Restek Corporation Restek Corporation www.restekcorp.com www.restekcorp.com The Design of High Temperature Capillary Gas Chromatography Columns Based on Polydimethylsiloxane Jarl Snider, D. J. Hotnisky, Kristi Sellers, Jarl Snider, D. J. Hotnisky, Kristi Sellers, Dinesh V. Patwardhan Dinesh V. Patwardhan Ph. D. Ph. D.
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Polydimethylsiloxane Gas Chromatography Columns Based on ... · The Design of High Temperature Capillary Gas Chromatography Columns Based on Polydimethylsiloxane ... PDMS D 3 /D 4
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The Design of High Temperature CapillaryGas Chromatography Columns Based on
Polydimethylsiloxane
Jarl Snider, D. J. Hotnisky, Kristi Sellers,Jarl Snider, D. J. Hotnisky, Kristi Sellers,Dinesh V. PatwardhanDinesh V. Patwardhan Ph. D.Ph. D.
Outline
BackgroundBackground
Definition of TerminologyDefinition of Terminology
Unique Attributes of High Temperature ColumnUnique Attributes of High Temperature Column
ApplicationsApplications
ConclusionsConclusions
Polydimethylsiloxane
Si O
CH3
CH3
nHHO
Sin
CH3
CH3
OSi
CH3
CH3
CH3CH3
H3C
CH3
Si O
Thermal Stability of PDMS
Adapted from Siloxane Polymers, ed. Clarson & Semlyen, 1993.
Beginning ofdecomposition
Bleed
•• Chromatography of “loose” silicones from theChromatography of “loose” silicones from thecolumncolumn
temperature
pA
Bleed
Typical Chemical Structure of Bleed
S i
O O
S i S i
O
M e
M e
M e
M e
M e
M e
D 3
Me Me
Me
Me
Me Me
Me
Me
OSiO
O
Si
SiO
Si
D4
Challenge
•• Since the decomposition temperature for PDMS isSince the decomposition temperature for PDMS is343°C, it is a challenge to make a column that is343°C, it is a challenge to make a column that isstable and has low bleed at 380°C.stable and has low bleed at 380°C.
Origin of Bleed
•• Polymer SynthesisPolymer Synthesis
•• Oligomers that are “created” in a column’s lifetimeOligomers that are “created” in a column’s lifetime
Origin of Bleed...
•• Polymer SynthesisPolymer Synthesis
Adapted from Inorganic Polymers, Mark, Allcock, & West 1992.
Polymer Synthesis
•• Silicone Polymers can be synthesized using wellSilicone Polymers can be synthesized using wellknown catalysts (KOH, HCl) under equilibrationknown catalysts (KOH, HCl) under equilibrationpolymerization conditions.polymerization conditions.
•• We use newer, more advanced catalysts, betterWe use newer, more advanced catalysts, bettersynthetic techniques.synthetic techniques.
Origin of Bleed...
•• Polymer SynthesisPolymer Synthesis
•• Oligomers that are “created” in a column’s lifetimeOligomers that are “created” in a column’s lifetime
Origin of Bleed...
•• Oligomers that are “created” in a column’s lifetimeOligomers that are “created” in a column’s lifetime
OSi Si
OSi
OSi
OSi Si
OH
SiO
Si
OH
(polymer coating)
PDMS
D3/D4 bleed
(FS tubing)
[ ]
Enhancement of Thermal Stability by Using“Additives”
Si O
CH3
CH3
OSi O
CH3
CH3
CH3
CH3
SiSix y z
SilphenyleneSilphenylene
Additives...
•• A column with true “One” selectivity cannot beA column with true “One” selectivity cannot beobtained by having silphenylene in the backbone.obtained by having silphenylene in the backbone.
Si O
CH3
CH3
nSi Si
CH3
CH3
CH3
CH3
Om
StxTM-1 HT
•• The polymer or the phase is PDMS.The polymer or the phase is PDMS.
n
C H 3
C H 3
OS i
Origin of Bleed...
fused silica
deactivation
Origin of Bleed...
fused silica
deactivation
Deactivation of the Fused Silica Surface
•• We are using an advanced deactivation calledWe are using an advanced deactivation calledSiltek™. It is a deposition process, unlike silazaneSiltek™. It is a deposition process, unlike silazaneor silicone deactivation.or silicone deactivation.
Aroclor® 1242
8 16 24
Aroclor® 1254
8 16 24
Aroclor® 1260
8 16 24
Aroclor® Run Conditions
Splitless Hold Time: 1.0min.Split Vent Flow: 40cc/min.Septa Purge: 5cc/min.Carrier Gas: HeliumHead Pressure: 8.5psiColumn Flow Rate: 1.9cc/min.Linear Velocity: 31cm/sec.Detector: ECD/310CMake up Gas Flow: 40cc/min.