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GC Resolution – Do You See What I See? Deans Switch Page 1 Column Dimensions and Carrier Gas Optimization
GC Resolution – Do You See What I See?
Deans Switch
Page 1
Column Dimensions and
Carrier Gas Optimization
Page 2
•Optimized Stationary Phase
•Longer Column Length
•Decrease Internal Diameter
•Carrier Gas: type and linear velocity
•Optimized Temperature Programming
Variables for Maximizing Resolution
Resolution
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 3
Agilent J&W has over 50 different stationary phase offerings
WCOT Column Types
Page 4
FactorFourTM Phases
VF-1ms, VF-5ms, VF-5ht, VF-5ht UltiMetal™
VF-17ms, VF-17ms for PAH, VF-35ms,
VF-200ms,VF-Xms, VF-23ms, VF-624ms,
VF-DA, VF-1301ms, VF-Pesticides,
VF-1701ms, VF-WAXms
Page 5
Column Typical Application
DB-624 EPA and USP volatiles
DB-VRX volatiles analysis
HP-VOC volatiles analysis
DB-502.2 EPA Method 502.2
DB-5.625 EPA semi-volatiles analysis
DB-608 EPA Method 608
DB-1701P EPA pesticides analysis
DB-MTBE total petroleum hydrocarbon (TPH)
HP-PONA petroleum hydrocarbon analysis
DB-HT SimDis hi-temp simulated distillation
DB-ALC1 & ALC2 blood alcohol analysis
HP-88 fatty acid methyl ester (FAME)
“Specialty phases” are columns that are optimized to perform
a specialized GC analysis.
20+ Different “Specialty Phases”
Page 6
Select TM Column Examples
Environmental applications
CP-Sil 88 for dioxins, Select mineral oil, CP-Select 624 CB
Chiral applications
CP-Chirasil Val, CP-Chirasil-DEX CB
Chemical applications
CP-Volamine, CP-Select CB for MTBE, CP-PONA C8, CP-Propox,
Select Silanes, CP-SimDist UltiMetal TM , CP-Lowox TM
Food and Beverage applications
CB-Carbowax 400, Select FAME, CP-Sil 88 for FAME, CP-FFAP CB
Page 7
PLOT columns are primarily, but not exclusively, used for the analysis of gases and low boiling
point solutes (i.e., boiling point of solute is at or below room temperature).
PLOT Column Types
• Agilent J&W PLOT columns begin
with the designation of
– GS (Gas Solid) or
– HP-PLOT followed by a specific name
– 10 stationary phases
• GS-OxyPLOT
• GS-Alumina
• HP-PLOT Al2O3 “M”
• HP-PLOT Al2O3 “S”
• HP-PLOT Al2O3 “KCl”
• HP-PLOT MoleSieve
• GS-CarbonPLOT
• HP-PLOT Q
• HP-PLOT U
• GS-GasPro
• GS-OxyPLOT: oxygenates
• HP-PLOT Molesieve: O2, N2, CO, Methane
• HP-PLOT Alumina and GS-Alumina: complex hydrocarbon gas matrices, ethylene and
propylene purity, 1,4-butadiene
• HP-PLOT Q: freons, sulfides
• HP-PLOT U: C1 to C7 hydrocarbons, CO2, Polar Hydrocarbons
• GS-GasPro: freons, sulfurs, inorganic gases
• GS-CarbonPLOT: inorganic and organic gases
Page 8
PLOT GC Columns from Varian Line
Porous Polymers
• CP-PoraBOND Q
• CP-PoraBOND U
• CP-PoraPLOT Q
• CP-PoraPLOT U
• CP-PoraPLOT S
• CP-PoraPLOT Q-HT
• CP-PoraPLOT amines
Zeolites
• Molsieve 5A
• Molsieve 13x
Alumina
• KCL
• Na2SO4
• MAPD
Multi Layer
• CP-Lowox
Porous Silica
• SilicaPLOT
Graphatised Carbon
• CP-CarboPLOT P7
• CP-CarboBOND
SelectTM permanent gases
Page 9
Page 10
Optimizing Selectivity
Match analyte polarity to stationary phase polarity
-like dissolves like (oil and water don’t mix)
Take advantage of unique interactions between analyte and
stationary phase functional groups
Page 11
Stationary Phase Selection
Existing Information
Critical Separations
Selectivity/Polarity
Temperature Limits
Application Designed
Examples: DB-CLP1, DB-CLP2, DB-UI 8270D, DB-624UI,
DB-Select 624UI<467>, DB-VRX, HP-VOC, DB-MTBE,
Lowox, DB-TPH, DB-HTSimDis, DB-2887, DB-HT SimDis,
CP-Volamines, DB-ALC1, DB-ALC2, Select Phases, etc.
Choose the column phase that gives the best separation
but not at the cost of robustness or ruggedness.
Complete Resolution & Fast CLP Pesticide Analysis
Page 12
Agilent J&W DB-CLP1 and DB-CLP2
For 9 EPA Methods+ (More than any other CLP column pair!)
Page 13
Selectivity Differences
DB-624
DB-VRX
Page 14
Benzene and 1,2-Dichloroethane Separation
DB-Select 624UI<467>
30m x 0.53mm 30m x 0.32mm
DB-624
Co-elution
Page 15
Benzene and 1,2-Dichloroethane Separation
Baseline
Resolved
R= 1.82
Vendor R
G43
Vendor P
G43
R= 1.59 R= 1.38
DB-Select 624UI<467>
All 30m x 0.32mm
Resolution
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 17
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 18
Different Column I. D. Equal Phase Ratios
Time (min)
0 5 10 15 20
Carrier: Oven: 65° C Injection: Split Detector: FID
Column : DB-624 30 m, 0.32 mm, 1.8 m
Helium, 40 (cm/sec)
Column : DB-624 30 m, 0.53 mm, 3 m
Page 19
PHASE RATIO () Film Thickness
Column Dimensions Phase Ratio β
30 m x .53 mm x 3.0 m 44
30 m x .32 mm x 1.8 m 44
KC = k β
r
2df β =
Page 20
High Resolution Megabore Same Resolution - Faster Analysis!
“Increasing Sample Throughput
With High-Speed Megabore”
Application note 5988-5271EN
Page 21
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 22
Column Length and Efficiency (Theoretical Plates)
0.25 mm ID
n/m = 4630 (for k = 5)
Length (m) N
15 69,450
30 138,900
60 277,800
More Meters = More Plates = More Resolution
Page 23
Column Length and Resolution
Length X 4 = Resolution X 2
RaN aL
t a L
Upside = Cut a bunch off during routine inlet
maintenance and not lose a lot of Resolution
Page 24
Column Length VS Resolution and Retention:
Isothermal
Double the plates, double the time
but not double the the resolution
15 m 60 m 30 m
R=0.84
2.29 min
R=1.68
8.73 min
R=1.16
4.82 min
Page 25
Page 26
Column Length and Cost
15m 30m
60m
$ $ $ $ $ $ $
Resolution
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 27
Page 28
10 20 30 40 50 60
0.25
0.50
0.75
1.00
u (cm/sec)
h
He
H 2
Excessive Diffusion
Poor Mass Transfer
ū opt
Carrier Gas Maximum Resolution = Optimum Velocity = Slowest Velocity
Van Deemter Curves
N 2
Carrier Gas
Type Velocity Range (uopt – OPGV)
Nitrogen 10-17 cm/sec
Helium 22-40 cm/sec
Hydrogen 35-55 cm/sec
Page 29
Changes in Column Dimensions, Gas Type or
Velocity Require Changes in Temp Program Rates
Method Translation Software to the Rescue!
Page 30
Phenol’s – 30m x 0.25mm ID, 0.25μm, DB-5ms
Check Valleys
Page 31
Phenol’s – 20m x 0.18mm ID, 0.18μm, DB-5ms
0.54 mL/min, H2
(~47cm/sec)
Page 32
Slower than Best Efficiency? – must go faster!
(Sorry customer doesn’t want temperature program revealed)
Page 33
Phenol’s – 20m x 0.18mm ID, 0.18μm, DB-5ms
1 mL/min, (rounded up?)
higher than optimum,
BUT still better Resolution!
Page 34
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
Original Method
Page 35
Best Efficiency
New Velocity
(SLOWER)
New Temp.
Program
(SLOWER)
Page 36
Best Efficiency
23 minutes (Slower)
Better
Resolution
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
Original NEW
Resolution
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
Temperature, the TRUMP card
Page 38
Column Temperature Optimizing Temperature Programs
Most powerful variable
Changes Selectivity and Retention
Natural log (ln) relationship between retention and temperature
Most difficult to predict and develop
Often involves trial and error (Sorry)
Page 39
Capillary Flow Technology Capabilities
• Backflushing with Purged Devices
• 2D GC – Deans Switch / Heart Cutting
• Splitter to Multiple Detectors
• Multiple Columns/Multiple Detectors
Page 40
Purged Capillary Flow Devices
2-Way Splitter
with Makeup
3-Way Splitter
with Makeup Deans Switch
Page 41
Purged Union
(most recent)
9.78 psi 11.14 psi
FID A
S/S Inlet
FID B
PCM
Restrictor
6.54 mL/min
4.54 mL/min
<< 1mL/min
2mL/min
purge
restrictor
8.54 mL/min
Off
6.54 mL/min
Column 1
Column 2
Heart Cutting 2-D GC – How It Works
Valve off, no heart cutting– inject sample, initial separation on column 1
Page 42
FID A
S/S Inlet
FID B
PCM
On
6.54 mL/min
4.54 mL/min
6.54 mL/min
purge
restrictor
2mL/min 8.54 mL/min
<< 1mL/min
9.78 psi 11.14 psi
Restrictor
Column 1
Column 2
Heart Cutting 2-D GC – How It Works
Valve on – start heart cut from column 1 to column 2
Page 43
FID A
S/S Inlet
FID B
PCM
6.54 mL/min
4.54 mL/min
<< 1mL/min
9.78 psi 11.14 psi
2mL/min
purge
restrictor
8.54 mL/min
Off
6.54 mL/min
BP>Benzene
Restrictor
Column 1
Column 2
Heart Cutting 2-D GC – How It Works
Valve off – end heart cut, perform 2nd separation on column 2
Page 44
Calculator - Set Flows and Restrictor Size
Page 45
Page 46
4 5 6 7 8 9 10 11 12
2.09 mg/kg thiophene
benzene
Need to measure 0.02 to 2.00 mg/kg thiophene in pure benzene
HP-Innowax Column
60m x 0.53mm x 0.5um
Trace Thiophene in Benzene
Page 47
Analytical Precision
(15 runs over 5 days)
Avg Amt: 50 ppb
Std Dev: 0.95 ppb
RSD: 1.9%
Analysis of 20 ppb to 2 ppm using FID (2 uL splitless injection)
Trace Thiophene in Benzene
4 6 8 10 12 14 16 18 20
0.1
0.2
0.3
0.4
0.5
0.6
50 ppb thiophene
HP Plot Q
Column
4 6 8 10 12 14 16 18 20
0
100
200
300
400
500
Cut window
7.74 - 8.02 min
Innowax
Column
hydrocarbons
benzene
toluene
1,4-dioxane
Agilent’s Ultimate Pesticide Analysis System
• FPD
• µECD
• MS SIM
• MS Scan
1 gas chromatograph
1 injection
Page 48
Pesticides: Three Way Splitter with Makeup
1X method with 1:1:0.1 split FPD:MSD:ECD
3-Way
Splitter with
Makeup Auto-sampler
7890
GC
Column
Phosphorus FPD
30 m X 0.25 mm id X 0.25 um HP-5MS
5975C
MSD
uECD AUX EPC
3.8 psig
Page 49
3-Way Splitter System
Deactivated splitter operates to 350 C.
Using metal ferrules eliminates leaks and retightening
To µECD
Column in
Makeup gas from EPC
To MSD
To FPD
Page 50
Full scan TIC
SIM
µECD
5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00
FPD(P)
Milk Extract (1 injection)
Page 51
Front Inlet
Back Inlet
AUX 2 AUX 3AUX 1
MSD
Three Way
SplitterTwo Way
Splitter
FIDHP-5ms
Main Oven
DB-1ms
LTM
DB-17ms
LTM
R-1
R-2
R-3
R-4
HP-5ms 30m x 0.25 x 0.25 19091S-433 à Column 1
DB-1ms 15m x 0.25 x 0.25 122-0112 à Column 2
R1 = 0.30m x 0.1 restrictor à Column 4
R2 = 0.17m x 0.1 restrictor à Column 5
R3 = 0.50m x 0.25 restrictor à to FID
R4 = 1.00m x 0.18 restrictor à Column 3
HP-5ms 30m x 0.25 x 0.25 19091S-433 (Column 1)
DB-17ms LTM 15m x 0.25 x 0.25 122-4712LTM
DB-1ms LTM 15m x 0.25 x 0.25 122-0112LTM (Column 2)
Pre-Column = 1m x 0.25 uncoated FS
Pre
Column
Deans
Switch
LTM and Capillary Flow Technology, Possibilities! Metabolomics – Crops Research (Polar and Non-polar Analytes)
Page 52
Finally the Ultra Inert Story
•All that resolution is worth nothing if the peaks start
tailing and/or disappearing!
•Ultra Inert Columns and Liners provide the
maximum inertness available on the market.
•Activity only gets worse once you start injecting
samples. Start as inert as you can.
Page 53
Ultra Inert liners
• Touchless packaging
• Easy installation of new, clean liner
without risk of contamination from touching
• Includes non-stick plasma treated O-ring
Page 54
1. 1-Propionic acid
2. 1-Octene
3. n-Octane
4 4-Picoline
5. n-Nonane
6. Trimethyl phosphate
7. 1,2-Pentanediol
8. n-Propylbenzene
9. 1-Heptanol
10. 3-Octanone
11. n-Decane
Ultra Inert Test Mix - DB-5ms Ultra Inert vs. competitors
1
2 3
4 5
6 7
8
9 10 11
min 0 2 4 6 8 10
pA
10
12.5
15
17.5
20
22.5
25
27.5
Agilent J&W DB-
5ms Ultra Inert 30m x 0.25mm x
0.25um
(P/N 122-5532UI)
1
2 3 4
5
6 7
8
9 10 11
min 0 2 4 6 8 10
pA
6
8
10
12
14
16
18
20
1
2 3 4
5
6 7
8
9 10 11
min 0 2 4 6 8 10
pA
6
8
10
12
14
16
18
20
1
2 3
4
5
7
8
9 10
11
6 min 0 2 4 6 8 10
pA
8
10
12
14
16
18
Competitor
Column
Competitor
Column
Page 55
Semivolatiles Prone to Peak Tailing
(App. Note 5990-3416EN)
Page 56
Semivolatiles Prone to Peak Tailing
(App. Note 5990-3416EN)
Page 57
Resolution of benzo-b & k fluoranthene isomers
19.00 19.50
0
100000
500000
1000000
1500000
Time-->
Abundance
Benzo-b-fluoranthene
Benzo-k-fluoranthene
Resolution of 1.2
As good as it gets…it only gets worse!
Page 58
Conclusions for Better Resolution in GC
• Application Specific Stationary Phase - tuned for max R
• Smaller Diameter - loss in capacity, so small changes
• Longer, More Plates - big changes needed since it has a
small effect and it increases analysis times
• Optimum Carrier Gas Velocity - slowest carrier gas velocity
• 2D GC - more “chromatographic space” but adds complexity
• Multiple columns, inlets, detectors - single system with LTM
and Capillary Flow Technology
• Sharp Peaks - tailing, broadening, etc. loses resolution
Page 59
