Separation of analytes
Separation of analytes - contextAnalyte mixtures and separation - 1Analyte mixtures and separation - 2Analyte mixtures and separation - 3Introduction to chromatographyChromatographic columnsPrinciple setup of a chromatographic unitExample of separationChromatographic system - 1Chromatographic system - 2Standard gas chromatograph(Old) liquid chromatography unit(New) liquid chromatography unitHPLC columnsComparison GC and HPLC
SelftestProblems
End of chapterComparison GC and HPLC
| (high performance) liquid chromatography (HP) LC | gas chromatography GC | |
| mobile phase |
normal phase LC: non-polar liquid; reversed phase LC: polar liquid | gas (typically He on N2) no air, because the oxygen would oxydize the stationary phase at higher temperatures |
| stationary phase | 1.5 to 5 μm diameter particles; reversed phase LC: coated with apolar carbon chains that may bear a functional group |
heat-resistant polymer films (nonpolar to bipolar, choice is analyte-dependent) |
| operating conditions | high pressure (up to 400 bar); room temperature; solvent gradients | slight overpressure; gradients in temperature (T max = 300 ° C) |
| column geometry | length: 0.03 to 0.25 m steel cylinder; inner diameter: 2-5 mm ; thickness stationary phase: 0.2-1.0 μm |
length
= 60m; |
| analytes | too big or too polar (i.e., too strong VdW and H-bond interactions) to elute on GC columns |
thermally stable; sufficiently small and apolar to elute in reasonable time |
