1. Butan-1-ol is less hydrophobic than octan-1-ol, so falls off the hydrophobic reversed phase HPLC column more quickly?
2. The pK_a of cocaine-H⁺ is 8.6.
   
   • Adjust syrup pH to 10. Add DCM. Cocaine becomes unionised and proportionates into DCM.
   • Keep DCM layer, discard aqueous layer which contains impurities. Add dilute H₂SO₄ at pH 1. Cocaine ionises and proportionates into dilute acid layer.
   • Keep aqueous layer, discard DCM layer with more impurities. Adjust to pH 10 with sodium hydroxide. Cocaine becomes unionised again, and becomes much less soluble in water.
   • Concentrate the solution by rotary evaporation under vacuum until the cocaine precipitates as a solid. Add HCl to the precipitate to form cocaine hydrochloride solution. Concentrate and crystallise solution.
3. α-amanitin is a small peptide. It may well be oxidised by TLC, and could not be purified by GC. Some sort of liquid chromatography is probably indicated, most likely ion exchange FPLC, or similar.
4. DNA is negatively charged, so migrates towards the anode in an agarose gel. All DNA molecules have the same charge density, because this is largely due to the phosphate groups in the backbone, and this increases linearly with length. Hence if electrophoresis separated compounds purely based on their charge density DNA molecules would not be separated. It is the pores in the gel, which provide more resistance to larger molecules, that effect the separation.