Optimizing Column Selection for
Gas Chromatography Applications and
Speed of Analysis
Lee Marotta, Sr. Field Application Scientist
P ki El
PerkinElmer
1
© 2011
2009 PerkinElmer
Ask Several Questions before Selecting a Column
What is the component composition
 Homologous series of non-polar or slightly polar or polar analytes
 Mixture of polar and non
non-polar
polar analytes
 Volatile components (volatility less than naphthalene)
 Semi-volatile components (volatility greater than naphthalene)
 A composite of both volatile and semi volatile components
What is the analyte concentration
Is sample throughput a concern
Is resolution a concern
Are there many compounds to separate
Is your sample “clean” or “dirty”
How is your Gas Chromatograph configured
 Capillary, packed or PTV injector
 Detector
 Backflushing capability
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Chromatographic Process
Compounds volatilized by sample introductory system are introduced into
column and focus at the head of the analytical column
Mobile
M
bil Ph
Phase
(carrier gas)
Separation
 Stationary (liquid) Phase
 Compound Boiling Point (oven temperature program)
 Carrier Flow Rate
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Stationary
Phase
Chromatographic Process - Separation
Analytes more soluble in the
stationary (liquid) phase will be
retained longer
As column temperature increases,
less volatile compounds which
remained focused will become
volatile again and travel down
column interacting with stationary
phase
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Analogy - Vinegar and water or
Vinegar and oil
Optimizing for Productivity
Using Efficient Columns
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© 2011
2009 PerkinElmer
Theoretical Plates: N = 5.545 (tr/Wh)2
Benefits of efficiency
 Enhanced resolution
 Improved detection limits
 Faster analysis
Column divided into
theoretical plates
The column of choice
 Narrow bore (id) column
 Thinner film
HETP (mm)
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Variables affecting Resolution: Rs = 2(tr2 – tr1) / W1 + w2)
R=
1
L
k
α-1
4
H
k+1
α
Film Thickness df
Liquid Phase
I.D
Length
g
7
Resolution: Narrower is Better than Longer
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10 minutes
30 minutes
20m column x 0.32mm id
60m column x 0.32mm id
10 minutes
10 minutes
20m column x 0.32mm id
20m column x 0.25mm id
R ~ L1/2
R ~ 1/I.D.
14 minutes versus 45 minutes – Fragrance
Faster
Improved Resolution
Elite 1 – 10m x 0.18mm x 0.4um
fr_gold_0808_04
Scan EI+
TIC
1.58e9
100
%
1
Time
1.00
2.00
3.00
4.00
5.00
6.00
7.00
8.00
9.00
10.00
11.00
12.00
13.00
Eli 1 – 60m
Elite
60 x 0.25mm
02
x 0.5um
0
fr_gold_0808_08
Scan EI+
TIC
1.13e10
100
%
3
Time
0.61
9
5.61
10.61
15.61
20.61
25.61
30.61
35.61
40.61
EPA Method TO-17: Volatile Organic Compounds in Air
PE Elite 5 – 60m x 0.25mm x 1.0um
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Focusing of volatile components
PE Elite 1 – 30m x 0.25mm x 0.5um
Thin film
Not optimum stationary phase
PE Elite 5 – 60m x 0.25mm x 1.0um
Thicker film
Improved stationary phase (additional selectivity)
Slower flow rate
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Shorter, more efficient column with optimum stationary phase
Elite 624 – 20m x 0.18mm x 1.0um
 Able to focus very volatile gases
 Reduced analysis time from 30min
to 14min
 Didn’t need to use thicker film –
reduces MS maintenance
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Optimizing for Productivity
Using Mass Spectrometry
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© 2011
2009 PerkinElmer
Why GC/MS?
Both a Universal and Selective Detector
Enables aggressive detection limits
Positive Identification with standard or user library spectrum
Interference Free Quantification – chromatographic separation may
not be necessary
Combines separation and identification techniques
 3 dimensional data – Intensity,
Intensity Time
Time, Identity
Provides both quantitative and qualitative information about your
sample
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Universal and Specific typically Interference Free Integration
good_sample_2 1646 (24.450) Cm (1646-1673x2.0
9.10e4
43
100
good_sample_2 1656 (24.582) Cm (1656-1688:16
1.19e5
43
100
55
41
good_sample_2 1666 (24.716) Cm (1666-1689x2.0
1.45e4
55
100
43
41
55
%
%
29 39
30
57
67 70 85
88 95
0
30
108
58
78
98
53
68 85
124
m/z
38
67
57
45
118
91 95
98
124
56
m/z
58
78
91
97
111
0
38
111
%
39
98
118
71
m/z
38
58
78
98
good_sample_2 Sm (Mn, 1x3)
118
Scan EI+
85
1.95e4
24.50
100
112 126
0
%
24.74
4
good_sample_2 Sm (Mn, 1x3)
25.21
Scan EI+
111
2.72e4
24.62
100
25.33
%
24.13
1
good_sample_2 Sm (Mn, 1x3)
Scan EI+
TIC
1.55e6
24.53
100
%
24
23 74
23.74
15
23 94
23.94
24 14
24.14
25.26
24.97
24.14
24 34
24.34
24 54
24.54
24 74
24.74
24 94
24.94
25 14
25.14
Time
25.34
25
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Optimizing for Productivity
Using Backfush and Dean Switch
Techniques in Conjunction with
Column Technology
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© 2011
2009 PerkinElmer
Benefits:
•Extends column life
•Increases interval before required
maintenance
•Faster analysis
•More samples analyzed in a day
Methanol in Crude Oil
(ASTM D-7059)
Benzene and
B
dT
Toluene
l
iin
Gasoline
(ASTM D-3606)
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© 2009 PerkinElmer
Methanol in Crude Oil Analytical Configuration-Automated
Temperature Programmable (PSS) Injector
•Select a starting inlet temp which will retain most of the high boiling point
crude components in inlet while volatilizing the required lower boiling point
targets of interest
•Prevents most of the crude from entering the pre-column
S f TM (micro
Swafer
( i
channel
h
l flow
fl switcher)
it h )
• Provides ability to pressure tune
• Enables backflushing during chromatography
• Prevents unwanted analytes to enter analytical column
• Easy to use – Pressure and time
PSS @ 125°C
S-Swafer
6cm x 0.100mm restrictor
30m x 0.530mm x 5.0µm
µ Elite-1
Non-polar column to retain nonpolar crude components
24 psig
nitrogen
20 psig
nitrogen
FID @ 300°C
25cm x 0.150mm restrictor
GC oven = 125(1)-25-300(0)
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Polar Column to separate MeOH from non-polar
components that eluted onto analytical column
Conditions to Backflush
Increase split Flow
PSS @ 450°C
S-Swafer
6cm x 0.100mm restrictor
30m x 0.530mm x 5.0µm
µ Elite-1
10psig
nitrogen
20psig
nitrogen
FID @ 300°C
Reduce inlet pressure
25cm x 0.150mm restrictor
GC oven = 125(1)-25-300(0)
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Polar Column
Robustness
Methanol
M
Group of very volatile
hydrocarbons from crude
that eluted onto polar
column
IS
Injection # 20
Injection # 157
20 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0 5.2 5.4 5.6 5.8
ASTM D-3606: Benzene and Toluene in Gasoline
Split Injector
S-Swafer
FID 2
F d Silica
Fused
Sili Restrictor
R ti t
30m x 0.250mm x 0.25µm Elite-1
P1
P2
FID 1
50m x 0.250mm x 0.4µm TCEP
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Isothermal GC oven
Toluene
Iso-octane
Chromatography is investigated
from restrictor in fid 2 makingg it
simple to attain what is eluting
from pre-culumn …a fast, easy
way of determining backflush time
Benzene
Ethanol
Determining Backflush Time
Backflush
Point
0 00
0.00
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0 10
0.10
0 20
0.20
0 30
0.30
0 40
0.40
0 50
0.50
0 60
0.60
0 70
0.70
0 80
0.80
0 90
0.90
1 00
1.00
1 10
1.10
1 20
1.20
1 30
1.30
1 40
1.40
1 50
1.50
1 60
1.60
1 70
1.70
1 80
1.80
1 90
1.90
Toluene
Ben
nzene
Ethanol
Gasoline Sample
2.80 2.85 2.90 2.95 3.00 3.05 3.10 3.15 3.20 3.25 3.30 3.35 3.40 3.45 3.50 3.55 3.60 3.65 3.70 3.75 3.80 3.85 3.90 3.95
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… Results in Under Four Minutes!
Conclusion
A brief general statement
 For semi-volatiles (environmental), PE Elite 5 – 20m x 0.18mm x 0.4um
 For high molecular weight non-polar compounds, PE Elite 1 – 10m x 0.25mm x
0 1 iis great!t!
0.1um
 For focusing volatiles on a non-polar column, a thicker film is preferred. If semivolatiles are not present, using a volatile stationary phase like an Elite 624, 1301,
volatiles, etc. will allow a thinner film
 Polar compounds may not chromatograph properly on a non-polar stationary
phase. Concern … polar stationary phases like a Wax is not as robust as nonpolar columns and have strict temperature limits ie 240 degrees.
 Most columns have temperature
p
limits. This mayy dictate yyour column selection
 There are specialty columns for active compounds like Amines, Carboxylic Acids,
sulfur components, etc. that may require consideration
Disadvantages to narrow id columns


Stationary phase capacity (increase split or dilute sample)
Linearity
All products discussed in this presentation are available on www.perkinelmer.com
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we appreciate your time
Questions?
lee marotta@perkinelmer com
[email protected]
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