Chromatography retention parameter seminar (1)
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Rf value is defined as the distance traveled by a compound divided by the distance traveled by the solvent front. It represents the ratio of the path length of the compound spot to the path length of the solvent front. The Rf value depends on how much time a compound spends in the mobile phase versus the stationary phase - compounds that spend more time in the mobile phase will have higher Rf values closer to 1, while those that spend more time in the stationary phase will have lower Rf values closer to 0. For Rf values to be consistent, the solvent system, adsorbent, temperature, thickness of adsorbent, and amount of material must remain constant. Rf values can provide evidence about a compound
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Chromatography retention parameter seminar (1)
- 1. By Lalita Dahiwade Pharmaceutical chemistry
- 20. Chromatographic retention parameter for TLC-Rf factor It is defined as the distance travelled by compound divided by the distance travelled by solvent. The basic characteristic of the position of analytes spot on TLC chromatograms is the Rf value (retardaction factor). Rf value is the ratio of the path length that has crossed spot of solute from the start line Ss and path length Sf of the solvent front. Rf=
- 22. If the solute spends more time in the mobile phase, then its chromatographic spot position is closer to the front of solvent and its Rf value is even higher (maximum value of the Rf parameter is 1). Whereas if the solute spends more time in the stationary phase, then the position of his spots closer to the start line, and its Rf value is less.
- 23. The rf of compound is constant from one experiment to the next only if the chromatography conditions below are constant: -solvent system; -adsorbent; -temperature - thickness of the adsorbent; -amount of material. The Rf can provide corroborative evidence as to the identify of a compound. If two substances have same Rf value, they are likely the same compound. If they have different Rf values, they are definitely different compounds.