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

www.is-x.bej.vercammen@is-x.behttp://www.linkedin.com/in/joerivercammen

Also check out our other presentations!

Acknowledgements:

C. De WeerdtE. Van BrusselA. De CaluwéR. HeusP. RyckaertM. Van Lancker