Gc 9a gas chromatograph

Ethylene production rate was measured with a GC-9A gas chromatograph (Shimadzu, Japan) equipped with a GDX-502 column and a flame ionization detector (FID). Each of 30 fresh berries was enclosed in a 500-mL jar and incubated for 3 h. A 5-mL sample of the head-space gas was assayed. ACC content was determined using a previous method (Lizada and Yang, 1979 (link)).

Cecal contents were collected, and the pH was measured immediately with a pH meter (DELTA 320, Shanghai, China). Duodenal contents (2 mL) were mixed with 2 mL distilled water and recovered by centrifugation at 10,000 rpm for 10 min. Subsequently, 1 mL supernatant was collected and mixed with 0.2 mL 20% metaphosphoric acid solution containing 60 mM crotonic acid. VFA levels were determined using a GC-9A Gas Chromatograph (Shimadzu, Japan) with nitrogen as the carrier gas, a flow-rate of 30 mL/min. A CP-WAX capillary column with a length of 30 m, an inner diameter of 0.53 mm, and a membrane thickness of 1 µm was used, and the sample input was 0.6 µL.
Diluted cecal contents (4 mL) were centrifuged for 10 min, and 50 µL supernatant was collected in a 10-mL tube. Phenol and sodium hypochlorite (3 mL each) were added to the supernatant, and the mixture was incubated in a 60 °C water bath for 10 min, followed by immediate cooling. The optical density (OD) at 546 nm was measured, and the concentration of NH₃-N in the cecum was analyzed based on a standard curve of ammonium chloride.

A one-gram fresh sample of primordia was placed in a 10 mL jar and incubated at 25 °C for 24 h. To determine the ethylene concentration, one milliliter of the headspace gas was injected with an air-tight syringe into the GC-9A gas chromatograph (Shimadzu, Kyoto, Japan) equipped with a GDX-502 column and a flame ionization detector (FID). GC parameters were set as follows: temperatures of the column and detector were 70 °C and 140 °C, respectively; and the flow rate of the carrier gas was 40 mL/min.
GA was extracted from primordia and quantified using a previously described method [22 (link)]. One-way ANOVA was used to determine statistically significant differences between samples with IBM SPSS Statistics 20. Differences between samples were considered statistically significant at p < 0.001.

The contents of the cecum were immediately taken out, and the pH value was quickly determined using a DELTA 320 pH meter (Mettler-Toledo, Shanghai, China). Furthermore, 2 mL of distilled water was added to 2 mL of cecal contents and centrifuged at 10,000 rpm for 10 min. Then, 1 mL of supernatant was taken, 0.2 mL of 20% metaphosphoric acid solution containing 60 mM crotonic acid was added, and 0.4 μL of supernatant was taken for injection analysis. The VFA was measured using a GC-9A Gas Chromatograph (Shimadzu, Kyoto, Japan), with nitrogen as the carrier gas and a flow rate of 30 mL/min. The standard solutions were 3.353 mg/mL acetic acid, 1.189 mg/mL propionic acid, and 0.793 mg/mL butyric acid. In addition, after centrifuging 4 mL of cecal content diluent for 10 min, 50 μL of the supernatant was taken in a 10-mL test tube. Subsequently, 3 mL each of phenol and sodium hypochlorite was added to the test tube. The test tube was cooled in a 60°C water bath for 10 min and then immediately with cold water. Then, the optical density (OD) at 546 nm was determined using a UV756 spectrophotometer (UNICO, CA, United States) to calculate the NH₃-N concentration in the cecum. The ammonia standard stock solution contained 32 mg/100 mL NH₃-N.

The collected liquid samples were immediately filtered with 0.45 mm disposable sterile filters (Millipore, Millex GP) and were subsequently injected into freshly vacuumed Labco Exetainers to allow equilibration of gas and liquid phases. The N₂O concentrations in the gas phase of the tube were measured using a Shimadzu GC-9A gas chromatograph equipped with a micro-electron capture detector (ECD) and a flame ionization detector (FID), respectively. Each Labco Exetainer tube was weighed before and after sampling to determine the sample volume collected. This volume, along with the known volume of the Exetainers, enables the dissolved N₂O concentration contained in the original wastewater sample to be calculated15 (link). The detection limit of the liquid phase N₂O concentration is 4.5 × 10⁻⁵mg N/L. The filtered samples were also analysed for the NH₄⁺, NO₃⁻ and NO₂⁻ concentrations using Lachat QuickChem8000 Flow Injection Analyser (Lachat Instrument, Milwaukee, USA). Mixed liquor suspend solid (MLSS) and volatile solids (MLVSS) were measured in triplicates according to the Standard Methods33 . TCOD and TKN in samples collected were analysed according to Standard Methods33 .