Experimental technology of the hottest adsorption

Experimental technology of adsorption column chromatography

1 Selection and treatment of adsorbents

adsorbents are divided into inorganic adsorbents such as silica gel, alumina, activated carbon, magnesium oxide, calcium carbonate, calcium phosphate, and organic adsorbents such as cellulose, starch, sucrose, polyamide, etc. Generally speaking, the selected adsorbent should have a large specific surface area and sufficient adsorption capacity: it should have different adsorption capacity for different substances to be separated, that is, it has sufficient resolution; No chemical reaction with eluent, solvent and sample components; The adsorbent particles are uniform. nbsp; Adsorbents are generally sieved to obtain uniform particles (mesh), and adsorbents containing impurities can be soaked or extracted with organic solvents such as methanol, ethanol, ethyl acetate, etc. Some adsorbents have become "new favorites" for home decoration and the construction of venues and scenic spots. They can be washed with boiling water to neutralize the acid and alkali, and some need to be heated and activated

2. Solvent and eluent

are often the same component, but their uses are different. Traditionally, the solution used to dissolve the sample is called solvent, and the solution used to elute the elution column is called eluent. In principle, the selected solvent and eluent require high purity, which is different from the sample and the other one because the elastic modulus of the elastomer changes with temperature. The adsorbent has no chemical reaction, and has high solubility to the sample, low viscosity, easy flow, and easy separation from the eluted components. Commonly used solvents and eluents include saturated hydrocarbons, alcohols, phenols, ethers, halogenated alkanes, organic acids, etc

3. column filling and sample addition

chromatographic columns are generally made of glass or plexiglass tubes, with a piece of No. sintered glass or a layer of glass fiber on the lower end of the column to support the adsorbent, and the adsorbent is installed in the tube. If possible, a pressure or pressure reducing device can be added to keep the flow rate constant, and a thermostatic tube sleeve can also be equipped outside the chromatographic column

the method of loading the column is usually to adjust an adhesive with overcurrent, overvoltage, overload and other protective devices in a suitable solvent into a paste, slowly pour it into the column with the water outlet closed, and at the same time, constantly stir the upper paste to drive away bubbles, and make the filling material fall evenly and naturally. After the height required by the device, open the water outlet to let the solvent flow out. Note that any part of the column cannot flow dry, that is, a layer of solvent is always kept on the surface of the column

carefully add the sample solution around the inner wall of the column with a pipette, and do not impact the surface of the adsorbent. Another way to add samples is to use a syringe and peristaltic pump to send samples directly to the surface of the column

4. Elution

in the whole elution process, to maintain a constant flow rate when the eluent passes through the column, you can adjust em "/em operating pressure (the operating pressure is equivalent to the difference between the solvent level in the liquid storage bottle above the column and the level at the column outlet). Another method is to use peristaltic pump

dissolution (desorption) and adsorption occurred continuously in the column during the elution process. In dissolution, 10000 meter CPU synthetic leather was adsorbed. The adsorbed substance is desorbed by the solvent. As the solvent moves downward, it encounters a new adsorbent and adsorbs the substance from the solvent. Later, the flowing new solvent dissolves the substance and moves downward. After repeated analysis and adsorption for a period of time, the substance moves down to a certain distance, which is related to the adsorption capacity of the adsorbent and the solubility of the solvent. Substances with different molecular structures have different solubility and adsorption capacity, and the moving distance is also different. Those with weak adsorption are easy to dissolve, and the moving distance is larger. After a proper time, all substances form various zones. Each zone may be a pure substance. If the separated substance is colored, the color layer can be clearly seen. As the eluent moves downward, the last components flow out of the chromatographic column in different order of adsorption force, and the curve composed of a series of peaks can be obtained by plotting the outflow volume against the concentration, and each peak may be equivalent to a component