Chromatography Flashcards
• is an analytical technique commonly used for separating a mixture of chemical substances into its individual components, so that the individual components can be thoroughly analyzed
Chromatography
Basic Components of Chromatography (8)
Mobile phase/ carrier
Stationary phase/ adsorbent
Colume
Eluate
Eluent
Elution
Analyte
Retention time or factor
• Gas or liquid
• Solvent moving through the column
• Carries the sample
• Mobile phase or carrier
– holds the stationary phase
Column
– separated components
Eluate
• Fluid or substance that enters the column and moves the analyte
Eluent
• Solid or liquid
• Where the mobile phase flows
Stationary phase or adsorbent
• The process of washing out a compound through a column using a suitable solvent
Elution
• Mixture whose individual components have to be separated and analyzed
• Analyte
• The time it takes for a compound or analyte to elute
• Retention time or factor
Chromatographic techniques may be classified according to their mobile phase:
• Gas chromatography
• Liquid chromatography
• is useful for compounds that are naturally volatile or can be easily converted into a volatile form
Gas Chromatography
• separating compounds based primarily on their volatility
Gas Chromatography
Two types:
• Gas-Liquid Chromatography:
• Gas-Solid Chromatography:
: based on partition
: based on adsorption
• Gas-Liquid Chromatography
• Gas-Solid Chromatography
• Packed columns or Capillary columns
• Glass or stainless steel (packed) or thin-fused silica (capillary)
• Packed columns are filled with inert particles such as diatomaceous earth or porous polymer or glass beads coated with a nonvolatile
liquid (stationary) phase • liquid stationary phase must be nonvolatile at the temperatures used, must be thermally stable, and must not react chemically with the solutes to be separated
Columns
Gas Chromatography
TWO DETECTORS:
• Thermal conductivity
• Flame ionization detector
• contain wires (filaments) that change electrical resistance with change in temperature
• Thermal conductivity
• more sensitive than TC detectors
• small hydrogen flame and collector electrode
• As the sample burns, ions form and move to the charged collector
Flame ionization detector
• Uses lower temperatures for separation achieving better separation of thermolabile compounds
• Easier to recover a sample compared to GC
• The mobile phase can be removed, and the sample can be processed further or reanalyzed under different conditions.
Liquid Chromatography
Liquid Chromatography
Types of separation technique:
• Adsorption
• Partition
• Steric exclusion
• Affinity
• Ion-Exchange
liquid–solid chromatography
ADSORPTION
competition between the sample and the mobile phase for the adsorptive sites on the solid stationary phase
ADSORPTION
stationary phase can be acidic polar (e.g., silica gel), basic polar (e.g., alumina), or nonpolar (e.g., charcoal)
ADSORPTION
Disadvantage:
strong retention of many compounds by the supports, making them difficult to elute from the column.
ADSORPTION
Liquid-liquid Chromatography
PARTITION
separation of substances according to their solubility in an organic/non-polar solvent and in an aqueous/polar solvent
PARTITION
“like dissolves like”
PARTITION
Polar molecules remain in the aqueous solvent; nonpolar molecules are extracted in the organic solvent
PARTITION
Variation of L-S chromatography
STERIC EXCLUSION
A.k.a. size exclusion chromatography
STERIC EXCLUSION
Separation based on size and shape
STERIC EXCLUSION
Solid phase is packed with porous material (beads) that separates solutes according to size
STERIC EXCLUSION
Widely used for the separation of proteins, peptides and nucleic acids
ION EXCHANGE
Solute ions of the opposite charge in the mobile liquid phase are attracted to the resin by electrostatic forces
ION EXCHANGE
use of a resin (stationary solid phase) for covalent attachment of anions or cations onto it
ION EXCHANGE
antigen and antibody, enzyme and substrate, receptor and ligand, protein and nucleic acid
AFFINITY
utilizes the specific interaction between one kind of solute molecule and a second molecule that is immobilized on a stationary phase
AFFINITY
most selective type of chromatography employed
AFFINITY
CHROMATOGRAPHIC PROCEDURES
Thin-layer chromatography
High-performance liquid chromatography
Most commonly used as a semiquantitative screening test
THIN-LAYER CHROMATOGRAPHY
A thin layer of sorbent, such as alumina, silica gel, cellulose or cross-linked dextran, is uniformly coated on a glass or plastic plate
THIN-LAYER CHROMATOGRAPHY
Variant of column chromatography
THIN-LAYER CHROMATOGRAPHY
Uses pressure for fast separations, controlled temperature, in-line detectors and gradient elution techniques
HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY
BASIC COMPONENTS OF HPLC:
Pumps
Columns
Sample injectors
Detectors
Recorders
Forces the mobile phase through the column at a much greater velocity
Pump
3 types of pums in hplc
Mechanical reciprocating pump
Pneumatic pumps
Hydraulic amplifier pumps
– most widely used pump
Mechanical reciprocating pump
– pump for preoperative purposes
Pneumatic pumps
– pump that is no longer commonly used
Hydraulic amplifier pumps
Long stainless steel
– most common
Columns
Silica gek
Can be used to introduce the sample into the path of the mobile phase that carries it into the column
Sample injectors
Best and most widely used
High reproducibility
Used at high pressures
Loop injector
Monitor the eluate as it leaves the column
Produce an electronic signal proportional to the concentration of each separated component
Detectors
3 detectors
Spectrophotometer
Photodiode array
Amperometric or electrochemical detector
– detect absorbances of visible or UV light
Spectrophotometers
used for spectral comparisons and compound identification and purity and for drug analysis in urine
Photodiode array
measures current produced when the analyte of interest is oxidized or reduced at some fixed potential set between a pair of electrodes
Amperometric or electrochemical detector
Used to record detector signal versus the time mobile phase passed through the instrument, starting from the time of sample injection
Recorders
Recorder
The graph is called_________
________is proportional to concentration of the compounds that produced the peaks
chromatogram
Peak area
GL Chromatography is based on
Partition
GS Chromatography is based on
Adsorption
Basic components pf Gas Chromatography
Column
Detectors
Columns used in gas chromatography
Packed column - glass/ stainless steel
Capillary column - thin-fused silica
These type of column are filled with diatomaceous eart/ porous polymer/ glass beads
Packed column
Other name for steric exclusion
Size exclusion
Steric exclusion is a variation of
LS chromatography