Experimental precautions

A list of experimental precautions for paper chromatography experiments.

• Use a good quality pencil for drawing the reference line so that the mark does not dissolve in the solvent. If you used a pen the mark would dissolve.

• Dip the paper strip into the solvent so that the spot of the mixture is above the solvent level. This prevents the spots from streaking across the entire paper or not appearing at all.

• Place the paper strip in the jar so that the bottom of the strip is perfectly horizontal when it touches the solvent surface. This will ensure that the solvent front is straight and not a zig-zag. This prevents one spot from being ahead of the others and inaccurate calculation of the R_f value.

• While spotting the test solution on the paper, do not allow the spots to spread. Use a finely drawn capillary to put the spot on the paper for a very short amount of time. This prevents streaking and merging of spots, which would lead to inaccurate calculation of the R_f value or make it difficult to distinguish two spots.

• Ensure that the filter paper strip hangs freely in the jar.

• Once the experiment is set, do not disturb the jar as long as the chromatogram is being developed. This prevents splashes of solvent and prevents the solvent front from moving at an angle.

• Keep the jar covered with the lid when the chromatogram is being developed. This allows for a saturated solvent atmosphere inside the jar and prevents solvent evaporation which would change the ratio of solvents in the solvent mixture.

• Make sure the paper strip is perfectly dry before developing the spots.

• Handle solvents with care.

References:

• NCERT Chromatography handbook