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Alternate Carrier Gas Considerations and
Faster GC Analysis
Page 1
Faster GC Total Analytical Cycle Times
– A Variety of Approaches
Post-Run
Bake-Out
Chromatographic
Run
Post-Run
Cool-Down
Pre-Run
ALS Set-Up
Included “ALS Sample Overlap” 7890 GC
in in ChemStation SW Faster Cool-down
HW/SW
Column & Gas Selection,
Method Translation
New Devices Capillary Flow Technology
Signficantly Faster GC (Backflush)
Analytical Cycle Times
LTM Technology LTM Technology
(Rapid Heating) (Rapid Cooling )
Page 2
Page 3
•Stationary Phase
•Carrier Gas: type and linear velocity
•Shorten Column Length
•Decrease Internal Diameter
•Temperature Programming
Variables for Shortening GC Run Times
Carrier Gas
Affects resolution and retention time
Optimal range of velocities
Too low or high results in loss of resolution
Page 4
van Deemter Curve
10 20 30 40 50 60
0.25
0.50
0.75
1.00
u (cm/sec)
h
ū opt OPGV
Excessive Diffusion
Poor Mass Transfer
Page 5
•ūopt = Maximum efficiency (ūmin)
•OPGV = Optimal Practical Gas Velocity Maximum efficiency per unit time (1.5 – 2 x ūopt )
Nitrogen = 0.15 cm2/sec
Helium = 0.4 cm2/sec
Hydrogen = 0.6 cm2/sec
© Walter Jennings, 1999
Diffusion Constants for Dodecane @ 150oc
Page 6
Gas Viscosity vs Temperature
J.V. Hinshaw, Column Connections, LCGC Asia Pacific, 12(2), 1100 (2009).
Page 7
10 20 30 40 50 60
0.25
0.50
0.75
1.00
u (cm/sec)
h
12-20 cm/sec
N 2
van Deemter Curve Nitrogen
Page 8
10 20 30 40 50 60
0.25
0.50
0.75
1.00
u (cm/sec)
h
He
28-40cm/sec
van Deemter Curve Helium
Page 9
10 20 30 40 50 60
0.25
0.50
0.75
1.00
u (cm/sec)
h H 2
38-60 cm/sec
van Deemter Curve Hydrogen
Page 10
Carrier Gas - Hydrogen Comments
Hydrogen is extremely diffusive in air
Difficult to reach explosive level of ~4 %
Most GC's flow regulated with safety shutdown
Spring loaded/Explosion ready doors
Page 11
Hydrogen as Carrier – Contamination?
Contamination of GC flow modules and lines. Hydrogen acts as a scrubber. On the MS this typically looks like Hydrocarbon contamination Most people report that it takes 2-4 weeks to clean out, depending on flows. The FID only sees a high background for that time. Other issues? H2 + Cl Solvent + Heat = HCl?
Page 12
Contamination?! – scrubbing, vapor volume or HCl
Page 13
Methylene Chloride + Hydrogen carrier
(don’t see this with Helium carrier)
Hydrogen as Carrier – MS and Lower Pressures
Hydrogen is more difficult for the MS vacuum system to pump away as compared to Helium. Be careful not to get to a “negative” head pressure situation. (pulling instead of pushing flow is not good). Trace level work on the MS requires low flow rates. Must use smaller ID columns so you don’t have higher flow rates. (length plays a role as well) 0.18mm ID or smaller is ideal for trace level MS work when using Hydrogen.
Page 14
The Only GC-MS Engineered for Hydrogen Carrier
Gas to Reduce Operating Costs
NEW Presentation!
“Conversion of Agilent
EI GC/MSD Systems To
Hydrogen Carrier Gas” (make a note on your
evaluation sheet to send)
http://www.chem.agilent.com
/en-US/Promotions/pages/
alternate-carrier-gas.aspx
Page 15
Page 16
Programmable Helium Conservation Module
Page 17
Programmable Helium Conservation Module
He to N2 Conversion (E-Max, Diesel)
Page 18
Nitrogen
Helium
“Good Enough” Gas Chromatography
Page 19
Column Dimensions
Diameter
Length
Page 20
The Secrets Are In There
N = (gas, L, rc)
k = (T, df, rc)
a = (T, phase)
RN k
ks =
4 1
1
a
a
Efficiency
Retention
Selectivity
L = Length
rc = column radius
df = film thickness
T = temperature
Page 21
Column Diameter - Theoretical Efficiency
I.D. (mm) n/m
0.05 23,160
0.10 11,980
0.20 5830
0.25 4630
0.32 3760
0.45 2840
0.53 2060
0.18 6,660
k = 5
Page 22
Combining a change in Length
with a change in Diameter E
ffic
iency
Analysis Time
Decrease Length
Decrease Diameter
Page 23
Column Diameter and Capacity
Like Polarity
Phase/Solute
0.25 µm film thickness
I.D. (mm) Capacity (ng)
0.05 1-2
0.18 25-55
0.20 35-70
0.25 80-160
0.32 110-220
0.53 1000-2000
0.45 600-800
0.10 6-13
Page 24
Changes in Column Dimensions, Gas Type or
Velocity Require Changes in Temp Program Rates
Method Translation Software to the Rescue!
Page 25
To Get the Software:
http://www.chem.agilent.com/en-US/Technical-
Support/Instruments-Systems/Gas-
Chromatography/Pages/gcmethodtranslation.aspx
OR
Google Agilent GC Method Translation Software
Page 26
2 . 0 0 4 . 0 0 6 . 0 0 8 . 0 0 1 0 . 0 0 1 2 . 0 0 1 4 . 0 0 1 6 . 0 0 1 8 . 0 0
1 e + 0 7
2 e + 0 7
3 e + 0 7
4 e + 0 7
5 e + 0 7
6 e + 0 7
7 e + 0 7
8 e + 0 7
9 e + 0 7
1 e + 0 8
1 . 1 e + 0 8
1 . 2 e + 0 8
1 . 3 e + 0 8
1 . 4 e + 0 8
1 . 5 e + 0 8
1 . 6 e + 0 8
1 . 7 e + 0 8
1 . 8 e + 0 8
1 . 9 e + 0 8
T im e
R e s p o n s e _
G C 3 -6 7 0 7 . D \ E C D 2 B
22
21
20
19
18
17
16
15 14
13
12
11
10
9
8
7
5,6
4
3
2
1
Column: DB-XLB
30m x 0.32mm i.d., 0.25µm
Carrier: He, constant flow, 38 cm/s at 120°C
Injector: Pulsed Splittless, 220 °C
Pulse pressure & time: 35psi for 1.15min
2µL, 50ppb
Oven: 120°C for 1.17min
120°C to 160°C at 25°/min
160°C to 260°C at 10°/min
260°C to 300°C (4min) at 15°/min
Detector: µ-ECD, 320°C
Ar/CH4 (P5) makeup gas at 60mL/min
<16 minutes
CLP-Pesticides - Original “Improved” Method
0.32mm I.D., Helium Carrier Gas
Page 27
Input Original Method Parameters
Page 28
New Velocity
New Temp.
Program
New Column Dimensions, H2 Gas, Fast Analysis
Input NEW
dimensions
Close enough
(got lucky)
Page 29
0 . 5 0 1 . 0 0 1 . 5 0 2 . 0 0 2 . 5 0 3 . 0 0 3 . 5 0 4 . 0 0 4 . 5 0 5 . 0 0 5 . 5 0 6 . 0 0 6 . 5 0 7 . 0 0
2 0 0 0 0 0 0
4 0 0 0 0 0 0
6 0 0 0 0 0 0
8 0 0 0 0 0 0
1 e + 0 7
1 . 2 e + 0 7
1 . 4 e + 0 7
1 . 6 e + 0 7
1 . 8 e + 0 7
2 e + 0 7
2 . 2 e + 0 7
2 . 4 e + 0 7
2 . 6 e + 0 7
2 . 8 e + 0 7
3 e + 0 7
3 . 2 e + 0 7
3 . 4 e + 0 7
3 . 6 e + 0 7
T i m e
R e s p o n s e _
G C 8 - 3 3 6 7 . D \ E C D 2 B
22
21
20
19
18
17
16
15 14
13
12
11
10 9
8
7
6
5
4
3
2
1
Column: DB-XLB
20m x 0.18mm i.d., 0.18µm
Carrier: H2, constant flow, 77.3cm/s at 120°C
Injector: Pulsed Splittless, 220 °C
Pulse pressure & time: 35psi for 0.5min
Flow ramp at 6.25min of 99mL/min2 to 3mL/min
2mm i.d. liner
0.5µL, 50ppb
Oven: 120°C for 0.49min
120°C to 160°C at 59.4°/min
160°C to 260°C at 23.7°/min
260°C to 300°C (1.69min) at 35.6°/min
Detector: µ-ECD, 320°C
Ar/CH4 (P5) makeup gas at 60mL/min
Final Method Used at EPA
Page 30
0 . 5 0 1 . 0 0 1 . 5 0 2 . 0 0 2 . 5 0 3 . 0 0 3 . 5 0 4 . 0 0 4 . 5 0 5 . 0 0 5 . 5 0 6 . 0 0 6 . 5 0 7 . 0 0
2 0 0 0 0 0 0
4 0 0 0 0 0 0
6 0 0 0 0 0 0
8 0 0 0 0 0 0
1 e + 0 7
1 . 2 e + 0 7
1 . 4 e + 0 7
1 . 6 e + 0 7
1 . 8 e + 0 7
2 e + 0 7
2 . 2 e + 0 7
2 . 4 e + 0 7
2 . 6 e + 0 7
2 . 8 e + 0 7
3 e + 0 7
3 . 2 e + 0 7
3 . 4 e + 0 7
3 . 6 e + 0 7
T i m e
R e s p o n s e _
G C 8 - 3 3 6 7 . D \ E C D 2 B
DB-XLB
0 . 5 0 1 . 0 0 1 . 5 0 2 . 0 0 2 . 5 0 3 . 0 0 3 . 5 0 4 . 0 0 4 . 5 0 5 . 0 0 5 . 5 0 6 . 0 0 6 . 5 0 7 . 0 0
2 0 0 0 0 0 0
4 0 0 0 0 0 0
6 0 0 0 0 0 0
8 0 0 0 0 0 0
1 e + 0 7
1 . 2 e + 0 7
1 . 4 e + 0 7
1 . 6 e + 0 7
1 . 8 e + 0 7
2 e + 0 7
2 . 2 e + 0 7
2 . 4 e + 0 7
2 . 6 e + 0 7
2 . 8 e + 0 7
3 e + 0 7
3 . 2 e + 0 7
3 . 4 e + 0 7
3 . 6 e + 0 7
T i m e
R e s p o n s e _
G C 8 - 3 3 6 7 . D \ E C D 1 A
V i e w M o d e : I n t e g r a t i o n
DB-17ms
22
21
20
19
18
17
16 15 14
13
12
11
10 9 8
7
6
5
4
3
2
1
22
21
20
19
18 17
16 15
14
13 12
11
10 9 8
7
6
5
4
3 2
1
Final Method Used at EPA
Page 31
Cumene Analysis
-60m x 0.32mm ID (overkill)
min0 5 10 15 20 25 30
pA
5
6
7
8
9
10
FID1 B, (STANDARD\SIG22847.D)
4.5
70
5.3
41
5.7
31
6.5
25
8.6
88
8.9
87
11.9
46
12.5
72
13.1
00
13.7
07
14.4
95
15.5
44
16.1
45
16.3
40
17.1
18
17.6
73
18.2
57
19.2
53
26.3
50
30.3
40
Page 32
Cumene Analysis
-30m x 0.25mm ID
min0 1 2 3 4 5 6 7
pA
5
6
7
8
9
10
11
12
13
FID1 B, (STANDARD\SIG22988.D) 0
.749
0.8
30
1.1
23
1.2
43
1.6
49
2.6
18
3.7
00
3.8
35
4.1
00
4.1
35
4.2
58
4.4
64
4.5
93
4.6
23
4.7
85
4.9
81
5.0
90
5.3
02
5.9
37
6.0
92
6.5
49
Page 33
Cumene Analysis
-20m x 0.18mm ID
min0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
pA
4
5
6
7
8
9
FID1 A, (MISC\SIG15011.D)
0.8
72
0.9
67
1.3
03
1.4
29
1.8
01
2.4
33
3.0
72
3.1
48
3.2
54
3.2
98
3.3
62
3.4
63
3.5
18
3.5
34
3.6
11
3.6
99
3.7
60
3.8
43
4.1
41
4.2
31
Page 34
Cumene Analysis
-20m x 0.18mm ID, Hydrogen Carrier
min0 0.5 1 1.5 2 2.5 3 3.5 4
pA
4
5
6
7
8
9
FID1 A, (MISC\SIG15022.D)
0.5
39
0.5
97
0.8
03
0.8
88
1.1
80
1.7
76
2.4
08
2.4
86
2.6
36
2.6
59
2.7
31
2.8
50
2.9
24
2.9
42
3.0
36
3.1
49
3.2
23
3.3
31
3.6
87 3
.785
Page 35
Food/Fragrance – Method translation
Page 36
Spearmint Oil on DB-1
Δ -9.7 min 0.18 mm, He Carrier
17.7 min
3 8 13 18 23 28
0.25 mm, He Carrier
Time (min)
27.4 min
Page 37
Food/Fragrance – Method translation, Hydrogen
Page 38
Spearmint Oil on DB-1, (App. Note 5989-7509EN)
Δ -9.7 min 0.18 mm, He Carrier
Δ -16.8 min 0.18 mm, H2 Carrier
10.6 min
17.7 min
3 8 13 18 23 28
0.25 mm, He Carrier
Time (min)
27.4 min
Page 39
10.6 min
17.7 min
3 8 13 18 23 28
27.4 min
(0.25 mm, He Carrier)
Δ -9.7 min (0.18 mm, He carrier)
Δ -16.8 min (0.18 mm, H2 Carrier)
Spearmint Oil on DB-1 – Resolution Check
Page 40
Faster GC Total Analytical Cycle Times
– A Variety of Approaches
Post-Run
Bake-Out
Chromatographic
Run
Post-Run
Cool-Down
Pre-Run
ALS Set-Up
Included “ALS Sample Overlap” 7890 GC
in in ChemStation SW Faster Cool-down
HW/SW
Column & Gas Selection,
Method Translation
New Devices Capillary Flow Technology
Signficantly Faster GC (Backflush)
Analytical Cycle Times
LTM Technology LTM Technology
(Rapid Heating) (Rapid Cooling )
Page 41
New Devices for Faster Analyses
Low Thermal Mass Technology Capillary Flow Technology
Page 42
Purged Capillary Flow Devices
2-Way Splitter
with Makeup
3-Way Splitter
with Makeup Deans Switch
Page 43
Purged Union
(most recent)
All Purged Capillary Flow Devices are Capable of Backflushing
Backflush with Purged Union or Any Purged
Capillary Flow Technology Device
1 psi
80 psi
During GC Run
After GC Run
Inlet
Purged CFT
Device Column
25 psi
4 psi
MSD
Aux EPC Split Vent Trap
Inlet
Purged CFT
Device Column
MSD
Aux EPC Split Vent Trap
performance turbo
recommended
Page 44
5 10 15 20 25 30 35 40 45 50 55 60 65 70
Run stopped at 42 min and
backflushed at 280oC for 7 mins.
It took additional 33 mins
and column to 320oC to
remove these high boilers.
Blank run after backflushing
min
showing the column was clean.
Milk Extract
Page 45
Without Backflush: A Serious Problem
Overlay of two chromatograms of a blank extract injected BEFORE (A) and AFTER (B) three injections without backflush
Abundance
4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 0
2000000
4000000 6000000
8000000 1e+07
1.2e+07 1.4e+07
1.6e+07 1.8e+07 2e+07
2.2e+07 2.4e+07
2.6e+07 2.8e+07
3e+07 3.2e+07
3.4e+07 3.6e+07
3.8e+07 4e+07
4.2e+07 4.4e+07
4.6e+07
Time
A: TIC: lettuce_blank.D\data.ms
B: TIC: lettuce_blank3.D\data.ms
B
A
Data provided by MSD
user in Almeria, Spain
After only 3 10-µL
injections, the background
is significantly higher
(increase chemical noise is
every spectrum)
Page 46
With Backflush: No Increased Background (Less Spectral
Noise) and Consistent Retention Times
Stable retention times
and baseline . . . less
chemical noise
4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 0
2000000
4000000
6000000
8000000
1e+07
1.2e+07
1.4e+07
1.6e+07
1.8e+07
2e+07
2.2e+07
2.4e+07
2.6e+07
2.8e+07
3e+07
3.2e+07
3.4e+07
3.6e+07
3.8e+07
4e+07
4.2e+07
4.4e+07
4.6e+07
Time
Abundance
TIC: lettuce_10_ppb.D\data.ms
TIC: lettuce_100_ppb.D\data.ms
TIC: lettuce_5_ppb.D\data.ms
Overlay of three chromatograms of lettuce extract run with 2 min of back flush
Data provided by user
in Almeria, Spain
Page 47
Post-Column Backflush
Injector Detector
Transfer Line
Purged Ultimate Union
Column
Page 48
Mid-Column Backflush
Injector Detector
Purged Ultimate Union
Back Half Front Half
Column
Page 49
Pre-Column Backflush
Injector Detector
Pre-Column
Purged Ultimate Union
Column
Page 50
“LTM” (Low Thermal Mass) Technology (Patented)
Directly heat/cool fused silica GC columns
Page 51
Interfacing LTM GC to an Agilent 7890 or 6890 GC
GC oven door replaced with LTM-ready GC oven door (easy)
Use same GC injectors, detectors, autosamplers, software, …
Column Modules mount outside isothermal GC oven for fast
heating and cooling
Independent and simultaneous
temperature programming of
1-4 column modules
Note: Front thermal shield removed to show LTM column modules
Entire thermal shield should always be in place during operation
LTM Column Modules
LTM Control System
w/ Keypad User Interface
(LTM Control SW for ChemStation
Available from Agilent Nov/Dec’08)
Page 52
A Closer Look
LTM Column Module
LTM Column Assembly
LTM Retrofit Door
Page 53
Inside View
Page 54
LTM Heating Speeds
Heating speeds can be set up to
1800oC/min
- achievable rates depend on column
mass, configuration and column
void times
- … also including practical trade-offs
of speed vs resolution
Page 55
240V
120
95
65
45
35
120V
Insert
120
95
65
45
35
“Fast”
120V
75
45
40
30
20
“Standard”
Temp. Range (oC)
50 to 70
70 to 115
115 to 175
175 to 300
300 to 450
240V
Insert
120
120
110
80
65
“Turbo”
6890/7890 Oven Ramp Rates
Page 56
(oC/min)
Oven Insert For The 6890/7890
The insert reduces the 6890/7890
effective oven volume by 50%.
Allows 120V 6890/7890 to achieve ramp
rate equal to the 240V.
Allows faster oven cool down over std
6890.
Part No. G2646-60500
(Can’t use on 6890/ 5973 MS)
Page 57
Typical Cooling Times for a LTM Column (Standard Size)
oC 2 m 5 m 10 m 15 m 30 m
350->300 3 5 6 7 9
300->250 3 5 7 7 13
250->200 4 7 8 10 17
200->150 4 8 11 13 22
150->100 7 13 17 19 36
100->50 13 27 34 41 75
Column Length
Type Time
350oC 50oC LTM (2m Column) 34 seconds (= 3+3+4+4+7+13)
Equilibration 3 seconds
350oC 50oC 7890 GC 3-4 minutes
Equilibration 2-3 minutes
Page 58
Some Practical Uses of LTM Rapid Heating/Cooling
Environmental
Need for high through-put, especially for low margin samples
(eg. Total Petroleum Hydrocarbon (TPH)), where analytical cycle
times are a critical element in making a profit
Hydrocarbon Processing
Certain process control analyses (eg. Simulated Distillation) lend
themselves to batch analysis. Shorter analytical cycle times get
data back to operations faster, or allow more samples/shift
Page 59
TPH Analysis with Faster GC Run Times
(C10C44 Standard Shown)
Shorter Column,
2x Faster
Ramp Rate
min 5 10 15 20 25 30 35
pA
0 20
40
60
80
100
n-C
10
n-C
12 n
-C14
n-C
16
n-C
18
n-C
20
n-C
22
n-C
23
n-C
24
n-C
26
n-C
28
n-C
30
n-C
32
n-C
36
n-C
40
n-C
44
min 2 4 6 8 10 12 14 16 18 20
pA
20
40
60
80
100
120
n-C
10
n-C
12
n-C
14
n-C
16
n-C
18
n-C
20
n-C
22 n
-C23
n-C
24
n-C
26
n-C
28
n-C
30
n-C
32
n-C
36
n-C
40
n-C
44
min 0.5 1 1.5 2 2.5 3
pA
0
200
400
600
800
1000
n-C
10
n-C
12
n-C
14
n
-C16
n-C
18
n-C
20
n-C
22
n-C
23
n-C
24
n-C
26
n-C
28
n-C
30
n-C
32
n-C
36
n-C
40
n-C
44
10oC/min
30m Column - 7890
20oC/min
15m Column - 7890
200oC/min
5m Column –
LTM/7890 5m Column,
10x Faster
Ramp Rate
with LTM
Standard
GC Run Time
Page 60
LTM Also Greatly Reduces Cool-Down Times,
9x Faster Heating/Cooling Cycle Times
40 min + 5.4 min
20 min + 5.4 min
3 min + 2 min
GC Run Time Cool Down
9x Faster
Cycle Time
LTM/7890
Page 61
Page 62
CONCLUSIONS
Carrier Gas – Helium can still go fast but Hydrogen has the
most advantage at high velocities, Nitrogen might work (GEC)
Diameter – Smaller allows shorter length but has less capacity
Small Change in ID Easier to Translate – Again think capacity
Length – Shorter might be possible without losing a lot of R
Temperature Program – Use MTS to scale temps properly
Method Translation Software – FREE, reliable
Capillary Flow Technology – Backflush instead of Bake Out
Low Thermal Mass GC – Fast Heating, Fast Cooling
