the van deemter indoctrination
DESCRIPTION
Nitrogen cannot be used as carrier gas for GC. How sure are you about that? In this presentation we tackle what we call the “van Deemter indoctrination”. Take a look at our recent accomplishments and convince yourself to give it at try. Particularly now when more and more laboratories are suffering from inconsistent supplies of helium.TRANSCRIPT
THE VAN DEEMTER INDOCTRINATION
Nitrogen as Carrier Gas for GC?Are you kidding!
www.is-x.be
This is a funny story…
This is a funny story…about carrier gases in GC…
This is a funny story…about carrier gases in GC…and how we all got fooled.
Are you ready?
Keep Keep Keep Keep staringstaringstaringstaring in the centerin the centerin the centerin the center
Keep Keep Keep Keep staringstaringstaringstaring in the centerin the centerin the centerin the center
Keep Keep Keep Keep staringstaringstaringstaring in the centerin the centerin the centerin the center
YouYouYouYou are are are are sufferingsufferingsufferingsuffering fromfromfromfrominconsistent helium inconsistent helium inconsistent helium inconsistent helium supplysupplysupplysupply
YouYouYouYou have have have have problemsproblemsproblemsproblemsimplementingimplementingimplementingimplementing hydrogenhydrogenhydrogenhydrogen
ThereThereThereThere is is is is NO ALTERNATIVENO ALTERNATIVENO ALTERNATIVENO ALTERNATIVE
!!!!!!!!!!!!!!!!!!!!
We all know this story, don’t we?
However…
Have you ever considerednitrogen?
Probably not…
That’s because we all suffer fromthe “van Deemter indoctrination”
3Don’t worry, I’ve been a victim myself too…
Take a look at our experiencesand try to cure yourself too!
J. J. van Deemter was a briljant Dutch physicist. He worked for the Royal Dutch Shell laboratoryIn Amsterdam (The Netherlands) in the 1950s.
He was employed as chemical engineer and onlyhad little direct interest in chromatography.
In those days, the mathematical description ofthe chromatography process was rather complex.
In those days, the mathematical description ofthe chromatography process was rather complex.
This was mainly due to improper modelling.
van van van van DeemterDeemterDeemterDeemter J. J., J. J., J. J., J. J., ZuiderwegZuiderwegZuiderwegZuiderweg F. J. & F. J. & F. J. & F. J. & KlinkenbergKlinkenbergKlinkenbergKlinkenberg A. A. A. A. “Longitudinal diffusion and resistance to mass transfer as causes of nonideality in chromatography.”
Chem. Eng. Sci. 5:271-89, 1956.
However, after much experimentation and plotting, a very simple equation could be derived.
This equation, which is known as the van Deemterequation, was the first to describe the chromato-graphic process correctly.
H = A + B/u + CuH = height of one theoretical plate, cmu = average linear velocity, cm/s
In order to work under optimal conditions, plate height H has to be minimal.
H = A + B/u + Cu
THE A TERM = EDDY DIFFUSION
Peak broadening due to path lenghts differences in packedGC columns. A = 0 for capillary columns.
THE A TERM = EDDY DIFFUSION
Peak broadening due to path lenghts differences in packedGC columns. A = 0 for capillary columns.
THE A TERM = EDDY DIFFUSION
Peak broadening due to path lenghts differences in packedGC columns. A = 0 for capillary columns.
THE A TERM = EDDY DIFFUSION
Peak broadening due to path lenghts differences in packedGC columns. A = 0 for capillary columns.
THE A TERM = EDDY DIFFUSION
Peak broadening due to path lenghts differences in packedGC columns. A = 0 for capillary columns.
THE B TERM = LONGITUDINAL DIFFUSION
Peak broadening due to multidirectional diffusion. Indirectly proportional to flowrate.
THE B TERM = LONGITUDINAL DIFFUSION
Peak broadening due to multidirectional diffusion. Indirectly proportional to flowrate.
THE B TERM = LONGITUDINAL DIFFUSION
Peak broadening due to multidirectional diffusion. Indirectly proportional to flowrate.
THE B TERM = LONGITUDINAL DIFFUSION
Peak broadening due to multidirectional diffusion. Indirectly proportional to flowrate.
THE C TERM = RESISTANCE TO MASS TRANSFER
Peak broadening due to equilibrium kinetics in mobile andstationary phase. DirectlyDirectlyDirectlyDirectly proportionalproportionalproportionalproportional totototo flowrateflowrateflowrateflowrate!!!!
Stationary phase
THE C TERM = RESISTANCE TO MASS TRANSFER
Peak broadening due to equilibrium kinetics in mobile andstationary phase. DirectlyDirectlyDirectlyDirectly proportionalproportionalproportionalproportional totototo flowrateflowrateflowrateflowrate!!!!
Stationary phase
THE C TERM = RESISTANCE TO MASS TRANSFER
Peak broadening due to equilibrium kinetics in mobile andstationary phase. DirectlyDirectlyDirectlyDirectly proportionalproportionalproportionalproportional totototo flowrateflowrateflowrateflowrate!!!!
Stationary phase
THE C TERM = RESISTANCE TO MASS TRANSFER
Peak broadening due to equilibrium kinetics in mobile andstationary phase. DirectlyDirectlyDirectlyDirectly proportionalproportionalproportionalproportional totototo flowrateflowrateflowrateflowrate!!!!
Stationary phase
Both B and C terms react opposite to flowratechanges.
Both B and C terms react opposite to flowratechanges.
There is an optimal flow!
This is how a typical van Deemter curve looks like.
0
0,5
1
1,5
2
2,5
3
3,5
0 0,5 1 1,5 2 2,5
H, cm
Flow rate, mL/min
And this is the optimal flow region.
0
0,5
1
1,5
2
2,5
3
3,5
0 0,5 1 1,5 2 2,5
H, cm
Flow rate, mL/min
Optimal flow region
Key variables that determine curve shape and optimalflow region are column ID and carrier gas type.
Key variables that determine curve shape and optimalflow region are column ID and carrier gas type.
Key variables that determine curve shape and optimalflow region are column ID and carrier gas type.
0,0
0,5
1,0
1,5
2,0
2,5
3,0
0 0,5 1 1,5 2 2,5
H, cm
Flow rate, mL/min
Nitrogen
Helium
Hydrogen
Influence of carrier gas type.
0,0
0,5
1,0
1,5
2,0
2,5
3,0
0 0,5 1 1,5 2 2,5
H, cm
Flow rate, mL/min
Test compound: 2-ethyl hexanoic acid
Column: 20 m x 0.18 mm I.D. x 0.18 µm df
Phase: Rxi-5 Sil MS
Manufacturer: Restek (# 43602)
Nitrogen
Helium
Hydrogen
Experimental details.
Van Deemter tells us: “helium is acceptable”.
Van Deemter tells us: “helium is acceptable”.
We advise to use helium for all MS applications,but do we really need it for GC/FID work ?
Van Deemter tells us: “hydrogen is best”.
Van Deemter tells us: “hydrogen is best”.
We advise to use hydrogen for fast(er) GC applications. In combination with MS you have tocope with a loss in sensitivity and a risk of activity.
Approach when keeping the same column:
Approach when keeping the same column:
Divide the isothermal stages of your oven program by two and double all the programming rates (headpressure stays the same).
Approach when keeping the same column:
Divide the isothermal stages of your oven program by two and double all the programming rates (headpressure stays the same).
Thus:
30C (2 min) to 250C at 10C/min (Helium)=
30C (1 min) to 250C at 20C/min (Hydrogen)
Example 1: Solvent impurity analysis.
Example 1: Solvent impurity analysis.
Minutes
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34
pA
-10000
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
100000
110000
120000
pA
-10000
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
100000
110000
120000
TRACE GC-FID A
Unknown
Helium: 30 minutesColumn: 20 m x 0.18 mm I.D.
Example 1: Solvent impurity analysis.
Minutes
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34
pA
-10000
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
100000
110000
120000
pA
-10000
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
100000
110000
120000
TRACE GC-FID A
Unknown
Minutes
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
pA
-10000
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
100000
110000
120000
130000
140000
150000
160000
pA
-10000
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
100000
110000
120000
130000
140000
150000
160000TRACE GC-FID A
Unknown
Helium: 30 minutesColumn: 20 m x 0.18 mm I.D.
Hydrogen: 15 minutesColumn: 20 m x 0.18 mm I.D.
A little bit more in detail.
A little bit more in detail.
Minutes
12 14 16
Helium
A little bit more in detail.
Minutes
12 14 16 6 7 8
Helium Hydrogen
Example 2: Process analysis.
Example 2: Process analysis.
min0 2 4 6 8 10 12
pA
3.5
4
4.5
5
5.5
6
6.5
7
FID1 A, (1603JV04.D)
0.898
FID2 B, (1603JV04.D)
Example 2: Process analysis.
min0 2 4 6 8 10 12
pA
3.5
4
4.5
5
5.5
6
6.5
7
FID1 A, (1603JV04.D)
0.898
FID2 B, (1603JV04.D)
Helium: 44 minutesHydrogen: 14 minutes!MXT column: 10 m x 0.53 mm I.D.
Example 3: Environmental analysis
Example 3: Environmental analysis
Minutes
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
pA
7.5
10.0
12.5
15.0
17.5
20.0
22.5
25.0
27.5
30.0
32.5
35.0
37.5
40.0
42.5
pA
7.5
10.0
12.5
15.0
17.5
20.0
22.5
25.0
27.5
30.0
32.5
35.0
37.5
40.0
42.5
TRACE GC-FID-ar
SV MegaMix
Example 3: Environmental analysis
Minutes
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0
pA
7.5
10.0
12.5
15.0
17.5
20.0
22.5
25.0
27.5
30.0
32.5
35.0
37.5
40.0
42.5
pA
7.5
10.0
12.5
15.0
17.5
20.0
22.5
25.0
27.5
30.0
32.5
35.0
37.5
40.0
42.5
TRACE GC-FID-ar
SV MegaMix
Helium: 25 minutesColumn: 20 m x 0.18 mm I.D.
Hydrogen: 6 minutes!Column: 10 m x 0.10 mm I.D.
But beware,
But beware,
It’s a struggle to convice company safety officers.
But beware,
It’s a struggle to convice company safety officers.You need to invest in sensors.
But beware,
It’s a struggle to convice company safety officers.You need to invest in sensors.You need to invest in generators.
But beware,
It’s a struggle to convice company safety officers.You need to invest in sensors.You need to invest in generators.
And sometimes it simply does not work!
Example 1: Loss in capacity.
Minutes
3,2 3,3 3,4 3,5 3,6 3,7 3,8 3,9 4,0 4,1 4,2
pA
4
6
8
10
12
14
16
18
20
22
24
26
28
pA
4
6
8
10
12
14
16
18
20
22
24
26
28
3,380
3,443
3,588
3,682
3,797
4,000
TRACE GC-FID-AR
cumeen
5-10-2009 13-35-40 CP5CB H2 cumeen.dat
Retention Time
Name
TRACE GC-FID-AR
cumeen
24-09-2009 10-11-54 CC656 H2 cumeen.dat
TRACE GC-FID-AR
cumeen
29-09-2009 12-36-21 CC657 H2 cumeen.dat
Reference:0.32 mm ID, 1.2 µm df (H2)
0.15 mm ID, 0.6 µm df (H2)
0.15 mm ID,1.2 µm df (H2)
Example 2: Impurities in styrene.
Styrene Ethylbenzene
Example 2: Impurities in styrene.
Styrene Ethylbenzene
Results overview.
0
100
200
300
400
500
600
700
800
900
1000
150170190210230250
Conc, ppm
Injection temp, C
Ethylbenzene (He) Ethylbenzene (H2) Indane (He) Indane (H2)
Results overview.
0
100
200
300
400
500
600
700
800
900
1000
150170190210230250
Conc, ppm
Injection temp, C
Ethylbenzene (He) Ethylbenzene (H2) Indane (He) Indane (H2)
Internal standard
Results overview.
0
100
200
300
400
500
600
700
800
900
1000
150170190210230250
Conc, ppm
Injection temp, C
Ethylbenzene (He) Ethylbenzene (H2) Indane (He) Indane (H2)
Ethylbenzene
And finally…
Last but not least…
Nitrogen…
Van Deemter tells us: “nitrogen cannot be used”.
Is this where it ends?
Van Deemter tells us: “nitrogen cannot be used”.
Is this where it ends?
Van Deemter tells us: “nitrogen cannot be used”.
We have implemented several nitrogen methodssuccessfully the last year.
We have implemented several nitrogen methodssuccessfully the last year.
We primarely aim at GC/FID methods.
We have implemented several nitrogen methodssuccessfully the last year.
We primarely aim at GC/FID methods.
We have implemented several nitrogen methodssuccessfully the last year.
We primarely aim at GC/FID methods.
7/10 instruments!
Approach when keeping the same column:
Approach when keeping the same column:
Just leave everything as it is (including head pressure)!
Approach when keeping the same column:
Just leave everything as it is (including head pressure)!
Thus:
30C (2 min) to 250C at 10C/min (Helium)=
30C (2 min) to 250C at 10C/min (Nitrogen)
Example 1: Test mix.
Example 1: Test mix.
2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 4.60 4.80 5.00
9.00
10.00
11.00
12.00
13.00
14.00
15.00
8 - 2.8159 - 2.867
10 - 3.263
11 - 4.06312 - 4.147
13 - 4.505
14 - 4.785
15 - 4.827
16 - 4.873
min
pA
Carrier N2 1.5 mL #3 XIL-350_Mix He Front_FID2
HeliumColumn: 20 m x 0.18 mm I.D.
Example 1: Test mix.
2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 4.60 4.80 5.00
9.00
10.00
11.00
12.00
13.00
14.00
15.00
8 - 2.8159 - 2.867
10 - 3.263
11 - 4.06312 - 4.147
13 - 4.505
14 - 4.785
15 - 4.827
16 - 4.873
min
pA
Carrier N2 1.5 mL #3 XIL-350_Mix He Front_FID2
2.00 2.20 2.40 2.60 2.80 3.00 3.20 3.40 3.60 3.80 4.00 4.20 4.40 4.60 4.80 5.00
9.00
10.00
11.00
12.00
13.00
14.00
15.00
8 - 2.8159 - 2.867
10 - 3.263
11 - 4.06312 - 4.147
13 - 4.505
14 - 4.785
15 - 4.827
16 - 4.873
min
pA
Carrier N2 1.5 mL #3 XIL-350_Mix He Front_FID2
HeliumColumn: 20 m x 0.18 mm I.D.
NitrogenColumn: 20 m x 0.18 mm I.D.
Example 2: Butyl acrylate.
Example 2: Butyl acrylate.
HeliumColumn: 60 m x 0.32 mm I.D.
Example 2: Butyl acrylate.
HeliumColumn: 60 m x 0.32 mm I.D.
NitrogenColumn: 60 m x 0.32 mm I.D.
A little bit more in detail.
A little bit more in detail.
Helium
A little bit more in detail.
Helium Nitrogen
A little bit more in detail.
Helium Nitrogen
Example 3: Narrow bore column
Example 3: Narrow bore column
2.00 min2.00 min2.00 min2.00 min
NitrogenColumn: 10 m x 0.1 mm I.D.
Why does it work?
Why does it work?
Van Deemter is measured under isothermal conditions
Why does it work?
Van Deemter is measured under isothermal conditionsVan Deemter is valid for optimal conditions
Why does it work?
Van Deemter is measured under isothermal conditionsVan Deemter is valid for optimal conditions
Why does it work?
Van Deemter is measured under isothermal conditionsVan Deemter is valid for optimal conditions
InjectionSeptum
LinerColumn
Why does it work?
Van Deemter is measured under isothermal conditionsVan Deemter is valid for optimal conditions
InjectionSeptum
LinerColumn
Other methods:
AcrylatesDi- and triaminesBTEXNon-aromaticsPrimary aryl alcoholsEthylacetateEthanolaminesAlcoholsAcetic acidLight hydrocarbons
Don’t be afraid to challengevan Deemter!
More information?
Dr. Joeri VercammenDr. Joeri VercammenDr. Joeri VercammenDr. Joeri VercammenManaging Expert ISManaging Expert ISManaging Expert ISManaging Expert IS----XXXX
[email protected]://www.linkedin.com/in/joerivercammen
Also check out our other presentations!
Acknowledgements:
C. De WeerdtE. Van BrusselA. De CaluwéR. HeusP. RyckaertM. Van Lancker