Chromatography
- Created by: SamDavies
- Created on: 02-01-19 18:52
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- Chromatography
- Paper chromatography
- Solid phase: cellulose (polar) Mobile phase: Any (usually H2O/EtOH mix)
- Separates ink based on affinity of the colours to paper (cellulose)
- Thin layer chromatography
- Solid phase: silica (polar) Mobile phase: organic solvent
- Rf value = the distance travelled by the compound / the distance travelled by the eluent
- Increasing the polarity of the solvent will increase the distance of the compound travelled because there is now a higher affinity for the mobile phase
- Not good for higher quantities of material
- Column chromatography
- Identical principle to TLC but allows for higher quantities of material
- Solid phase: silica column Mobile phase: organic solvent
- Most non-polar component will elute off first
- HPLC
- Uses reverse phase chromatography (inert non-polar stationary phase and polar mobile phase)
- Starts with an aqueous eluent, adding more organic components at intervals until the eluent is 100% organic (gradient)
- Solvent is pumped through a column with C18 silica with the sample added into the stream
- Attached to a detector at the end which analyses drops of the sample OR to a UV-Vis spectrometer
- Non-UV absorbing components will not be observed
- Retention time: the time taken to reach the other end of the HPLC machine from injection
- Rt will always be the same for the same compound provided the solvent system remains the same
- Uses reverse phase chromatography (inert non-polar stationary phase and polar mobile phase)
- LCMS
- Couples HPLC with mass spec
- LCMS is only quantitative in relation to standards
- Paper chromatography
- Gradient solvent systems change the polarity of the solvent as the sample is run through the HPLC machine
- Isocratic solvent systems (i.e. the same solvent) produce broad peaks with lower max concentrations
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