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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