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Gas Chromatography

2004.

Kim, Wang-Yu Ph.D.Interface Engineering Co., Ltd.

- 이론과 실제 -

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GC 의 정의• 두개의 상 ( 고정상 , 이동상 ) 사이에서

혼합물 각각의 성분이 분배 ( 혹은 흡착 )되는 정도가 다른 성질을 이용하여 각각의 성분을 분리하는 크로마토그래피 기술이다 . 이동상으로는 혼합물과 반응하지 않는 기체를 사용하는 것이 HPLC 와 크게 다른 점이다 .

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GC vs. LC

Mobile phase

Sample state

Gas Liquid

Gas Liquid

Stationary phase

Liquid

Liquid or solid

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Outside GC

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Inside GC

Injecting and vaporizing

Separating

Detecting

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Septum

Nut

Graphite ferrule

Injection Port

Inlet liner

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Septum

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Ferrule

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1. Stationary phase2. Inner Diameter(mm)3. Length(m)4. Film Thickness(um)

Capillary columns

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FIDFlame Ionization Detector

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GC Column 종류 ( 단면 )

PackedOpen (Capillary)

Regular

Bead

ColumnPorous

Layer

Bead

Conventional

Packed and

Micropacked

Porous Layer

Open Tube(PLOT)

Wall Coated

Open Tube(WCOT)

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Capillary Column Types

Wall Coated Open Tubular (WCOT)

Liquid Phase

Porous Layer Open Tubular (PLOT)

Carrier Gas

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2. Inner Diameter(mm)3. Length(m)4. Film Thickness(um)

1. Stationary phase

GC column 의 특성

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Polarity

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Polarity Solubility

Phase = Solute High

Phase Solute Low

High solubility = High retention and capacity

POLARITY

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DISPERSION INTERACTIONKcal/mole

DB-1 (non-polar)0 2 4 6 8 10

Benzene

Phenol

C10 C12

8.1

11.9

10.9 11.9

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DIPOLE INTERACTIONCompounds With Dipole

Differences

C=CCl Cl

H H

C=CCl

Cl

H

H

1,2-dichloroethylene 1,1-dichloroethylene

• Smaller differences require a stronger dipole phase

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HYDROGEN BONDING INTERACTIONExample Compounds

•Strong: alcohols, carboxylic acids, 1° and 2° amines

•Moderate: aldehydes, esters, ketones

•Weak: hydrocarbons, halocarbons, ethers

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SELECTIVITYInteraction Strengths

Phase Dipersion Dipole H Bonding

Methyl Strong None None

Phenyl Strong None Weak

Cyanopropyl Strong Strong Moderate

Trifluoropropyl Strong Moderate Weak

PEG Strong Strong Moderate

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COMPOUNDSProperties

Compounds Polar Aromatic HydrogenBonding Dipole

Toluene no yes no induced

Hexanol yes no yes yes

Phenol yes yes yes yes

Decane no no no no

Naphthalene no yes no induced

Dodecane no no no no

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50% CYANOPROPYL

0 2 4 6 8 10 12 14 16

100% Methyl

12

34

56

0 2 4 6 8 10 12 14 16

4 16 2

5 350%Cyanopropyl

1. Toluene2. Hexanol3. Phenol4. Decane (C10)5. Naphthalene6. Dodecane (C12)

Strong DispersionStrong DipoleModerate H Bonding

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Polysiloxanes(Methyl Substituted)

100 % methyl (HP-1, DB-1 etc.) Nonpolar

Si

Me

Me

O

n

% = # of sites on silicon atoms occupied

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Polysiloxanes(Phenyl methyl Substituted)

5% phenyl (HP-5, DB-5, etc.)35% phenyl (HP-35, DB-35, etc.)50% phenyl (HP-50+, DB-17, etc.)

NonpolarMid-polarMid-polar

Si

Me

Me

O

m

OSiO

Ph

Ph n

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Polysiloxanes(Cyanopropylphenyl methyl Substituted)

6% cyanopropylphenyl (HP-1301, DB-1301, etc.)14% cyanopropylphenyl (HP-1701, DB-1701etc.)50% cyanopropylphenyl (HP-225, DB-225, etc.)

Mid-polarMid-polarPolar

Si

Me

Me

O

n

OSiO

R

R' m

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HP-17: 50% phenyl and 50% methyl siloxanevs

HP-50+ : (50%)-Diphenyl (50%)-Dimethylpolysiloxane

CH3 n

Si O

3CH

CH3

m n

Si SiO O

Two columns are different !!

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Poly(ethylene) Glycol

100% PEG (HP-WAX)

Less stable than polysiloxanesUnique separation characteristics

Polar

HH

HO - - C-C-O- -H

H H n

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POLARITYSolubility And Retention

Same GC conditionsSame column dimensionsOnly differ in stationary phase

0 2 4 6 8

0 2 4 6 8

C10 C12

Hexanol 100% PEG(polar)

HexanolC10 C12

100% Methyl(non-polar)

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1. Stationary phase

3. Length(m)4. Film Thickness(um)

2. Inner Diameter(mm)

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COLUMN DIAMETERRetention

80°C isothermal

Isothermal: Retention is inversely proportional to column diameterTemperature program: 1/3-1/2 of isothermal values

0.25 mm

0 5 10 15 20

21.81

0.32 mm

0 2 4 6 8 10 12 14 16

16.06

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COLUMN DIAMETER(0.05~0.53mm)

0.32 mm0.53 mm

n =58,700 n =107,250

Sample capacity : < 2 ug < 500 ngInstrumental condition

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Phase RatioThe combined effect of the column diameter andfilm thickness is described by the phase ratio.

=

where

,

r = column radius ( m)df = film thickness ( m)

r/2d f

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Differing Column Inner Diameter, Equal Betas

Time (min)0 5 10 15 20

Carrier:Oven: 65°CInjection: SplitDetector: FID

ColumnA: HP-624

ColumnB: HP-624

HP part no. 19091V-41330 m, 0.32 mm, 1.8 m

Helium,40 (m/sec)

HP part no. 19095V-42330 m, 0.53 mm, 3 m

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1. Stationary phase2. Inner Diameter(mm)

4. Film Thickness(um)3. Length(m)

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COLUMN LENGTHTheoretical Efficiency

0.25 mm IDN/m = 4762 (for k = 5)

Length (m) N

15 71,430

30 142,860

60 285,720

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COLUMN LENGTH(10~120m)Resolution and Retention:

Isothermal

Double the plates, double the time but not double the the resolution

15 m 60 m30 m

R=0.842.29 min

R=1.68

8.73 min

R=1.16

4.82 min

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1. Stationary phase2. Inner Diameter(mm)3. Length(m)4. Film Thickness(um)

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FILM THICKNESS(0.1~5um)Retention: Isothermal

0 5 10 15 20 25

0 2 4 6 8

7.00

25.00

0.25 µm

1.00 µm

Thermal stabilitySample b.p.

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FILM THICKNESSBleed

More stationary phase = More degradation products

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+

Again

Si Si Si Si Si Si SiO O O O O O OH

CH3 CH3 CH3 CH3 CH3 CH3 CH3

CH3 CH3 CH3 CH3 CH3 CH3 CH3

OHSiSi O Si O Si O

CH3 CH3 CH3 CH3

CH3 CH3 CH3 CH3Si

O O

O

CH3H3C

H3C

H3C

SiSiCH3

CH3

OO O O O

OSi

HO

H3C

CH3 CH3 CH3 CH3

Si SiSi Si Si SiCH3

CH3

CH3

CH3CH3 CH3

CH3

CH3

CH3

“Back biting” Mechanism of Bleed Formation

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Phases tailored to “mimic” currently existing polymers

-Examples: DB-5ms, DB-35ms, DB-17msNew phases unrelated to any previously existing

polymers

-Example: DB-XLBOptimized manufacturing processes

-Example: DB-1ms

Four Types Of Low Bleed Phases

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Column Installation

1) Choosing ferrule2) Cutting the capillary column3) Inlet installation4) Leak-checking5) Outlet installation6) Establishing flow7) Conditioning

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Ferrule

• Graphite(100%) - 450℃ - general purpose and reused - FID, NPD, ECD - Not good for Mass

• Vespel(100%) - 280℃ - reused - for only isothermal operation

1) Choosing ferrule2) Cutting the capillary column3) Inlet installation4) Leak-checking5) Outlet installation6) Establishing flow7) Conditioning

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Cutting

• Jagged silica edges or exposed polyimide cause adsorption and tailing peaks, so it is very important that the column ends are cut uniformly.

1) Choosing ferrule2) Cutting the capillary column3) Inlet installation4) Leak-checking5) Outlet installation6) Establishing flow7) Conditioning

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Inlet installation

① 먼저 column nut 를 capillary column 에 끼우고 ferrule 을 끼운다 .

② 3cm 이상 capillary 가 나오게 한 후 먼저 inlet에 조여 capillary 가 ferrule 에 적당히 물리게 한다 .

③ 일단 푼다 .④ capillary 를 5mm 정도 남겨놓고 자른다 .⑤ 다시 inlet 에 연결한다 .⑥ 손으로 꽉 조인 상태에서 ¼~ 반바퀴 더 wrench

로 돌린다 . ⑦ 이동상을 흘렸을 때 이 부분에 Leak 가 있을

경우 injector 압력 gauge 가 올라가지 않는다 .

1) Choosing ferrule2) Cutting the capillary column3) Inlet installation4) Leak-checking5) Outlet installation6) Establishing flow7) Conditioning

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Leak-checking

Use acetone in vial

1) Choosing ferrule2) Cutting the capillary column3) Inlet installation4) Leak-checking5) Outlet installation6) Establishing flow7) Conditioning

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Outlet installation

• 보통 detector jet orifice 보다 1-3mm 아래쪽에 column end 가 있게 한다 ( 보통 capillary 를 detector 안쪽으로 끝까지 밀어 넣어 넣은 후 2mm 정도 뒤로 뺀다 ).

• column nut 와 ferrule 을 끼우는 요령은 inlet과 같다 .

1) Choosing ferrule2) Cutting the capillary column3) Inlet installation4) Leak-checking5) Outlet installation6) Establishing flow7) Conditioning

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Carrier gas Flow

1) Choosing ferrule2) Cutting the capillary column3) Inlet installation4) Leak-checking5) Outlet installation6) Establishing flow7) Conditioning

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Conditioning

• 40℃ start and 5~10℃/min• below 20~25℃

1) Choosing ferrule2) Cutting the capillary column3) Inlet installation4) Leak-checking5) Outlet installation6) Establishing flow7) Conditioning

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Storage

• septum on each end of the column

• Especially for PEG type column

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Split/Splitless Injection

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Splitless Injection

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And Now Let’s do Some

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DB-624 COLUMNQC Test Mix

Column: DB-624 30m x 53mm I.D., 3.0µm

Carrier: Helium at 40 cm/sec measured at 35°C

Injector: Mega Direct, 260°CDetector: FID, 300°COven: 35°C for 1.50 min 30°/min to 65° for 10 min

1. 1,2-Dichloropropane2. Octane3. Tetrachloroethylene4. Chlorobenzene5. Nonane

5 10 15 20 25

1.0e4

2.0e4

3.0e4

4.0e4

5.0e4

6.0e4

7.0e4

8.0e4

Time (min.)

2.71

7.4310.92

12.4917.42

20.78

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Example of Column Contamination

DB-624 QC Test Mix* After 75 Injections of Oily Sample

0 5 10 15 20

6000

7000

8000

9000

1.0e4

1.1e4

1.2e4

1.3e4

1.4e4

1.5e4

Time (min.)

2.21

3.30

6.03

9.26

10.46 14.40 17.86

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Column and Liner Contamination

Inlet coil of column

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Example of Column Contamination

Removed 1 1/2 m from injector end *

Time (min.)0 5 10 15 20 25

5000

6000

7000

8000

9000

1.0e4

1.1e4

1.2e4 2.80

7.34

10.79

12.33

17.19

20.56

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Backflush Column

1/16" flexible teflon line to regulated pressure source

Beaker for solvent collection

Capillary column

Special connectorand ferrule

Flexible teflontubing

Special adapter

CapVial

Capillary column

Rinse with 10ml each:Methanol, Methylene Chloride, Hexane

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Multiple cause and effect

Do not change too many variables at once

Complete system = Carrier Gas + Injector + Column + Detector + Data System

Remember