chromatography

stationary phase

• solid/gel/immobilised liquid held by support matrix

chromatographic bed

• configuration holding stationary phase (column/plate)

mobile phase

• liquid or gas which carries sample through stationary phase

mobile phase delivery system

• passes the mobile phase through the chromatographic bed

detection system

• allows visualisation of the analytes

chromatography modes

• normal phase

polar stationary phase

non-polar mobile phase

• reversed phase

non-polar stationary phase

polar mobile phase

elution techinques

• isocratic

a single solvent used through analysis

solvent composition constant through analysis

• gradient

solvent composition changes over time so all species are eluted from column in reasonable time

uses 2 or more solvents that vary in polarity

solvent ratio varied in a programmed way

thin layer chromatography (TLC)

• inert plate coated with thin layer of stationary phase - usually silica or alumina

• mobile phase ascends plate by capillary action

• polar molecules interact strongly with stationary phase so elute slowly

• lipophilic molecules interact weakly with stationary phase so elute quickly

retardation factor (Rf)

Rf = distance from centre of spot to baseline/distance from baseline to solvent-front

preparative column chromatography

• stationary phase packed in glass tube