1. What would be the effect of the following errors in chromatographic work? a. The solvent level in the developing chamber is higher than the spotted sample. The sample spot must not be lower than the solvent system because the sample spot will be dissolved in it. b. Too much sample is applied to the paper Too much sample applied to the paper will result to tailing because of its too much concentration in a location. c. The paper is allowed to remain in the chamber after the solvent front has reached the top of the plate. The paper will be saturated resulting to difficulty in determining the dispersion of the compounds. 2. What is the purpose of adding two drops of acetic acid in thin later chromatography of plant pigments? The addition of acetic acid prevents streaking. Increasing the acidity of the solvent system increases its eluting strength as it has a greater tendency to displace polar compounds further up in the plate. 3. Correlate the structures of the standard food dyes to their relative position in the paper chromatogram. The pigments in red and yellow dye which have amine and phenol on its structure doesn’t move further up the filter paper compared to Brilliant Blue CFC which is located closest to the solvent front. 4. What are the identities of your unknowns in paper chromatography of food dyes? How did you arrive at this conclusion? 5. Differentiate normal phase chromatography from reverse phase chromatography. From which of the two governs the experiment you did in thin layer chromatography of plant pigments? How did you say so? Reversed-phase chromatography makes use of mobile phase which is significantly more polar compared to its stationary phase while normal phase chromatography uses a 100% organic mobile phase (hydrophobic). The reverse phase chromatography governed the experiment. Since the stationary phase is hydrophobic, the compound that have hydrophilic properties will have greater affinity to the mobile phase and the hydrophobic compounds tend to adsorb to the hydrophobic stationary. Cite as: IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook.
