Advances in Capillary Columns For Gas Chromatographic

Applications

Shawn Reese, Roy Lautamo, Chris Cox

Gianna Barlupi, Rick Morehead, Jason Thomas, Gary Stidsen, and Frank Dorman

Old Technology?

• Gas Chromatography is 50 years old! Like wine and cheese it seems to keep getting better!!

• Packed columns (over 100 different phases)• Capillary debut commercially in 1970’s • Phase development parallels some packed column

phases

Phase Development – Early Phases

Si O Si O Si O Si

5 95Rtx -5

Si O Si O Si

nRtx-1

O nRtx-Wax

Si O Si O Si O Si

14 86Rtx -1701

CN

Capillary Phase Technology

• Pendant siloxanes do not show large viscosity changes with temperature (from -40 to 400oC)

• High polarity applications require a wax phase which has a high temperature limit of 260

• Deactivation technology varies from manufacturer and can be a limiting factor on what is possible

• Pendant phases are fairly similar from manufacturer to manufacturer

What Does the Industry Need?

• Low Bleed?– What is bleed? Can it be stopped?

• “MS” Phases?– Application of low-bleed technology?

• Reproducible columns?– Why do our manufacturing profiles matter to you?

• Inertness– Professor Walt Jennings, Riva 2004

• Selectivity-specific applications– PCB’s, Dioxins, PBDPE’s, pesticides

What is Bleed?• Common bleed ions associated with phases that contain

PDMS

• LaChatlier’s principle works against us due to the volatility of the products.

O

Si

O

Si

O

Si

MW = 222 - 15 = 207 M+

O

Si

O Si

O

Si

OSi

MW = 222 - 15 = 281 M+

Slowing Down Decomposition• “G” groups spreads Si-O groups out so that they cannot

“back-bite” each other and form small cyclic rings.

Bleed Mass Spectrum

50 100 150 200 250 300 350 400 4500

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

m/z-->

Abundance Scan 3634 (24.939 min): C0830013.D207

73 281

4496 133

177 253156 327 355 475384 455430407230

Trimethylsilyl+

Pentamethylcyclotrisiloxane+

Heptamethylcyclotetrasiloxane+

Backbone modified phases slow down the back-biting mechanism

Si O Si O Si

R

R

O SiG Si

x y

O Si

z

Rtx-440, Rtx-PCB, Rtx-XLB, Rtx-dioxin2

Low-Bleed – 1st Generation (90’s)• What drives innovation? Introduction of “ms” phases!

• As GC manufacturers make more sensitive detectors demands from the phases increase.

• 1st generation was a “5” in the backbone, first produced by Sveda (1951!)…did not appear in GC phases until early 1990’s.

• Thermal decomposition decreased due to “stiffining” of the backbone chain.

Si O Si O Si O Si

Rtx-5Silms

Si

x y

Low Bleed Next Generation21st Century

• “Next” Generation was application of “other” backbone modified groups, and “new” pendant groups

• Selectivity can vary dramatically if the pendant groups are very different from one another, and the backbone Group “G” is significantly different than “phenyl”.

Si O Si O Si

R

R

O SiG Si

x y

O Si

z

Rtx-440, Rtx-PCB, Rtx-XLB, Rtx-dioxin2

What “G” groups have been used?• Literature reports the following groups:

O

CH3H3C

H3C CH3

Si

CC each intersection represents aboron atom and each carbonand boron atom has a hydrogenbonded to it which has beenomitted f or clarity.

Deactivations – A new problem?

• Bench-top mass spectrometers in the early 90’s had sensitivity similar to the standard FID

• Today, sensitivity of bench-top mass spectrometers are better than the standard FID, and the column can interfere with detection .

• Inertness is a more serious issue now with detection below nanogram levels on MS.

What else can we do?

• As the mechanism on the previous slide implies, chemically inert polymers demand the most stringent synthetic conditions

• We have devised “systems” that limit the polymers ability to “find” proton sources during phase procurement through deactivation techniques and through new, proprietary syntheses.

Restek’s Exceptionally InertGC Columns (Rxi)

• New column technology developed by Chemists at Restek and new research lab, Restek West

• Rxi-1ms, Rxi-5ms• New deactivation chemistry, new polymer chemistry,

new manufacturing process• Results in columns that are:

– Highly Inert– Reproducible– Low bleed

Reproducibility = Reliablity for the user!

• In-house QC results• Comparison between manufacturers• What do you need?

Bleed of Manufactured Columns

Column Bleed DistributionRxi-5ms (30m x 0.25mm, 0.25um)

0

20

40

60

80

100

1.0 2.0 3.0 4.0

Bleed (pA)

Fre

qu

en

cy

Mean = 1.9pASD = 0.65

Rxi-5ms Bleed Study (30m x 0.25mm, 0.25um film)

Minutes

0 2 4 6 8 10 12 14 16 18 20

pA

0

2

4

6

8

10

12

14

16

18

pA

0

2

4

6

8

10

12

14

16

18927-A

Name927-A 927-A 927-A 927-A 927-A

Reference Peak

1ng tridecane

330330ooCC

350350ooCC

Rxi-5msRxi-5ms

Columns include:

5% diphenyl 95% dimethyl &

Silarylene based phases

(30m x 0.25mm, 0.25um)

Detector: FID

2

4

6

Retention Time “Windows” Ultimate Reproducibility

Column-to-Column

• Exact Length– Is this important?

• Isothermal testing– Comparison of batch to batch reproducibility

• In-house QC results– Film thickness

– Coating efficiency

– Selectivity

Rxi-5ms Column Reproducibility

Film Thickness

Capacity Factor (k) DistributionRxi-5ms (30m x 0.25mm, 0.25um film)

0

50

100

150

6.2 6.4 6.6 6.8 7.0Capacity Factor (k)

Fre

qu

en

cy

Coating Efficiency

Plate/Meter Distribution Rxi-5ms (30m x 0.25mm, 0.25um)

0

10

20

30

40

50

60

3900 4000 4100 4200 4300 4400 4500 4600Plate/Meter

Fre

qu

en

cy

Selectivity

RI of UndecanolRxi-5ms (30m x 0.25mm, 0.25um)

0

50

100

150

1372.2 1372.5 1372.8 1373.1 1373.4

Retention Indice (RI)

Fre

qu

ency

Selectivity

RI of AcenaphtheneRxi-5ms (30m x 0.25mm, 0.25um)

0

20

40

60

80

1461.3 1461.6 1461.9 1462.2 1462.5 1462.8 1463.1 1463.4

Retention Indice (RI)

Fre

qu

ency

Inertness• 0.5ng on-column concentration

– Basic compound

– Acidic compound

• 2ng on-column comparison between manufacturers – Chromatographic peaks of pyridine

– Response factor

• This is the area that is a “WIP”….we have come a long way…..can it get better? We’ll show Rxi as an example of what all columns should be like!

Rxi-5ms Column Inertness(30m x 0.25mm, 0.25um)

Basic CompoundsBasic Compounds

Acidic CompoundsAcidic Compounds

2.25 2.30 2.35 2.40 2.45 2.50 2.55 2.60

0

5000

10000

15000

20000

25000

30000

Time-->

Abundance

2.25 2.30 2.35 2.40 2.45 2.50 2.55 2.60

0

5000

10000

15000

20000

25000

30000

Time-->

Abundance 0.5 ng on-column

PyridinePyridineNN--nitrosonitroso dimethylaminedimethylamine

7.10 7.15 7.20 7.25 7.30 7.350

500

1000

1500

2000

2500

3000

3500

4000

Time-->

Abundance

7.10 7.15 7.20 7.25 7.30 7.350

500

1000

1500

2000

2500

3000

3500

4000

Time-->

Abundance 0.5 ng on-column

2,42,4--dinitrophenoldinitrophenol

RF = 0.14RF = 0.14

m/z 184

m/z 79m/z 74

2ng PyridineRxi-5ms (30m x 0.25mm, 0.25um)

Rxi-5ms Column Inertness(30m x 0.25mm, 0.25um)

Mean RF for 2ng on-column of pyridine

0.807 0.8060.649 0.651 0.624 0.639 0.675

0.000

0.200

0.400

0.600

0.800

1.000

Rxi-5m

s

man

ufactu

rer A

man

ufactu

rer B

man

ufactu

rer C

man

ufactu

rer D

man

ufactu

rer E

man

ufactu

rer F

Res

po

nse

Fac

tor

(RF

)

Rxi-5ms Column Inertness(30m x 0.25mm, 0.25um)

Mean RF of 2ng on-column 2,4-Dinitrophenol

0.249

0.181

0.236

0.168

0.2350.191 0.202

0.000

0.050

0.100

0.150

0.200

0.250

0.300

Rxi-5m

s

man

ufac

ture

r A

man

ufac

ture

r B

man

ufac

ture

r C

man

ufac

ture

r D

man

ufac

ture

r E

man

ufac

ture

r F

Re

sp

on

se

fa

cto

r

Inertness Probes1,6-Hexanediol

Response Factor

-0.30

0.20

0.70

1.20

0 20 40 60 80 100 120 140 160

Column

RF

(vs

C13

)

4-Chlorophenol Response Factor

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 20 40 60 80 100 120 140 160

Column

RF

(vs

C13

)

1-Undecanol Response Factor

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 20 40 60 80 100 120 140 160

Column

RF

(vs

C13

)

1-Decylamine Response Factor

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 20 40 60 80 100 120 140 160

Column

RF

(vs

C13

)

Applications• Environmental

– Semivolatile analysis

• Clinical– Acidic and basic drugs

Rxi-5msSemivolatiles (5ng on-column)

Rxi-5msSemivolatiles (5ng on-column)

Rxi-5msAnalysis of Drug Compounds

Rxi-5msAnalysis of Drug Compounds

Summary of Rxi Columns

• Unsurpassed inertness for active compounds• Low bleed• Excellent column to column manufacturing

• Excellent overall performance due to combination of inertness, low bleed, and reproducible manufacturing process

Special Selectivity?

• Application specific – not everyone is doing congener specific PCB analysis

• Utilizes low-bleed technology, and incorporates many manufacturing techniques as our Rxi process

• These polymers are Restek specific; cannot be found from other manufacturers

Rtx-Dioxin2

• New phase that is specially “tuned” for dioxin analysis

Rtx-Dioxin 2

Rtx-PCBCongener Specific Analysis

• Resolves most PCB’s into absolute separation or “MS-resolvable” separations (differing Cl numbers).

• A low bleed phase – will allow for high temperature applications for “dirty” samples.

Rtx-PCB place picture here

Rtx-5SilMs – Shape selectivity

Rtx-17 Fused Silica Column

• Rtx-50 vs Rtx-17– Both 50% phenyl / 50% methyl

• Selectivity between Rtx-50 and Rtx-17 is different

• GCxGC separations coupled to a 5 or 1• Equivalent selectivity to DB-17

Rtx-50 Rtx-17

Acknowledgements

• Chris English and innovations group for applications

• Roy Lautamo for suggestions on how to proceed• Shimadzu for kind invitation and providing

support for this trip!!