1、 Preparation before startup: Build a solid foundation for safety and stability

Three core preparations need to be made before operation. Firstly, environmental and equipment inspection: ensure that the laboratory temperature is controlled at 15-30 ℃, humidity is 40% -70%, and there is no strong electromagnetic interference or open flames; Check that the appearance of the instrument is undamaged, the gas pipeline is tightly connected, the chromatographic column interface is not loose, the pressure of the carrier gas (usually high-purity nitrogen), gas (hydrogen), and auxiliary gas (air) steel cylinders is normal (carrier gas ≥ 0.4MPa, gas ≥ 0.2MPa), and the leakage test is qualified (apply soapy water to the interface, no bubbles are generated). Next is the preparation of reagents and standards: according to the detection requirements, prepare natural gas standard mixtures of corresponding concentrations (such as methane, ethane, propane and other component standards) to ensure that the standards are within their validity period and the storage conditions meet the requirements. Finally, the instrument is powered on for inspection: turn on the stabilized power supply, confirm that the voltage is stable, and then sequentially turn on the gas chromatograph host, detector (commonly used thermal conductivity detector TCD or hydrogen flame ionization detector FID), and data workstation. Wait for the instrument to complete self inspection without any error prompts before proceeding to the next step.

2、 Instrument calibration: ensuring the accuracy of test results

Calibration is a key step in ensuring data reliability, which is divided into two steps: parameter setting and calibration. Step 1 parameter setting: Set the column temperature program through the workstation (initial temperature of 40 ℃, hold for 3 minutes, heat up to 150 ℃ at 10 ℃/min, hold for 5 minutes, adjust according to component complexity), detector temperature (TCD about 100-150 ℃, FID about 200-250 ℃), carrier gas flow rate (30-50mL/min), and gas to assist gas ratio (FID commonly used hydrogen: air=1:10). Step 2: Calibration of standard curve: Use a microinjection or automatic sampler to inject different concentrations of standard mixture into the injection port in sequence, and record the retention time and peak area of each component. Draw a standard curve with peak area as the vertical axis and concentration as the horizontal axis, calculate the regression equation (R ² needs to be ≥ 0.995), and complete instrument calibration.

3、 Sample analysis: standardize operations to reduce errors

Sample analysis must strictly follow the "sampling injection testing" process. Firstly, sample sampling: a sealed sampler is used to collect natural gas samples to avoid air mixing. After sampling, the sample bottle is quickly sealed to ensure that there is no loss of sample components. Next is the injection operation: if it is a manual injection, the syringe needs to be washed and dried, and after extracting the sample, bubbles should be expelled. Quickly insert it into the injection port and inject the sample (injection time ≤ 1 second), while pressing the collection button on the workstation; If it is automatic injection, simply place the sample bottle into the injection rack and set the injection parameters. Finally, data collection: During the operation of the instrument, observe the chromatogram on the workstation to ensure clear separation of each component peak and no interference from impurities. After all component peaks are completed, stop collecting and save the chromatographic data.

4、 Shutdown and maintenance: extending the service life of equipment

After the inspection is completed, it is necessary to shut down and maintain the equipment according to the specifications. The first step of shutdown process: First, turn off the gas and auxiliary gas, keep the carrier gas flowing, reduce the column temperature and detector temperature to below 50 ℃, then turn off the instrument host and workstation, and finally close the valve of the carrier gas cylinder to release the residual gas in the pipeline. Step 2 equipment maintenance: Wipe the injection port liner and needle with anhydrous ethanol to remove residual samples; Regularly replace the chromatography column sieve plate and check the aging condition of the chromatography column; Clean up detector fouling (TCD can be purged with nitrogen, FID can be burned for cleaning); Record the operation status and maintenance of the instrument, and form an operation log.

The above operation steps need to be flexibly adjusted according to the instrument model and testing standards. Operators need to undergo professional training, be familiar with equipment principles and safety regulations, in order to ensure efficient and accurate testing work.