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How does the Rf value change when changing the eluent composition?
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Natasha Rodriguez
How does the Rf value change when changing the eluent composition?
As, mentioned by Jan Increasing the polarity of solvent will result in increase in Rf value as the compound in even for polar or nonpolar compound, this is the rule of thumb in most cases, may be except do exist i don't know about it. But for my experience in the laboratory polarity result increase in Rf value.
As, mentioned by Jan Increasing the polarity of solvent will result in increase in Rf value as the compound in even for polar or nonpolar compound, this is the rule of thumb in most cases, may be except do exist i don't know about it. But for my experience in the laboratory polarity result increase in Rf value.
The most important interaction is that of the mobile phase with the stationary phase. If you increase the mobile phase’s polarity, that interaction will increase, decreasing the interaction of the solute with the stationary phase. Therefore, a higher ethyl acetate content in the mobile phase will increase $R_f$ values.
The most important interaction is that of the mobile phase with the stationary phase. If you increase the mobile phase’s polarity, that interaction will increase, decreasing the interaction of the solute with the stationary phase. Therefore, a higher ethyl acetate content in the mobile phase will increase $R_f$ values.
What if the molecule is extremely non-polar and the interactions with mobile phase are dominant? Is this possible? Could I have a reference for your response?More
@Uros If the interactions with the mobile phase are dominant, the $R_f$ value in pure hexane will be $> 0.5$. Source: Selling my soul to the chemistry lab for the last five years.More
@adosar We basically cannot predict the $R_f$ value of a compound in a different solvent (i.e. if it has $R_f=0.5$ in $3:1$ that only tells me the $R_f$ value will be lower in $4:1$, I cannot give a specific value; both solvents $\text{hexane}:\ce{EtOAc}$). We can, of course, perform multiple TLC experiments and compare the outcomes which leads to the rule of a more polar ratio of the same solvents always giving a higher $R_f$ value for compounds.More
Part two: Yes, in these lab years I had my fair share of compounds whose $R_f$ values in pure isohexane were larger than $0.8$ (which technically makes them impossible to isolate in standard silica chromatography). No matter which other mobile phase mixture I used, their $R_f$ value never sank.More
As, mentioned by Jan Increasing the polarity of solvent will result in increase in Rf value as the compound in even for polar or nonpolar compound, this is the rule of thumb in most cases, may be except do exist i don't know about it. But for my experience in the laboratory polarity result increase in Rf value.
As, mentioned by Jan Increasing the polarity of solvent will result in increase in Rf value as the compound in even for polar or nonpolar compound, this is the rule of thumb in most cases, may be except do exist i don't know about it. But for my experience in the laboratory polarity result increase in Rf value.
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The most important interaction is that of the mobile phase with the stationary phase. If you increase the mobile phase’s polarity, that interaction will increase, decreasing the interaction of the solute with the stationary phase. Therefore, a higher ethyl acetate content in the mobile phase will increase $R_f$ values.
The most important interaction is that of the mobile phase with the stationary phase. If you increase the mobile phase’s polarity, that interaction will increase, decreasing the interaction of the solute with the stationary phase. Therefore, a higher ethyl acetate content in the mobile phase will increase $R_f$ values.
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