Question

Which of the following statements about paper and gas chromatography is correct?
(This question has multiple correct answers)
A.A long retention time in gas chromatography is indicative of a substance with a strong adsorption on to the stationary phase
B.The ${R_f}$ and ${R_t}$ of substance are determined solely by the interaction of the substance with the stationary phase
C.A high ${R_f}$ value is indicative of a substance that absorbs strongly onto the stationary phase
D.A substance with a long retention time in gas – chromatography is likely to have a high Rf value in paper chromatography

Answer 1

Retention time in any type of chromatography is basically the amount of time that the solute takes to pass through the chromatography column. To represent this mathematically, we can say that it is calculated as the time from injection to detection. Another point that must be kept in mind is that the value of retention time is not a fixed value as it influenced by various external factors

Complete step by step answer:
Before we approach the solution of this question, let us understand some basic concepts.
Paper chromatography is an analytical method that is employed for separation of coloured chemicals or substances in a given mixture. It includes basically two components: solvent for the mixture (this acts as the mobile phase), chromatography paper (this acts as the stationary phase). When the paper is placed in the solution, depending on the degree adsorption of the different constituents of the mixture, varied vertical layers of adsorption rise of these constituents can be observed
Similar to paper chromatography, gas chromatography is also used for separation, identification and quantization of compounds in mixture. The major difference being that the mobile phase is usually an inert gas and the stationary phase consists of a packed column in which the packing or solid support itself acts as stationary phase, or is coated with the liquid stationary phase
An ${R_f}$ value or retention factor is used for the determination of the unknown chemicals provided they can interact with other reference substances. This value is dependent on the stationary phase in chromatography. Like ${R_f}$ value, ${R_t}$ also is solely dependent on the stationary phase. Also, ${R_f}$ value does not signify the adsorption strength of a compound but indicates the degree of adsorption of the compound. Also, retention time does not have any relation to the ${R_f}$ value because retention time indicates the adsorption strength and no the degree of adsorption
From the above data, we can say that the following statements about paper and gas chromatography are correct:
A long retention time in gas chromatography is indicative of a substance with a strong adsorption on to the stationary phase
The ${R_f}$ and ${R_t}$ of substance are determined solely by the interaction of the substance with the stationary phase

Hence, Options A and B are the correct options.

Note:
Capillary action makes the solvent travel up the paper, where it meets and dissolves the ink. The dissolved ink (the mobile phase) slowly travels up the paper (the stationary phase) and separates out into different components.