Introduction to the lab course inchromatography
VAK 02-008-6-006
August 27, 2007
Johannes Ranke
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Lab schedule
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Basic GC system
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Carrier gases used in GC
Depending on the detector used:
Helium
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Carrier gases used in GC
Depending on the detector used:
Helium
Hydrogen
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Carrier gases used in GC
Depending on the detector used:
Helium
Hydrogen
Nitrogen
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Standard liquid injector
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Factors limiting sample volume
Injection volume n-hexane methanol water
1 µL 236 µL 764 µL 1712 µL5 µL 1182 µL 3812 µL 8559 µL
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Factors limiting sample volume
Injection volume n-hexane methanol water
1 µL 236 µL 764 µL 1712 µL5 µL 1182 µL 3812 µL 8559 µL
Volume of a 30 m capillary column
Inner diameter Volume
0.53 mm 6.62 mL0.35 mm 2.4 mL0.25 mm 1.47 mL
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Column types in gas chromatography
Packed columns
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Column types in gas chromatography
Packed columns
Open tubular columns (capillary columns)
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Column types in gas chromatography
Packed columns
Open tubular columns (capillary columns)• Porous layer open tubular (PLOT)
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Column types in gas chromatography
Packed columns
Open tubular columns (capillary columns)• Porous layer open tubular (PLOT)• Support coated open tubular (SCOT)
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Column types in gas chromatography
Packed columns
Open tubular columns (capillary columns)• Porous layer open tubular (PLOT)• Support coated open tubular (SCOT)• Wall coated open tubular (WCOT)
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Stationary phase material in capillary GC
Most often, the basic material is dimethylpolysiloxane, with additions of the following elements
Diphenyl polysiloxane
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Stationary phase material in capillary GC
Most often, the basic material is dimethylpolysiloxane, with additions of the following elements
Diphenyl polysiloxane
Phenylmethyl polysiloxane
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Stationary phase material in capillary GC
Most often, the basic material is dimethylpolysiloxane, with additions of the following elements
Diphenyl polysiloxane
Phenylmethyl polysiloxane
Cyanopropylmethyl polysiloxane
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Stationary phase material in capillary GC
Most often, the basic material is dimethylpolysiloxane, with additions of the following elements
Diphenyl polysiloxane
Phenylmethyl polysiloxane
Cyanopropylmethyl polysiloxane
Other important materials are based on paraffine or
polyethyleneglycol.
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Most important GC detectors
Flame ionisation detector (FID)
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Most important GC detectors
Flame ionisation detector (FID)
Heat conductivity detector (HCD)
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Most important GC detectors
Flame ionisation detector (FID)
Heat conductivity detector (HCD)
Electron capture detector (ECD)
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Most important GC detectors
Flame ionisation detector (FID)
Heat conductivity detector (HCD)
Electron capture detector (ECD)
Nitrogen phosphorus detector (NPD)
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Most important GC detectors
Flame ionisation detector (FID)
Heat conductivity detector (HCD)
Electron capture detector (ECD)
Nitrogen phosphorus detector (NPD)
Mass spectrometric detector (MSD)
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Elution techniques
A + B
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Elution techniques
A
B
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Elution techniques
A
B
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Elution techniques
Time [min]
Det
ecto
r si
gnal
0 2 4 6 8 10
A
B
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Equilibrium based separation
tM
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Equilibrium based separation
tMtR
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Equilibrium based separation
tMtR
k′ = nSnM
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Equilibrium based separation
tMtR
k′ = nSnM=t̄St̄M
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Equilibrium based separation
tMtR
k′ = nSnM=t̄St̄M=tR−tMtM
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Equilibrium based separation
tMtR
k′ = nSnM=t̄St̄M=tR−tMtM
k′ = cS·VScM·VM
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Equilibrium based separation
tMtR
k′ = nSnM=t̄St̄M=tR−tMtM
k′ = cS·VScM·VM
= K · VSVM
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Equilibrium based separation
tMtR
k′ = nSnM=t̄St̄M=tR−tMtM
k′ = cS·VScM·VM
= K · VSVM
tM = F · VM
tR = F · VR
k′ = nSnM=t̄St̄M=tR−tMtM=VR−VMVM
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Equilibrium based separation
tMtR
k′ = nSnM=t̄St̄M=tR−tMtM
k′ = cS·VScM·VM
= K · VSVM
tM = F · VM
tR = F · VR
k′ = nSnM=t̄St̄M=tR−tMtM=VR−VMVM
VR ≈ VM + K · VS
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Gaussian peaks
t
S
tR
b b
2σ
b b
wb = 4σ
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Gaussian peaks
t
S
tR
b b
2σ
b b
wb = 4σ
N = ( tRσ )2
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Gaussian peaks
t
S
tR
b b
2σ
b b
wb = 4σ
N = ( tRσ )2
N = 16 · ( tRwb )2
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Gaussian peaks
t
S
tR
b b
2σ
b b
wb = 4σ
N = ( tRσ )2
N = 16 · ( tRwb )2
N = 8 · ln 2 · ( tRw0.5 )2
b b
w0.5
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Peak dispersion
Injection
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Peak dispersion
Injection
Dispersion in connecting tubes/capillaries
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Peak dispersion
Injection
Dispersion in connecting tubes/capillaries
Dispersion in columns
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Peak dispersion
Injection
Dispersion in connecting tubes/capillaries
Dispersion in columns
Dispersion caused by signal detection
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Dispersion in columns
van-Deemter equation:
H = A + B/v + C v
Eddy diffusionA = 2λdR
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Dispersion in columns
van-Deemter equation:
H = A + B/v + C v
Eddy diffusionA = 2λdR
Longitudonal diffusionB = 2ΨDM
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Dispersion in columns
van-Deemter equation:
H = A + B/v + C v
Eddy diffusionA = 2λdR
Longitudonal diffusionB = 2ΨDM
Lateral diffusion, disequilibriumC = K1 · R · (1 − R) · d
2f/DS + K2/DM
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Influence of N on resolution
0 1 2 3 4 5 6
05
1015
N = 4000
Time [min]
0 1 2 3 4 5 6
05
1015
N = 1000
Time [min]
0 1 2 3 4 5 6
05
1015
N = 500
Time [min]
0 1 2 3 4 5 6
05
1015
N = 100
Time [min]
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Van Deemter plot
0 2 4 6 8
01
23
4
velocity v
Pla
te h
eigh
t H
van Deemter curve H = A + B/v + c vEddy diffusion ALongitudonal diffusion B/vLateral diffusion c v
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