This question is about thin-layer chromatography (TLC).
A forensic scientist is analyzing the ink from a suspected forged document using thin-layer chromatography (TLC).
Plan an investigation to determine the Rf R_f\,Rf value of the primary blue dye component in this ink sample.
Your plan should describe how to use:
- a silica-coated TLC plate
- a developing chamber (beaker) with a watch glass cover
- a suitable mobile phase solvent (such as an ethyl acetate/hexane mixture)
- a capillary tube containing the dissolved ink extract
Your description must include:
- how to set up the apparatus and run the chromatogram safely and effectively
- the measurements required, referencing the variables x x\,x and y y\,y shown in the diagram below
- the formula used to calculate the final Rf R_f\,Rf value.
Two forensic scientists analyzed the same ink sample on identical silica TLC plates but obtained different Rf R_f\,Rf values for the primary blue dye.
Which of the following differences in their investigations would result in different Rf R_f\,Rf values?
- Using a wider developing chamber (beaker)
- Leaving the TLC plate in the chamber for a longer period of time (while the solvent front remains below the top of the plate)
- Changing the ratio of ethyl acetate to hexane in the solvent mixture
- Using a longer TLC plate
In thin-layer chromatography, separation occurs as the mobile phase travels up the stationary phase.
What is the stationary phase in the forensic scientist's TLC setup described in part (a)?
- Ethyl acetate/hexane solvent mixture
- Silica coat on the plate
- Watch glass cover
- Dissolved ink sample