GC columns Selection

Stationnary Phase

Choosing a stationary phase is the most important step in selecting a column.
Select the least polar phase that will perform the separation you require.
Synonymous use of the terms polarity and selectivity is not accurate, but it is very common.
Selectivity is determined by the physicochemical interactions of the solute molecules with the stationary phase. Polarity is determined by the structure of the stationary phase. Polarity does have an effect on separation; however, it is only one of the many stationary phase properties that influence peak separation.
Selectivity can be thought of as the ability of the stationary phase to differentiate between two solute molecules by differences in their chemical or physical properties. Separation is obtained if the interactions between the stationary phase and solutes are different.
For liquid or gum stationary phase (polysiloxanes and polyethylene glycols), there are three major interactions: dispersion, dipole, and hydrogen bonding. The following is a simplified and condensed explanation of the interactions for polysiloxane and polyethylene glycol stationary phases.

GC Columns Stationary Phase Applications Guide
 
Application Composition Polarity   Approximate Temp Range (°C) Similar Phases
Amines, hydrocarbons, pesticides, PCBs, phenols, sulfur compounds, flavors and fragrances 100% Dimethylpolysiloxane Non-polar   From -60
to 325/350		 UptiBond-1P, HP-1ms, DB-1ms, HP-1, DB-1, BP-1, SPB-1, CP-Sil 5, Rtx-1, OV-1, SE-30, 007-1, ZB-1
Semivolatiles, alkaloids, drugs, FAMEs, halogenated compounds, pesticides, herbicides 5% Phenyl 95% dimethylpolysiloxane Non-polar   From -60
to 325/350		 UptiBond 5P, HP-5ms, DB-5, HP-5, SPB-5, XTI-5, Mtx-5, CP-Sil 8CB, SE-54, Rtx-5, BPX-5, MDN-5, Rtx-5ms, BP-5, ZB-5
Semivolatiles, alkaloids, drugs, FAMEs, halogenated compounds, pesticides, herbicides 5% Phenyl 95% dimethylpolysiloxane Non-polar   From -60
to 325/350		 DB-5ms, Rtx-5ms, Rtx-5Sil MS, Rxi-5ms, Rxi-5Sil MS, VF-5ms, PTE-5, CP-Sil 8 CB Low Bleed/MS, BPX-5, AT-5ms, ZB-5ms, SLB-5ms, Equity-5
Aroclors, alcohols, pesticides, VOCs 6% Cyanopropyl-phenyl 94% dimethylpolysiloxane Mid-polar   From -20
to 280/300		 UptiBond 1301, DB-1301, Rtx-1301, PE-1301, VF-1301ms
 
CLP-pesticides, aroclors, pharmaceuticals, drugs of abuse 35% Phenyl 65% dimethylpolysiloxane Mid-polar   From 40
to 300/320		 DB-35, HP-35, Rtx-35, SPB-35, AT-35, Sup-Herb, MDN-35, BPX-35
CLP-pesticides, aroclors, pharmaceuticals, drugs of abuse 35% Phenyl 65% dimethyl arylene siloxane Mid-polar   From 50
to 340/360		 DB-35ms, Rtx-35, Rtx-35ms, VF-35ms, SPB-35, AT-35, Sup-Herb, MDN-35, BPX-35
   
Pesticides, herbicides, TMS sugars, aroclors 14% Cyanopropyl-phenyl 86% dimethylpolysiloxane Mid-polar   From -20
to 280/300		 UptiBond 1701, DB-1701, DB-1701P, SPB-1701, CP-Sil 19 CB, Rtx-1701, CB-1701, OV-1701, 007-1701, BPX-10
Drugs, glycols, pesticides, steroids 50% Phenyl 50% dimethylpolysiloxane Mid-polar   From 40
to 280/300		 UptiBond 17, HP-50+, DB-17, Rtx-50, CP-Sil 19 CB, BPX-50, SP-2250
Drugs, glycols, pesticides, steroids 50% Phenyl 50% dimethyl arylene siloxane Mid-polar   From 40
to 320/340		 DB-17ms, HP-50+, Rtx-50, VF-17ms, 007-17, SP-2250, SPB-50, BPX-50, SPB-17, AT-50
Residual solvents, pesticides, herbicides 35% Trifluoropropyl 65% dimethylpolysiloxane Polar   From 30
to 300/320		 DB-200 , Rtx-200, VF-200ms
EPA Methods 8140 and 609 50% Trifluoropropyl 50% dimethylpolysiloxane Polar   From 45
to 240/260		 UptiBond 210, DB-210, SP-2401
FAMEs, alditol acetates, neutral sterols 50% Cyanopropyl-phenyl 50% dimethylpolysiloxane Polar   From 40
to 220/240		 UptiBond 225, DB-225ms, DB-225, SP-2330, CP-Sil 43 CB, OV-225, Rtx-225, BP-225, 007-225
 
Alcohols, free organic acids, solvents, essential oils, flavors and fragrances Polyethylene glycol Polar   From 40
to 260/270		 HP-INNOWax, HP-20M, SUPELCOWAX 10, CP-WAX 52 CB, SUPEROX II, CB-WAX, Stabilwax, BP-20, 007-CW, Carbowax, DB-WAXetr, ZB-WAX
Solvents, glycols, alcohols Polyethylene glycol Polar   From 20
to 250/260		 UptiBond WAX, DB-WAX, HP-20M, SUPELCOWAX 10, CP-WAX 52 CB, SUPEROX II, CB-WAX, Stabilwax, BP-20, 007-CW, Carbowax, HP-INNOWax, Rtx-WAX, ZB-WAX, VF-WAXms
Amines, basic compounds Polyethylene glycol-base modified Polar   From 60
to 220/240		 UptiBond Amine, CAM, Stabilwax-DB, Carbowax Amine
Organic acids, alcohols, aldehydes, ketones, acrylates Polyethylene glycol-acid modified Polar   From 40
to 250		 UptiBond FFAP, HP-FFAP, DB-FFAP, OV-351, SP-1000, Stabilwax-DA, 007-FFAP, Nukol
FAMEs (requiring cis/trans resolution) 50% Cyanopropyl 50% dimethylpolysiloxane Polar   From 40
to 250/260		 DB-23, SP-2330, Rtx-2330, 007-23, AT-Silar, BPX-70, SP-2340, VF-23ms
Chiral compounds (general purpose) 30%-heptakis (2,3-di-O-methyl-6-O-t-butyl dimethylsilyl)-B-cyclodextrin in DB-1701 Mid-polar   From 35
to 260/280		 CycloSil-ß, LIPODEX C, Rt-ß DEXm, ß-DEX 110, ß-DEX 120
Chiral compounds (using a Nitrogen selective detector, NPD) beta-Cyclodextrin in phenylbased stationary phase Mid-polar   From 30
to 240/250		 HP-Chiral ß, LIPODEX C, Rt-ß DEXm, ß-DEX 110, ß-DEX 120
Permanent and noble gases. Argon and oxygen separation at 35°C 5Å molecular sieve zeolite     From -60
to 300		 HP-PLOT Molesieve
C1-C6 hydrocarbons in natural gas, refinery gas, fuel gas, synthetic gas, dienes Aluminum Oxide KCl deactivated Least polar   From -60
to 200		 HP-PLOT Al2O3 KCl, CP-Al2O3/KCl PLOT, Rt-Alumina PLOT, Alumina PLOT, Al2O3/KCl
C1-C6 hydrocarbons in natural gas, refinery gas, fuel gas, synthetic gas, dienes Aluminum Oxide "Sodium Sulfate" deactivated Mid-polar   From -60
to 200		 HP-PLOT Al2O3 S, CP-Al2O3 PLOT Na2SO4
C1-C6 hydrocarbons in natural gas, refinery gas, fuel gas, synthetic gas, dienes Aluminum Oxide with proprietary deactivation Most polar   From -60
to 200		 GS-Alumina, Al2O3/KCl, Al2O3/Na2SO4, Rt-Alumina PLOT, Alumina PLOT
Hydrocarbons including isomers, CO2, methane, air/CO, water, polar solvents, sulfur compounds Polystyrene-divinylbenzene     From -60
to 270/290		 HP-PLOT Q, CP PoraPLOT Q, CP PoraPLOT Q-HT, Rt-QPLOT, SupelQ PLOT, GS-Q
C1-C7 hydrocarbons, CO2, methane, air/CO, water, oxygenates, amines, solvents, alcohols, ketones, aldehydes Divinylbenzene/ethylene glycol dimethacrylate     From -60
to 19		 HP-PLOT U, PoraPlot U, RTU PLOT
C1-C12 hydrocarbons, CO2, trace-level sulfurs, hydride gases, inorganic gases, halocarbons, SF6, oxygen/nitrogen separation at -80°C Proprietary, bonded silica-based     From -80
to 260/300		 GS-GasPro, CP-Silica PLOT
Oxygenates Proprietary phase, high selectivity     To 350 GS-OxyPLOT, CP-LowOX
C1-C5 hydrocarbons, CO2, air/CO, trace acetylene in ethylene, methane Bonded monolithic carbon layer     From 0
to 360		 GS-CarbonPLOT, Carbopack, CLOT, Carboxen-1006 PLOT, CP-CarboPLOT P7
European Commission regulated polycyclic aromatic hydrocarbons Proprietary phase Mid-polar   From 40
to 320/340		 DB-EUPAH
Volatile Priority Pollutants, EPA Method 502.2 6% Cyanopropyl-phenyl, 94% dimethylpolysiloxane Mid-polar   From -20
to 260		 UptiBond 624, DB-624, AT-624, Rtx-624, PE-624, 007-624, 007-502, CP-624, ZB-624, VF-624ms
Volatile Organic Compounds using MSD, ELCD/PID Proprietary phase Non-polar   From -10
to 260		 DB-VRX, VOCOL, NON-PAKD, Rtx-Volatiles, PE-Volatiles, 007-624, HP-624, CP-624, Rtx-VRX, Rtx-VGC
CLP Pesticides, Chlorinated Herbicides, PCBs, 508.1 Pesticides 35% Phenyl, 65% dimethyl arylene siloxane Mid-polar   From 50
to 340/360		 DB-35ms, Rtx-35, Rtx-35ms, VF-35ms, SPB-35, AT-35, Sup-Herb, MDN-35, BPX-35

 Stationary Phase Interactions

Functional Group Dispersion Dipole Hydrogen Bonding
Methyl Strong None None
Pheny Strong None to Weak Weak
Cyanopropyl Strong Very Strong Moderate
Trifluoropropyl Strong Moderate Weak
PEG Strong Strong Moderate

 

Column length in meters (m)
Always try to select the shortest column length that will provide the required resolution for the application.
If the maximum column length available is being used, and resolution of the sample mixture is still inadequate then try changing the stationary phase or internal diameter
The resolution is proportional to the square root of the column efficiency. Therefore, doubling the column length will only increase the resolving power of the column by approximately 40%.
   
Inner diameter (ID) or internal diameter in millimeters (mm)
The smaller the diameter the greater the efficiency, hence better resolution
Fast column (0.1mm) are used for faster analysis because the same resolution can be achieved un a shorter time.
   
Film thickness in micrometers (µm)
For samples with a variation in solute concentration, a thicker film column is recommended. This will reduce the possibility of broad overloaded peaks co-eluting with other compounds of interest. If the separation of two solutes is sufficient and co-elution is still unlikely, even with large differences in concentration; then a thinner film can be used.
The greater the film thickness the greater the retention of solutes, therefore the higher the elution temperature
As a rule, doubling the film thickness results in an increase in elution temperature of approximately 15-20° under isothermal conditions. Using a temperature program, the increase in elution temperature is slightly less.