The purpose of flash column aging is to completely remove residual solvents and certain volatile substances in the packing; on the other hand, it is to promote the even and firm distribution of the fixative on the surface of the support. And the new gas chromatography column must be aged.
After the packed flash column is connected to the instrument, it should be tested for pressure and leak first, and then purged with carrier gas at a constant temperature for several hours and then subjected to analysis. This is generally called the aging process of the column.
The purpose of aging is to drive away residual solvents, low-boiling impurities, low-molecular-weight stationary liquids, etc. of the stationary phase so that the baseline of the recorder is straight, and at the aging temperature, the stationary liquid has a redistribution process on the surface of the support, thereby coating more uniform and firm. The packed flash column, after aging for a period of time, the column efficiency and performance are stable, so it can be used.
Aging steps: Turn on the power switches of the nitrogen, hydrogen, and air generators, and the output pressure is stable at about 0.4Mpa. Turn on the nitrogen switch of the gas purifier of the chromatograph. When the front pressure of the chromatograph carrier gas B rises and stabilizes for about 5 minutes, turn on the power switch of the chromatograph. Set the temperature of each working part, the initial temperature of the oven is 50°C, and the sampler and detector are both 250°C. After the detector temperature rises above 100℃, turn on the hydrogen and air switches on the purifier, the hydrogen gas of the chromatograph is stable at 0.1Mpa, and the air pressure is about 0.15Mpa.
Observe that the baseline voltage should be high after the hydrogen flame is lit. Before the ignition. There should be blue letters on the bottom left of the display to display the current-voltage value and time. After the baseline is stable, enter the sample and click the “Start” button or press the shortcut button next to the chromatograph to analyze the chromatographic data. When the analysis is over, click the “Stop” button, and the data is automatically saved. First, turn off the hydrogen and air sources to extinguish the fire by the hydrogen flame detector.
For gas-liquid chromatography columns, it generally includes synthesis of stationary phase, the configuration of the coating solution, treatment of the inner wall, static or dynamic coating, and finally chemical cross-linking and aging.
To prepare a packed column chromatography column, you need to choose a suitable column tube, determine the type of stationary phase commonly known as filler, and the filler used to fix the filler, such as glass wool, quartz wool, or metal mesh. The most commonly used column tubes are stainless steel column tubes and glass column tubes. Stainless steel column tubes are the material of choice for column tubes due to their durability and ease of winding.
However, they have an adsorption effect on polar substances, which requires more inert glass column tubes to replace them. You can also choose to process a more complex stainless steel column tube lined with glass, or a stainless steel column tube processed by various new passivation technologies. It is reported that some stainless steel column tubes can reach the inertness of glass or quartz. In addition, for some samples with strong adsorption activity, especially for low-concentration analysis, PTFE column tubes are often used, such as the analysis of ppm-level H2S gas.
After determining the chromatographic column, you need to select the type of stationary phase. According to the characteristics of the sample to be analyzed, decide whether to use an adsorbent or a carrier coated with a stationary liquid as the stationary phase. The adsorbents commonly used in gas-solid chromatography columns include alumina, silica gel, porous polymers, molecular sieves, and carbon-based materials. There are many substances that can be used as stationary liquids for gas-liquid distribution chromatographic columns, nearly a thousand have been used, and new applications are constantly emerging, such as chiral stationary liquids, ionic liquids, etc.