In chromatography, which of the following statements is incorrect for R$$_f$$?

First, let us recall the definition of the retention factor, commonly written as $$R_f,$$ which is used for comparing how far a substance travels on a chromatographic plate.

The formula is stated as

$$ R_f=\frac{\text{Distance travelled by the centre of the spot of the solute}}{\text{Distance travelled by the solvent front}} $$

Since the solute spot can never move farther than the solvent front, the numerator is always smaller than or at most equal to the denominator. Therefore, from the above formula we immediately obtain

$$ 0 < R_f \le 1 . $$

Now we analyse each option one by one in the light of the definition.

Option A: “Higher $$R_f$$ value means higher adsorption.” We know that stronger adsorption to the stationary phase causes a compound to move more slowly; hence the distance in the numerator becomes smaller. This gives a smaller $$R_f,$$ not a higher one. Therefore, a higher $$R_f$$ actually corresponds to lower adsorption. So the statement in Option A is wrong.

Option B: “The value of $$R_f$$ cannot be more than one.” From the inequality $$0 < R_f \le 1$$ derived above, this statement is perfectly true. Hence Option B is correct and therefore not the answer we seek.

Option C: “$$R_f$$ value depends on the type of chromatography.” Different chromatographic techniques (paper, thin-layer, column, etc.) employ different stationary and mobile phases, thus altering adsorption-desorption equilibria. Consequently, $$R_f$$ indeed varies with the type of chromatography. So Option C is a correct statement.

Option D: “$$R_f$$ value of dependent on the mobile phase.” Changing the polarity or composition of the mobile phase directly affects how far a solute moves, hence changing $$R_f.$$ Therefore this statement is also correct.

Among the four given choices, only Option A makes an incorrect claim about $$R_f.$$

Hence, the correct answer is Option A.