Example
For example, if glucose and fructose are expanded in n-butanol-acetic acid-water (4∶1∶5) at 20℃, R of 0.18 and 0.23 can be obtained, respectively.f value is expanded in ethyl acetate-pyridine-water (2:1:1) to obtain Rf values of 0.28 and 0.32, respectively. If the filter paper, solvent temperature, etc. remain constant, various substances exhibit specific Rf values, which become extremely important constants for identifying substances.
Influencing factors
It is related to the polarity of the tested substance and the polarity of the developing agent, as well as the adsorption capacity of the solid phase adsorbent and the elution capacity of the eluent.
Chromatography definition
Chromatography is an important method for separating substances. The solubility of the two different substances in the chromatographic fluid is different, resulting in different crawling speeds, and they can be separated after a period of time.
When doing this experiment, there are the following points to note.
1 Put an appropriate amount of the chromatography solution, the standard is to keep the chromatography process neither volatile (so the chromatography process is best to cover), nor without marking.
2 The chromatography time should not be too long, otherwise the Rf of a liquid cannot be measured when it climbs to the highest point. It is best to do a small test before the experiment to determine that the liquid climbs. Time to the highest point.
3 After the chromatography, draw the area (circular) with a pencil as soon as possible to prevent the color from fading. When waiting for measurement, measure the distance from the engraved line to the center of the circle and follow the formula.