METRIC: KEY CONCEPTS FOR EXAM
SEPARATION SCIENCE
TLC (Thin layer chromatography)
Mobile phase: suitable liquid solvent, ascends plate via capillary action
Inert plate coated with stationary phase: silica gel, polar Si-OH bonds, alumina gel
Polar molecules interact strongly, elute slower.
Conjugated systems: UV light
Unsaturated systems: Iodine
Ninhydrin: Amino acids
DNP: Aldehydes/ketones
Vanillin: general stain
PMA: universal stain
Rf value = (distance travelled by solute) / (distance travelled by solvent)
Dissolve sample in volatile solvent e.g., DCM
Compounds travel further up the plate if a more polar solvent is used
GC – FID
Gas chromatography – flame ionisation detection
Gas inlets/flow controller : controls the flow of mobile phase/carrier gas through the
instrument
Autosampler: introduction of precise volume of sample
Inlet: vaporisation of the sample, and mixing with the carrier gas can be split or splitless
Column: contains stationary phase, separation of analytes occurs here
Column oven: controls temperature of column
Detector: responds to physiochemical property of the analyte, amplifies the response and
generates an electric signal for the data system to produce a chromatogram
Data system: receives analogue signal from the detector and digitalises it to form the record
of chromatographic separation known as the chromatogram , sample identification and
quantitation
Components of a HPLC instrument
HPLC column – separation of analytes
Detector – measures physiochemical property of analyte/mobile phase as it elutes from the
column
Autosampler – introduces reproducible amounts of sample into the HPLC element stream
Mobile phase reservoir – supply of mobile phase
Pumping system – delivery of mobile phase of desired composition, continuous and pulse
free to HPLC system
How HPLC time can be reduced
Shorter column length
Smaller particles in column
Increase mobile phase flow rate
Decrease column diameter
Melting points
Melting point range: time from which first drop of liquid appears until the entire sample has
melted
Should be within 2 degrees if pure
SEPARATION SCIENCE
TLC (Thin layer chromatography)
Mobile phase: suitable liquid solvent, ascends plate via capillary action
Inert plate coated with stationary phase: silica gel, polar Si-OH bonds, alumina gel
Polar molecules interact strongly, elute slower.
Conjugated systems: UV light
Unsaturated systems: Iodine
Ninhydrin: Amino acids
DNP: Aldehydes/ketones
Vanillin: general stain
PMA: universal stain
Rf value = (distance travelled by solute) / (distance travelled by solvent)
Dissolve sample in volatile solvent e.g., DCM
Compounds travel further up the plate if a more polar solvent is used
GC – FID
Gas chromatography – flame ionisation detection
Gas inlets/flow controller : controls the flow of mobile phase/carrier gas through the
instrument
Autosampler: introduction of precise volume of sample
Inlet: vaporisation of the sample, and mixing with the carrier gas can be split or splitless
Column: contains stationary phase, separation of analytes occurs here
Column oven: controls temperature of column
Detector: responds to physiochemical property of the analyte, amplifies the response and
generates an electric signal for the data system to produce a chromatogram
Data system: receives analogue signal from the detector and digitalises it to form the record
of chromatographic separation known as the chromatogram , sample identification and
quantitation
Components of a HPLC instrument
HPLC column – separation of analytes
Detector – measures physiochemical property of analyte/mobile phase as it elutes from the
column
Autosampler – introduces reproducible amounts of sample into the HPLC element stream
Mobile phase reservoir – supply of mobile phase
Pumping system – delivery of mobile phase of desired composition, continuous and pulse
free to HPLC system
How HPLC time can be reduced
Shorter column length
Smaller particles in column
Increase mobile phase flow rate
Decrease column diameter
Melting points
Melting point range: time from which first drop of liquid appears until the entire sample has
melted
Should be within 2 degrees if pure
