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© www.chemsheets.co.uk A2 1098 17-Jul-16 Type Stationary Phase Mobile Phase Column Powder (SiO2 or Al2O3) solvent Paper (simple TLC) Absorbent paper solvent TLC Powder (SiO2 or Al2O3) on glass/plastic plate solvent Gas Powder (SiO2 or Al2O3) (sometimes coated with liquid) Inert gas (e.g. Ar, N2) © www.chemsheets.co.uk A2 1095 17-Jul-16 In ALL chromatography Substances separated according to relative affinity (attraction) to stationary and mobile phase. If stronger affinity for mobile phase, then move quickly If stronger affinity for stationary phase, the move slowly © www.chemsheets.co.uk A2 1095 17-Jul-16 STATIONARY PHASE: SiO2 (silica) and Al2O3 (alumina) are regarded as a polar powder (due to the nature of their surface structure) MOBILE PHASE: Non-polar solvents: alkanes Polar solvents: water, alcohols e.g. hexane as solvent on silica non-polar molecules would move quickly polar molecules would move slowly © www.chemsheets.co.uk A2 1095 17-Jul-16 © www.chemsheets.co.uk A2 1095 17-Jul-16 Stationary: Powder (SiO2 or Al2O3) Mobile: Solvent For colourless samples: View results under UV light Amino acids can be stained using ninhydrin solvent front 5 cm 4 cm For substance R Rf = 3 = 0.6 5 For substance S Rf = 4 = 0.8 5 3 cm starting line R S © www.chemsheets.co.uk A2 1095 17-Jul-16 © www.chemsheets.co.uk A2 1095 17-Jul-16 “Large scale TLC” Stationary: Powder (SiO2 or Al2O3) Mobile: Solvent FROM: http://www.mun.ca/biology/scarr/4241_RCMchromatogrpahy.jpg FROM: wikipedia © www.chemsheets.co.uk A2 1095 17-Jul-16 • Long coiled tube packed with powder. • Inert gas passes through tube • Retention time = time to travel through tube • Samples often analysed by mass spectrometer as they leave tube Gas chromatogram (e.g. of a fraction of crude oil)