Chapter 7
Gas Chromatograph
7.1 Introduction to Interphase Separations
1,Interphase Separations
Mixed
Substances
Mobile Phase
Stationary Phase
Separated
Components
2,Classification of Chromatography
Instrumentation
By the types of mobile phase & stationary phase
Gas - Liquid GLC
Gas - Solid GSC
Liquid - Liquid LLC
Liquid - Solid LSC
By stationary’s forms
Column
Paper
thin layer
By separation mechanism
absorption
partition
exchange
3,Typical GCS Progresses
Carrier gas
Column
InjectorSample
Detector
Chromatogram
7.2 Principle of GC
1,The Interphase Partition of One Substance
C(m) C(s)
(1) Partition Coefficient K
m
s
C
CK?
7-1
(2) Partition Ratio k
p,q,mass fraction in the stationary and mobile phase
k,Partition Ratio or Capacity factor
m
s
q
pk?
1 ms mms s ww www wqp
k
V
V
q
p
Vq
Vp
C
CK
s
m
m
s
m
s
/
/
,phase ratio
7-2
7-3
7-4
2.Theoretical Plate
(1) Some common relationship
qkqppq qVc cVFt tFFFuA AuuuR mmmmms 1 1/1 1
(2) Theoretical Plate Model:
Height Equivalent to a Theoretical Plate(HETP)
Gas Flow rate is 1 plate Volume per time
K is a constant
Sample come into the plate only by the plate No,0
7-5
Binomial distributing
rrnr
nrn
n
r
rn
n
qpcf
fqp
,
1
,
7-7
7-6
rn
s
rn
rn
m
rn
pfW
qfW
,,
,,
3,Export Curve Equation
(1) Export Curve Equation
(Gauss distribution)
e
Rttc
c 2
2
20
2
7-8
(2) The Shape of Export curve
tm (tair),unreteined time
tR,retention time
T’R,adjusted retention time
Vm (Vair),unreteined volume
VR,retention volume
V’R,adjusted retention volume
h,Peak of zone?,Standard deviation
Y,Width of zone Y1/2,Half peak width
mRR ttt
'
36.22ln222/1Y
4?Y
m
R
t
tk '?
)1( ktt mR
7-9
7-10
7-11
7-12
7-13
(3) The Number of theoretical plate and HETP
22
2/1
1654.5?
Y
t
Y
tn RR
22
2/1
'16'54.5?
Y
t
Y
tn RR
e f f e c t
e ffe c t
e ffe c t n
LH?
e ffe c tnk
kn 1
L,length of the column
7-14
7-15
7-15
7-17
4.Van Deemter Equation
u,velocity of the
carrier gas
A,B and C are the
constants for a
given system
cu
u
BAH 7-18
7.3 Separation of Components
1,Separation for tow components
(1)Resolution R
)21
1,2,
(5.0 YY
ttR RR
(2)Separation Factor
1
2
1
2
1
2
1
2
'
'
'
'
V
V
t
t
k
k
K
K
7-19
7-20
2,Separation Equation of GC
Assume,Y1=Y2=Y,k1≈k2=k
2121216 kkRn
21216Rn e f f e c t
141 e f f e c tnR
7-21
7-22
7-23
3,Three Separation factor
(1) Column effect factor n
(2) Capacity factor k
(3) Selective factor?
4,The Choice of experimental qualification
(1) Flow rate of carrier gas
cuuBAH
uuBdudH 2
CBb e s tu?
BCAH 2m i n
7-24
7-25
7-26
7-27
(2) Column temperature
low mid high
100～ 200℃ 200 ～ 300 ℃ 300 ～ 400 ℃
(3) Column types
Stationary type
Stationary Liquid and Temperature
Supporter
(4) Injection time and volume
7.4 GC Instrument
1,Gas Supply
Type Function
Hydrogen Carrier,Fuel gas
Nitrogen Carrier
Helium Carrier
Argon Carrier
2,Sample Injector
3,Column System
(1)Capillary GC Columns
(2) stationary phases
Polysiloxanes
4,Detector
(1) Two Kinds of Detectors
Thermal conductivity detector (TCD)
While equilibrium,
R1R3=R2R4
Electron capture detector (ECD)
Flame ionization detector (FID)
Flame photometric detector (FPD)
(2) Behavior of Detector
Sensitivity
CSR c?
a) for concentration types
Q
RS
0
AmFkS c?
7-28
7-29
7-30
b) For mass types
dt
dmSR
m?
AmkS m 1?
Detect limit
S
ND 2?
N,noise of detector(mV) A,area of the signal
7-31
7-32
7-33
Minimum detect quantity Q0
Response time
Linear response range
DYA 2/10 6 5.1?For mass:
For concentration:
DYQ 2/10 065.1?
FDYQ 2/10 0 6 5.1?
7-34
7-35
7-36
7.5 Qualitative analysis
1,Comparison with pure maters
2,Work as a part of analysis system
GC-IR GC-MS
3,Retention Index
7.6 Quantitative analysis
1,Quantitative Equation
For same detector,different substance have
different response sensitivity,
iii Afm?
Is called as Quantitative correction factor
if
The equation Is Quantitative Equation.
j
jj
iA
j
j
i
T
i
i Af
f
m
m
m
m
m i%
7-37
7-38
2,Determination of zone area
(1) By calculation
2/1hYA?
2/10 6 5.1 hYA?
hYA?
RhtA?
(2) Numerical integral by computer
(3) By instrumental integral
3,Normalization Methods
Assume the zones of every substance mj
in sample have obtained,so:
%1 0 0
%1 0 0 %1 0 0%
j
jj
ii
j
j
i
T
i
i
fA
fA
m
m
m
m
C
%100%
i
iC
7-39
4,Internal standard Methods
Use a internal standard sample its mass is a
constant known as ms and its zone area is As
s
ss
ii
i mAf
Afm?
s
i
s
i
s
si
s
ss
iii
i
A
A
K
A
A
mf
mf
m
m
Af
Af
m
m
C
%1 0 0
%1 0 0%1 0 0% 7-40
7-41
Gas Chromatograph
7.1 Introduction to Interphase Separations
1,Interphase Separations
Mixed
Substances
Mobile Phase
Stationary Phase
Separated
Components
2,Classification of Chromatography
Instrumentation
By the types of mobile phase & stationary phase
Gas - Liquid GLC
Gas - Solid GSC
Liquid - Liquid LLC
Liquid - Solid LSC
By stationary’s forms
Column
Paper
thin layer
By separation mechanism
absorption
partition
exchange
3,Typical GCS Progresses
Carrier gas
Column
InjectorSample
Detector
Chromatogram
7.2 Principle of GC
1,The Interphase Partition of One Substance
C(m) C(s)
(1) Partition Coefficient K
m
s
C
CK?
7-1
(2) Partition Ratio k
p,q,mass fraction in the stationary and mobile phase
k,Partition Ratio or Capacity factor
m
s
q
pk?
1 ms mms s ww www wqp
k
V
V
q
p
Vq
Vp
C
CK
s
m
m
s
m
s
/
/
,phase ratio
7-2
7-3
7-4
2.Theoretical Plate
(1) Some common relationship
qkqppq qVc cVFt tFFFuA AuuuR mmmmms 1 1/1 1
(2) Theoretical Plate Model:
Height Equivalent to a Theoretical Plate(HETP)
Gas Flow rate is 1 plate Volume per time
K is a constant
Sample come into the plate only by the plate No,0
7-5
Binomial distributing
rrnr
nrn
n
r
rn
n
qpcf
fqp
,
1
,
7-7
7-6
rn
s
rn
rn
m
rn
pfW
qfW
,,
,,
3,Export Curve Equation
(1) Export Curve Equation
(Gauss distribution)
e
Rttc
c 2
2
20
2
7-8
(2) The Shape of Export curve
tm (tair),unreteined time
tR,retention time
T’R,adjusted retention time
Vm (Vair),unreteined volume
VR,retention volume
V’R,adjusted retention volume
h,Peak of zone?,Standard deviation
Y,Width of zone Y1/2,Half peak width
mRR ttt
'
36.22ln222/1Y
4?Y
m
R
t
tk '?
)1( ktt mR
7-9
7-10
7-11
7-12
7-13
(3) The Number of theoretical plate and HETP
22
2/1
1654.5?
Y
t
Y
tn RR
22
2/1
'16'54.5?
Y
t
Y
tn RR
e f f e c t
e ffe c t
e ffe c t n
LH?
e ffe c tnk
kn 1
L,length of the column
7-14
7-15
7-15
7-17
4.Van Deemter Equation
u,velocity of the
carrier gas
A,B and C are the
constants for a
given system
cu
u
BAH 7-18
7.3 Separation of Components
1,Separation for tow components
(1)Resolution R
)21
1,2,
(5.0 YY
ttR RR
(2)Separation Factor
1
2
1
2
1
2
1
2
'
'
'
'
V
V
t
t
k
k
K
K
7-19
7-20
2,Separation Equation of GC
Assume,Y1=Y2=Y,k1≈k2=k
2121216 kkRn
21216Rn e f f e c t
141 e f f e c tnR
7-21
7-22
7-23
3,Three Separation factor
(1) Column effect factor n
(2) Capacity factor k
(3) Selective factor?
4,The Choice of experimental qualification
(1) Flow rate of carrier gas
cuuBAH
uuBdudH 2
CBb e s tu?
BCAH 2m i n
7-24
7-25
7-26
7-27
(2) Column temperature
low mid high
100～ 200℃ 200 ～ 300 ℃ 300 ～ 400 ℃
(3) Column types
Stationary type
Stationary Liquid and Temperature
Supporter
(4) Injection time and volume
7.4 GC Instrument
1,Gas Supply
Type Function
Hydrogen Carrier,Fuel gas
Nitrogen Carrier
Helium Carrier
Argon Carrier
2,Sample Injector
3,Column System
(1)Capillary GC Columns
(2) stationary phases
Polysiloxanes
4,Detector
(1) Two Kinds of Detectors
Thermal conductivity detector (TCD)
While equilibrium,
R1R3=R2R4
Electron capture detector (ECD)
Flame ionization detector (FID)
Flame photometric detector (FPD)
(2) Behavior of Detector
Sensitivity
CSR c?
a) for concentration types
Q
RS
0
AmFkS c?
7-28
7-29
7-30
b) For mass types
dt
dmSR
m?
AmkS m 1?
Detect limit
S
ND 2?
N,noise of detector(mV) A,area of the signal
7-31
7-32
7-33
Minimum detect quantity Q0
Response time
Linear response range
DYA 2/10 6 5.1?For mass:
For concentration:
DYQ 2/10 065.1?
FDYQ 2/10 0 6 5.1?
7-34
7-35
7-36
7.5 Qualitative analysis
1,Comparison with pure maters
2,Work as a part of analysis system
GC-IR GC-MS
3,Retention Index
7.6 Quantitative analysis
1,Quantitative Equation
For same detector,different substance have
different response sensitivity,
iii Afm?
Is called as Quantitative correction factor
if
The equation Is Quantitative Equation.
j
jj
iA
j
j
i
T
i
i Af
f
m
m
m
m
m i%
7-37
7-38
2,Determination of zone area
(1) By calculation
2/1hYA?
2/10 6 5.1 hYA?
hYA?
RhtA?
(2) Numerical integral by computer
(3) By instrumental integral
3,Normalization Methods
Assume the zones of every substance mj
in sample have obtained,so:
%1 0 0
%1 0 0 %1 0 0%
j
jj
ii
j
j
i
T
i
i
fA
fA
m
m
m
m
C
%100%
i
iC
7-39
4,Internal standard Methods
Use a internal standard sample its mass is a
constant known as ms and its zone area is As
s
ss
ii
i mAf
Afm?
s
i
s
i
s
si
s
ss
iii
i
A
A
K
A
A
mf
mf
m
m
Af
Af
m
m
C
%1 0 0
%1 0 0%1 0 0% 7-40
7-41
