁻¹). Ar was used as an internal standard to calculate CO conversion and selectivity of CH₄ and CO₂. The reaction was carried out at 160 °C under 2.0 MPa. After passing through a hot trap (120 °C) and then an ice-bath, the gaseous products were analyzed online using an Agilent 7890 gas chromatograph equipped with an HP-PLOT/Q capillary column connected to a flame ionization detector (FID) and a TDX-01 column connected to a thermal conductivity detector (TCD). The data of the catalytic performances of Ru/TiO₂ catalysts were collected at the stable stage after at least 6 h of running. The calculation method for FTS catalytic performance was described in detail in the supplementary information.