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Copyrights: Restek Corporation
Column Selection“there is more to life than a boiling
point column”
Column Selection“there is more to life than a boiling
point column”
Jaap de Zeeuw
Restek Corporation,
The Netherlands
Copyrights: Restek Corporation
• Retention of a compound can be related to boiling point or solubility
• The solubility of a compound in the stationary phase is a better predictor of retention than boiling point..
Stationary Phase SelectivityBoiling Point versus SolubilityStationary Phase SelectivityBoiling Point versus Solubility
So.. what do we mean with “boiling point” separation columns and where are they used as such?
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2,3
1. acetone 56oC bp2. pentane 36oC3. propanol 97oC4. MEK 80oC5. hexane 69oC6. butanol 118oC7. 3-pentanone 101oC8. heptane 98oC9. pentanol 138oC10. octane 126oC
Run Conditions: Rtx-1
Dimensions: 30m, 0.32mm ID, 1.0 μm
Temperature: 70oC Isothermal
Carrier Gas: Helium at 20 cm/sec
Flow: 0.989 mL/min
Head Pressure : 5.91 psig
Injection: Split
Detector: FID
Rtx-1 100% polydimethyl siloxaneRtx-1 100% polydimethyl siloxane Alkanes
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2,3
1. acetone 56oC bp2. pentane 36oC3. propanol 97oC4. MEK 80oC5. hexane 69oC6. butanol 118oC7. 3-pentanone 101oC8. heptane 98oC9. pentanol 138oC10. octane 126oC
Run Conditions: Rtx-1
Dimensions: 30m, 0.32mm ID, 1.0 μm
Temperature: 70oC Isothermal
Carrier Gas: Helium at 20 cm/sec
Flow: 0.989 mL/min
Head Pressure : 5.91 psig
Injection: Split
Detector: FID
Rtx-1 100% polydimethyl siloxaneRtx-1 100% polydimethyl siloxane Ethers
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2,3
1. acetone 56oC bp2. pentane 36oC3. propanol 97oC4. MEK 80oC5. hexane 69oC6. butanol 118oC7. 3-pentanone 101oC8. heptane 98oC9. pentanol 138oC10. octane 126oC
Run Conditions: Rtx-1
Dimensions: 30m, 0.32mm ID, 1.0 μm
Temperature: 70oC Isothermal
Carrier Gas: Helium at 20 cm/sec
Flow: 0.989 mL/min
Head Pressure : 5.91 psig
Injection: Split
Detector: FID
Rtx-1 100% polydimethyl siloxaneRtx-1 100% polydimethyl siloxane Alcohols
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2,3
1. acetone 56oC bp2. pentane 36oC3. propanol 97oC4. MEK 80oC5. hexane 69oC6. butanol 118oC7. 3-pentanone 101oC8. heptane 98oC9. pentanol 138oC10. octane 126oC
Run Conditions: Rtx-1
Dimensions: 30m, 0.32mm ID, 1.0 μm
Temperature: 70oC Isothermal
Carrier Gas: Helium at 20 cm/sec
Flow: 0.989 mL/min
Head Pressure : 5.91 psig
Injection: Split
Detector: FID
Rtx-1 100% polydimethyl siloxaneRtx-1 100% polydimethyl siloxane
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Separation is according to boiling point …
Need to add something..
.. “within a certain class of compounds”..
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What about “polar” phases?
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Run Conditions: Stabilwax
Dimensions: 30m, 0.32mm ID, 1.0 μm
Temperature: 70oC Isothermal
Carrier Gas: Helium at 20 cm/sec
Flow: 0.989 mL/min
Head Pressure : 5.91 psig
Injection: Split
Detector: FID
2 35
1. pentane 36oC bp2. hexane 69oC 3. heptane 98oC 4. octane 126oC5. acetone 56oC 6. MEK 80oC7. 3-pentanone 101oC8. propanol 97oC 9. butanol 118oC 10. pentanol 138oC
PEG 100% poly ethylene glycolPEG 100% poly ethylene glycol
Polar phases also separate according to boiling point..Polar phases also separate according to boiling point..
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Where are “boiling point” separations used?Where are “boiling point” separations used?
Simulated Distillation
• Improved characterization of crude leads to better control of final product
• Increased gas oil yield
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Simulated DistillationSimulated Distillation
• Chromatographic procedure designed to mimic (simulate) the physical process of distilling petroleum products
• Establishes a FAST correlation between retention time and boiling point
• Results are used to control refining operations
• Results are also an indicator of the range of products that can be produced from a starting material and their potential yield
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1 2 3 4 5 6 7 8 9 10
Simulated Distillation Simulated Distillation
• The chromatogram of the sample is divided into time slices• The software determines the area count for each slice
• The chromatogram of the sample is divided into time slices• The software determines the area count for each slice
Retention time
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Retention Time vs Boiling Point Retention Time vs Boiling Point
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Simulated Distillation: ASTM methodsSimulated Distillation: ASTM methods
D2887 C6-C42 0.88 - 3 um PDMS 10/0.53 concentr.D7213 (2887-ext) C8-C60 0.15-1.2 um PDMS dilutedD3710 gasoline up to C14 2.65 um PDMS 10/0.53 concentr.D5307 crude up to C42 0.2 um PDMS, 5/0.53 dilutedD6352 C10-C90 0.1-0.2 um PDMS, 5/0.53 dilutedD7500 C7-C110 0.2 um PDMS, 5/0.53 dilutedD7169 C5-C100 0.2 um PDMS, 5/0.53 diluted
ASTM nr Range Column Injection
Methods can be classified by Boiling Point and Hydrocarbon rangesMethods can be classified by Boiling Point and Hydrocarbon ranges
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Challenges in Simulated DistillationChallenges in Simulated Distillation
• Columns Break (fused silica)
• Columns loose stationary phase by bleed• Need to do often calibrations (time)• Replace columns (price per analysis, time)• Reduced accuracy (reliability challenge)
• Columns are not efficient• Do not meet resolution requirements
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High temperature separations: column materialsHigh temperature separations: column materials
Aluminium coated Glass Capillary
MXT CapillaryHigh temperature Polyimide coated
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Problem with fused silica columns used for High temperaturesProblem with fused silica columns used for High temperaturesOperation at temperatures of 400ºC or higher will result in polyimide damage
• Column life time is dictated by the OUTSIDE coating;
• Column life time not predictable
• Coupling with PressTight connections is not possible
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Special High temperature polyimide was developed for highest temperature stability
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Better solutions MXT metal tubing: extreme strongBetter solutions MXT metal tubing: extreme strong
• Virtually unbreakable, self straightening
• Stable up to 450ºC
• Can be bended / coiled on small radius
• Stabilizes the stationary phase
• winded on standard column cages
For Simdist a MUST to use 0.53mm
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Bleed comparison using different surface deactivationsBleed comparison using different surface deactivations
Normal deactivation
Siltek-deac surface
SAME stationary phase,
DIFFERENT surface..
SAME stationary phase,
DIFFERENT surface..
Siltek coated surfaces bleed a factor 4-5 less
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• Silphenylene stabilized phases cannot be used for “simdist”separations
• The Sil-phenylene will provide some polarity, which causes deviations of calibration curve..
• Need to use 100% PDMS, to be able to use historical reference values.
• Stabilization done by increase of X-links in PDMS chain
Use of “Sil phenylene” phasesUse of “Sil phenylene” phases Si
CH3
CH3
O Si
CH3
CH3
O Si
CH3
CH3
X Y
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Simulated Distillation: ASTM methodsSimulated Distillation: ASTM methods
D2887 C6-C42 0.88 - 3 um PDMS 10/0.53 concentr.D3710 gasoline up to C14 2.65 um PDMS 10/0.53 concentr.D7213 (2887-ext) C8-C60 0.15-1.2 um PDMS dilutedD5307 crude up to C42 0.2 um PDMS, 5/0.53 dilutedD6352 C10-C90 0.1-0.2 um PDMS, 5/0.53 dilutedD7500 C7-C110 0.2 um PDMS, 5/0.53 dilutedD7169 C5-C100 0.2 um PDMS, 5/0.53 diluted
ASTM nr Range Column Injection
Methods can be classified by Boiling Point and Hydrocarbon rangesMethods can be classified by Boiling Point and Hydrocarbon ranges
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Column Performance-ASTM D7169Column Performance-ASTM D7169
Column : 5m x 0.53mm MXT Simdist, 0.1 μm Oven : 40°C → 430 °C, 1 min, 30°C/min
Column : 5m x 0.53mm MXT Simdist, 0.1 μm Oven : 40°C → 430 °C, 1 min, 30°C/min
C104
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Restek MXT columns show low bleed, because Silteksurface stabilizes the PDMS phaseRestek MXT columns show low bleed, because Silteksurface stabilizes the PDMS phase
Each column is tested with this test to guarantee performance..
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Oil spill Mississippi Canyon Block 252 Oil spill Mississippi Canyon Block 252
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Analysis of Tar balls/crudeAnalysis of Tar balls/crude
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Basic rule in GC stationary phase selection..Basic rule in GC stationary phase selection..
Solubility of sample component in the stationary phase based upon “likes dissolve likes.”
Solubility of sample component in the stationary phase based upon “likes dissolve likes.”
“ choose a stationary phase that “looks like” the components you want to separate..”
Hydrocarbons 100% PDMS type phase: Rtx-1
ASTM 6730: detailed hydrocarbon analysis;Many components (>500)
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GC-FID Hydrocarbons on Rtx-DHA-100GC-FID Hydrocarbons on Rtx-DHA-100C
3n-
Cn-
C
n-C
n-C
n-C
8
n-C
9
n-C
10
0 50 100 150
Column : 100 x 0.25 mm Rtx-DHA 100
Oven : 5°C, 10 min -> 50°C, 5°C/min, 54 min, --> 200°C, 1.3 °C/min
Carrier gas : He, 24 cm/s, 39.3 Psi; Injection Split, 1 : 150; Detection : FID;
Column : 100 x 0.25 mm Rtx-DHA 100
Oven : 5°C, 10 min -> 50°C, 5°C/min, 54 min, --> 200°C, 1.3 °C/min
Carrier gas : He, 24 cm/s, 39.3 Psi; Injection Split, 1 : 150; Detection : FID;
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Compensate by using Selective detection..Compensate by using Selective detection..
“Only see what I want to see”..MS-SIM, SClD/FPD/PFPD, AED, NPD, ECD, O-FID,..
• Can use non-polar columns, also shorter in length
• Efficiency / selectivity less important
Challenges:• Quenching / Bias
• Stability and Cost of ownership
• Need qualified people
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GC-MSGC-MS
In GC-MS 95% of the applications are done with a non-polar type stationary phases:
• 100% poly dimethyl siloxane (Rxi-1ms)• Arylene modified equivalent of 5% diphenyl /95%
dimethyl siloxane (Rxi-5ms and Rxi-5Sil MS)
If there is a co-elution, the MS will deconvolute if the mass spectra have clear different m/z fragments
If there is a co-elution, the MS will deconvolute if the mass spectra have clear different m/z fragments
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For the best quantitative result you need to optimize the separation first..
It s always better to quantify the individual analyte as matrix effects are eliminated
Selective detection is “nice” but we always have to think of the “possible” bias..
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2001 Las Vegas ISCC2001 Las Vegas ISCC
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Column SelectionColumn Selection
Back to Basics.. Rudi Kaiser
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When need Selectivity?When need Selectivity?• If there are limited nr of plates available;
• If components have to be separated by non-selective detection
• If components have same fragments in MS or cause a bias
• if selective detection is not “selective” enough..
• In multi dimensional separations
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Limited nr of Plates
When need Stationary Phase Selectivity?
When need Stationary Phase Selectivity?
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Limited number of platesLimited number of plates
Using packed columns.. 2000 -10.000 plates;
Lots of different stationary phases
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No deed for glass columns as metal is more inert due to Siltek deactivation
No deed for glass columns as metal is more inert due to Siltek deactivation
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If components have to be separated by non-selective detection
When need Stationary Phase Selectivity?
When need Stationary Phase Selectivity?
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Use of non selective detectorsUse of non selective detectors
FID is widely used: Cheap detector, but requires chromatographic separation
Column selectivity is very important: need to use tools available:
• Use literature search
• Use Chrom databases on the web from suppliers (Agilent, Restek, Sigma..)
• Use Chrom calculators and Optimization
Chrom calculators
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Example of Chromatogram CalculatorExample of Chromatogram Calculator
On-line EZ-GCChromatogram modeler
http://www.restek.com/chromatogram/ezgc/
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Shortest time analysis
Uses available databases
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Compound structure information + Physical constants
Compound structure information + Physical constants
Mass spectra dataMass spectra data
SynonymsSynonyms
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On-Line Method translator Flow calculatorOn-Line Method translator Flow calculator
Will also be a windows application
This will be available SOON.. Watch for the Restek news
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If components have same fragments in MS or cause a bias
When need Stationary Phase Selectivity?
When need Stationary Phase Selectivity?
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• When components are isobaric, and show similar mass spectra
• When component forms many similar ions (PCB, Dioxins, BFRs, PAH)
GC separation is essentialGC separation is essential
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Separation of PAH in foodSeparation of PAH in foodNIST SRM 2260a on 40m x 0.18mm x 0.07µm Rxi‐PAH
EPA
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PAH in Food: Chrysene-TriphenylenePAH in Food: Chrysene-Triphenylene
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PAH in Food: Benzo fluoranthenesPAH in Food: Benzo fluoranthenes
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Complex sample using GC/MSComplex sample using GC/MS
• Environmental method, TO-15• 70 components, 4 retentive phases
1-ms 5-ms5Sil MS VMS
Bias:-1ms : ethyl acetate and hexane overlap; share some of the same ions.-5ms/5SilMS : MEK and hexane overlap, share some of the same ions.
VMS separates all
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If Selectivity of Detector is not “selective “ enough..
When need Stationary Phase Selectivity?
When need Stationary Phase Selectivity?
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Selective DetectionSelective Detection
Is not always possible as “selectivity” has limitations.
“Only see what I want to see”..
Impurity in main product
If main component elutes together with Target analyte
Quenching:
signal of target is impacted by main analyte
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COS in propylene/propaneCOS in propylene/propaneFor trace sulfur, 100% PDMS is preferred.
On this phase COS elutes together with Propane/propylene
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0 2.5 5 7.5 100 2.5 5 7.5 100 2.5 5 7.5 100 2.5 5 7.5 10
Propylene elutes with propane on the Rt-UBOND
H2S
COS, 1 ppm
Expected position of ethylene
Need selective phase to separate COS from propylene/propaneNeed selective phase to separate COS from propylene/propane
propane
ethane
Polar Porous polymer, type „U“, 30m x 0.32mm ID x 10 μm Polar Porous polymer, type „U“, 30m x 0.32mm ID x 10 μm
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Multidimensional Separations
When need Stationary Phase Selectivity?
When need Stationary Phase Selectivity?
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Where else do I need selectivity?Where else do I need selectivity?
• If I do not get “enough” separation on my non-polar column..
• Very complex samples, need high peak capacity..
• Use column switching Valves
Deans (live)
Valves
Deans (live)
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Every major Instrument supplier offers a “flow”
switching solution
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Biodiesel fuel dilution in Lube oil by Flow Heart cut GCBiodiesel fuel dilution in Lube oil by Flow Heart cut GC
PDMS columnPDMS column
WAX columnWAX column
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Where else do I need selectivity?Where else do I need selectivity?
• If I do not get “enough” separation on my non-polar column..
• Very complex samples, need high peak capacity..
• Or use column switching
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GC x GC Enhanced peak capacityGC x GC Enhanced peak capacity
Peak capacity in GC xGC = 1000 x 30 = 30.000Peak capacity in GC xGC = 1000 x 30 = 30.000
To get equal peak capacity, we would need a 10 km column:
Analysis times > weeks
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Need to use “selectivity” to separate components that co-elute in the first dimension
Typical GC x GC SetupTypical GC x GC Setup
• Primary column (1st dimension)• Typical 30m x 0.25mm, film of 0.25-0.5um• Non-polar
• Modulator• Focuses effluent from primary column• “Injects” this effluent onto secondary column
• Secondary column (2nd dimension)• Typical 1-2m, 0.15-0.18mm, 0.15/0.18um• Polar or Selective
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Selectivities mostly usedSelectivities mostly used
First dimension: Non-Polar : Rxi-1ms, -5ms, -5Sil MSPolar : Rxi-17Sil MS
Second dimension: Liquid phases- Rxi-1ms- Rxi-5Sil MS- Rxi-XLB- Rxi-17Sil MS- Rtx-200- StabilWax- Cyano
Shape selective phases• Cyclodextrin modifications
• Liquid crystal
• Ionic Liquids
Major Challenge: temperature stability
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Nigerian Crude on GCxGC-TOF-MSNigerian Crude on GCxGC-TOF-MS
30m x 0.25mm x 0.25 μmnon-polar 5Sil MS
1.1m x 0.15 mm id. x 0.15 μm-17Sil-MS Range -60 - 360ºC
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Rxi-XLB
Rxi
-17S
il M
S
Rxi-17Sil MS
Rxi
-5m
s
Rtx
-1m
s
Rtx
-200
Rxi-5Sil MS
Rxi-17Sil MS
BFr’s en PCB’s
Hydrocarbon oils
cannabinoids
Terpenes cannabinoids
Pesticides
First column : non-polar
Second column : polar
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Rxi-XLB
Rxi
-17S
il M
S
Rxi-17Sil MS
Rxi
-5m
s
Rtx
-1m
s
Rtx
-200
Rxi-5Sil MS
Rxi-17Sil MS
BFr’s en PCB’s
Hydrocarbon oils
cannabinoids
Terpenes cannabinoids
Pesticides
First column : polar
Second column : non-polar
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Basic rule in GC stationary phase..Basic rule in GC stationary phase..
Solubility of sample component in the stationary phase based upon “likes dissolve likes.”
Solubility of sample component in the stationary phase based upon “likes dissolve likes.”
“ choose a stationary phase that “looks like” the components you want to separate..”
Hydrocarbons 100% PDMS Rtx-1
Aromatic subst. Phenyl subst. PDMS Rtx-5, 17Sil, 35Sil
Halogenates Arom. Fluorimated-phenyl Rtx-440, Cl-Pesticides, Rtx-200
Solvents Cyano /phenyl Rtx-1301/624Sil
Alcohols,diols,glycols PEG Stablewax/Rtx-wax
Double bonds Cyano propyl Rt 2330, 2460
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(GC-MS) Presence of Diethylene Glycol and Ethylene Glycol in Toothpaste (GC-MS) Presence of Diethylene Glycol and Ethylene Glycol in Toothpaste
Phase: PEG
Dissolves : ‘likes like”
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Important note on Selectivity behavior: It changes with temperature
Important note on Selectivity behavior: It changes with temperature
Liquid phases: By lower elution temperatures the phase behaves LESS polar
Solid phasesBy lower elution temperatures the phase behaves MORE polar
This effect is the biggest with POLAR stationary phases.. Peak elution can change..This effect is the biggest with POLAR stationary phases.. Peak elution can change..
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5 6 7
1-m Nap30 C/min
m8 10 12
10 C/min
5 C/min
7 min
12 min
19 min
2 C/min
1 C/min
0.5 C/min
33 min
50 min
72 min
Non-Polar phase: 100% PDMS column; different temperature programs: Analysis of a Naphtha mixtureNon-Polar phase: 100% PDMS column; different temperature programs: Analysis of a Naphtha mixture
Some components are very sensitive for changes in elution temperature..
Some components are very sensitive for changes in elution temperature..
155ºC
68ºC
81ºC
95ºC
115ºC
130ºC
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Medium polarity: Optimized phase for Cl-PesticidesPeak elution reversalMedium polarity: Optimized phase for Cl-PesticidesPeak elution reversal
At 8.9 psi, u = 22 cm/sAt 8.9 psi, u = 22 cm/s
At 26 psi, u = 61 cm/sAt 26 psi, u = 61 cm/s
Tel. = 250ºCTel. = 250ºC
Tel. = 210ºCTel. = 210ºC
4,4’-DDE
4,4’-DDE
Endosulfan I
Endosulfan I
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Polar column: TCEP Relative elution of benzene to C11 and C12 Polar column: TCEP Relative elution of benzene to C11 and C12
C12
C12
C12
C12
C12
C12
C11
C11
C11
C11
C11
Benzene
RI=1090
benzene
benzene
benzene
Benzene
RI = 1240
30ºC
50ºC
70ºC
90ºC
110ºC
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Temperature effect on selectivity using Al2O3/Na2SO4Temperature effect on selectivity using Al2O3/Na2SO4
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Impact of Flow rate on separation; Rt Alumina BOND / MAPDHigher flow = lower elution temperatureImpact of Flow rate on separation; Rt Alumina BOND / MAPDHigher flow = lower elution temperature
100kPa100kPa
200kPa200kPa
150kPa150kPa
acetylene
acetylene
acetylene
propadiene
propadiene
propadiene
C4
C4
C4
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Relative position of CO changes with temperatureRelative position of CO changes with temperature
40 ºC
80 ºC
120 ºC
CO
CO
CO
CH4
CH4
CH4
0.8 min
1.4 min
4 min
Column : 1m x 0.53mm MXT Molsieve 5A 80/100 mesh
Carrier : He, 180 kpa
Split : 1 : 30; Injection: 15 μl; Sample: 2-5% in He
Detection : micro-TCD
Column : 1m x 0.53mm MXT Molsieve 5A 80/100 mesh
Carrier : He, 180 kpa
Split : 1 : 30; Injection: 15 μl; Sample: 2-5% in He
Detection : micro-TCD
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Summary Summary
A boiling point column will only separate according to boiling point if the same class of compounds are considered
Columns with different selectivity’s will be essential for running many applications even using selective detection systems
Choosing selectivity will remain a challenge as we depend on data. More tools will be developed in future to help us.
Additional, selectivity is temperature dependent which means there is another factor that plays a role.
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If you want to learn Chromatography?If you want to learn Chromatography?Visit the Restek ChromaBLOGraphy..A LOT of information shared by Restek scientists that allow you to
get better in your chromatography.. www.restek.com
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Use the Search option..Use the Search option..
If you want to know about: “what do chromatograms tell us?”
Just search on “ what do chromatograms..” and you can get a full list with links..
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Thanks you for participating
If your any question, please drop me an email
Jaap.deZeeuw@Restek.com
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