Rf values
Rf values
Formula
Rf = distance travelled by compound ÷ distance travelled by solvent front
Real World
Food Standards Agency analysts calculate Rf values when testing supermarket food colourings — an Rf matching Sudan I (a banned carcinogenic dye) triggered a UK-wide product recall in 2005.
Exam Focus
State that Rf values are only valid under identical conditions — same solvent, temperature, and stationary phase.
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