Title: Chapter 22 GC & LC 22.1 Gas Chromatography -1 Schematic
1Chapter 22
222.1 Gas Chromatography -1
322.1 Gas Chromatography -2
- Columns open tubular columns
422.1 Gas Chromatography -3
- m.p.(gas) - s.p.
- s.p. solid(using adsorption)ex SiO2
- column ages Si-O-H cause tailing peak.
- 2) s.p. liquid(GLC, using partition)Table 22-1
- Decrease thickness of stationary phase leads to
- Resolution? (H?)
- tr?
- Sample capacity?
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622.1 Gas Chromatography -4
ex
b.p.?
722.1 Gas Chromatography -5
- B) The effects of column polarity on separation
- Like dissolves like
- S.P nonpolar
- b.p. dependent
822.1 Gas Chromatography -6
S.P. Polar
-oneCO -ol OH
922.1 Gas Chromatography -7
- C) Common solid s.p.
- Porous carbon larger molecules bind more
tightly than small ones, flexible molecules bind
more than rigid ones - Molecular sieves retain separate small
molecules H2, O2, N2, CO2, CH4. (Fig. 22-5)
1022.1 Gas Chromatography -8
- packed column vs. open tubular column
higher resolution lower sample capacity
1122.1 Gas Chromatography -9
- Temperature programming
- ? temp of column ? ? v.p. solute,
- ? ? tr
- ? sharpens peaks
- isothermal constant temp.
- temp. programming (gradient)
- raise the column temp. during the separation.
1222.1 Gas Chromatography -10
1322.1 Gas Chromatography -11
1422.1 Gas Chromatography -12
5. Sample Injection-1 1) gasses, liquids, or
solids ? vaporized, not decomposition 2)
injection time ? ? bands broader 3) injected by
syringe (manual or automatic injection)
1522.1 Gas Chromatography -12
1622.1 Gas Chromatography -13
- 5. Sample injection-2
- 4) operation
- .on-column injection (50?)
- best for quantitative analysis
- thermally sensitive compounds
- low resolution
1722.1 Gas Chromatography -14
- b) split injection (350?) (only 0.1-10 sample)
- - concentrated sample
- - high resolution
- - dirty samples
- could cause thermal decomposition
- c) splitless injection (220?) (80)
- - dilute sample
- - high resolution
- solvent trapping (Tsolvent lt 40?)
- cold trapping (Tsolute lt 150?)
1822.1 Gas Chromatography -15
- Detectors
- Qualitative analysis mass spectrometer, IR
- Quantitative analysis area of a chromatographic
peak.
1922.1 Gas Chromatography -16
- Thermal conductivity detector
- -most general way
- -responds to everything
- -not sensitive enough for high resolution.
- Flame ionization detector
- -most popular
- -mainly responds hydrocarbons (C-H)
2022.1 Gas Chromatography -17
- Electron capture detector
- for compounds containing atoms with high electron
affinities. - sensitive for halogen, CO, NOx, orgaometallic
compounds. - Other detectors p 476
-
2122.2 Liquid Chromatography -1
- open, gravity-feed column
- closed column (under high pressure) packed with
micron-size particles. (HPLC) - stationary phase
- adsorption silica (SiO2?xH2O), alumina
(Al2O3?xH2O), - molecular exclusion,
- ion-exchange, ?affinity
2222.2 Liquid Chromatography -2
?compete with ? for binding on s.p.
the more strongly bind to s.p.??eluent
strength ?
2322.2 Liquid Chromatography -3
- 4. Eluent strength Table 22.2
- The more polar solvent
- ? ? eluent strength
- ? ? tr
- 5. Gradient elution increased the eluent
strength during the separation in liquid
chromatography.
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2522.3 High-Performance Liquid
Chromatography (HPLC) -1
2622.3 High-Performance Liquid
Chromatography (HPLC) -2
- 1. Through a closed column, and needs high
pressure. - 2. s.p. particles size ?
- (s.p. ? m.p. faster, i.e. C? in van
Deemter eqn.) - ? resolution ?
-
2722.3 High-Performance Liquid
Chromatography (HPLC) -3
2822.3 High-Performance Liquid
Chromatography (HPLC) -4
2922.3 High-Performance Liquid
Chromatography (HPLC) -5
- 3. Stationary phase
- a) Normal-phase chromatography polar s.p. and
less polar solvent. Eluent strength is increased
by adding a more polar solvent. - b) Reversed-phase chromatography low-polarity
s.p. and polar solvent. Eluent strength is
increased by adding a less polar solvent.
3022.3 High-Performance Liquid
Chromatography (HPLC) -6
- c) Bonded stationary phase.
- polar vs. nonpolar p.461
- d) Optical isomers
- D- L-amino acids
3122.3 High-Performance Liquid
Chromatography (HPLC) -7
- d) Optical isomers separation
- for ant-inflammatory drug Naproxen
3222.3 High-Performance Liquid
Chromatography (HPLC) -8
- 4. Column
- Guard column
- Injection valve
3322.3 High-Performance Liquid
Chromatography (HPLC) -9
- 5. Solvents
- a) Isocratic elution
- elution with single solvent or a constant
solvent mixture - b) Gradient elution
- solvent is changed continuously from a weak
eluent strength to a strong eluent strength by
mixing more and more of a strong solvent to a
weak solvent during the chromatography.
3422.3 High-Performance Liquid
Chromatography (HPLC) -10
A KH2PO4(aq) B CH3CN(l)
3522.3 High-Performance Liquid
Chromatography (HPLC)-11
Reversed-phase column eluent strength ?,
solvent polarity ?, tr ?
3622.3 High-Performance Liquid
Chromatography (HPLC)-12
- The gradient can be used to resolve all peaks
by reducing the time from 2 h to 38 min.