Guide to Selection of a Capillary Column for GC

Reason for Capillary Column Selection

1. Stationary Phase

  • The least polar stationary phase among the columns that provides the desired separation shall be selected.
    *Almost 70% of the capillary GC analyses can be run in the stationary phase equal to 100% dimethyl- (BP1) or 5% phenyl-polysiloxane (BP5, BPX5).
  • The non-polar stationary phase separates compounds of similar structure by boiling point. Increasing the phenyl/cyanopropyl group content in the stationary phase significantly affects separation by dipole moment and localized electrons.
    [BP10(1701), BPX35, BPX50, BP225, BPX70]
  • A polyethylene glycol-type stationary phase is the best way to separate compounds with different hydrogen bonding forces (e.g. aldehydes, alcohols, ketones).
    [SolGel-WAX™, BP20(WAX), BP21(FFAP)]
<Effect of increasing the phenyl content of the stationary phase>
00939_img01.png
Columns:30 m x 0.25 mm x 0.25 µm
Initial Temp:45 ℃(1 min)
1st Temp Ramp:30 ℃/min to 200 ℃(0.1 min)
2nd Temp Ramp:7 ℃/min
Final Temp:315 ℃ (hold 10 min)
Injector Temp:280 ℃
Splitless Time :1 min
Carrier :He, 1 mL.min

Organophosphorus Pesticides

  1. 4-Chloro-3-nitrobenzotrifl uoride
  2. 1-Bromo-2-nitrobenzene
  3. Tributylphosphate
  4. Terbufos
  5. Dioxathion
  6. Phoshamidon
  7. Chlorfenvinphos
  8. Ethion
  9. Famphur
  10. Carbophenothion
  11. Triphenylphosphate
  12. Phosmet
  13. Leptophos
  14. Azinphos-ethyl

2. Internal Diameter

<Effect of Internal diameter on Polycyclic Aromatic Hydrocarbons (PAH) analysis>
00939_img02.png
  • The narrower the inner diameter of the column, the higher the column efficiency and the higher the resolution. If using a thin inner diameter column, the length of the column can be shortened, compared with the conventional column, and the analysis time can be shortened with equivalent separation. However, it is necessary to pay attention to the upper limit of the sample load.

3. Film Thickness

<Effect of film thickness>
00939_img03.png

Keeping similar phase ratios when changing column inner diameters for columns of the same type will give similar results without significant changes in chromatography parameters.
Film Thickness (µm) Internal diameter of the column (μm)
100 150 220 250 320 530
0.10 250 - 550 625 800 1325
0.15 - 250 - - - 883
0.25 - 150 220 250 320 530
0.50 - 75 110 125 160 265
1.00 - - 55 63 80 132
3.00 - - - - 27 44
5.00 - - - - 16 26
  • If the concentration range of each component in a sample is wide, a column with a thick film is recommended. By selecting a column with a thick film, leading of the peak of high concentration component due to the impact of overload or overlapping with other component peaks that should have been separated in a mixture of the same concentration may be prevented. If the separation of each component is sufficient to avoid the influence of a concentration difference, a column with a thinner film shall be selected, considering the peak shape.
  • The thicker the film, the longer the elution time, and the higher the elution temperature. In order to elute at the same retention time by doubling the film thickness in a thermostatic analysis, it is necessary to increase the oven temperature from 15°C to 20°C. The temperature program can be used to reduce the elution temperature slightly.
  • The phase ratio (β) is one of the parameters that shows suitability for various applications. A column with a low β value means a high ratio of film thickness relative to inner diameter, i.e., a strong retention force, suitable for volatile component analysis. On the other hand, a column with a high β value has a thin film and a relatively weak retention force, which is suitable for analysis of compounds with a large molecular weight and a high boiling point.

β = id/4df

β = phase ratio
id = internal diameter of the column (μm)
df = film thickness (μm)

<Scope of application by phase ratio>
Phase ratio (β) Application
16-100 gas, low M.W. hydrocarbons, solvents, Volatile halogen compounds (M.W.16-250)
100-320 semi-volatile compounds, common applications (M.W. 100-700)
320-1325 high M.W. hydrocarbons, wax, petroleum products (M.W. 300-1500)

When changing the inner diameter etc. of a column of the same type, a column with the same phase ratio can be selected to obtain a similar chromatogram.

4. Column Length

<Effect of column length>
00939_img04.png
  • The shortest column possible to achieve the required separation shall be selected. If a longer column cannot provide sufficient separation, it is necessary to examine the stationary phase and phase ratio again.
  • The resolution is proportional to the square root of the column length. When the column length is doubled, the resolution is basically improved by a factor of approximately 1.4.

Stationary Phase and Features of the SGE Capillary Column

Column Stationary phase Structural formula Features Use
BP1 100 % Dimethyl Polysiloxane 00939_img05.png
  • Standard chemical bond
  • 100 % Dimethyl Polysiloxane (Cross-linked type)
  • Excellent general purpose GC column
  • Low bleed
  • Non-polar stationary phase
  • All adapted for routine analysis
  • Maximum operating temperature: 320 ℃ / 340 ℃(Depends on film thickness)
Hydrocarbons, Aromatic compounds, Insecticides, Herbicides, Banned drugs, Phenols, Amine analysis
BP1 PONA 100 % Dimethyl Polysiloxane
  • Designed for petroleum product analysis. 
  • Non-polar stationary phase for PONA analysis
  • Suitable for distillation simulation ASTM (DHA-method).
  • Chemical bond (Cross-linked type)
  • Can be washed with solvent.
  • Maximum operating temperature: 320 ℃ / 340 ℃
Petroleum hydrocarbon, Gasoline hydrocarbon, MTBE, Paraffin, Olefins, Naphthenes, Aromatic compounds
BPX1 100 % Dimethyl Polysiloxane
  • Non-polar stationary phase
  • Structurally stable stationary phase
  • Low bleed
  • Designed specifically for high boiling hydrocarbon analysis.
  • Suitable for distillation simulation ASTM (DHA-method: D2887).
  • Maximum operating temperature: 430 ℃ (Aluminum clad column)
  • Maximum operating temperature: 370 ℃ / 400 ℃ (Polyimide clad column, Depends on film thickness)
ASTM method: D2887, D6532
SolGel-1ms™ 100 % Dimethyl Polysiloxane in a SolGel matrix
  • Ultra low bleed (Better MS library identification and sensitivity, reduced ion source maintenance frequency)
  • High inactivity 
  • Maximum operating temperature: 340 ℃ / 360 ℃
  • Can be used with all non-MS detectors.
  • Same selectivity as BP1
Ideal for analysis of highly active compounds.
BP5 5 % Phenyl / 95 % Dimethyl Polysiloxane 00939_img06.png
  • Excellent general purpose GC column
  • Low bleed
  • Slightly polar stationary phase
  • High heat resistance
  • Maximum operating temperature: 320 ℃ / 340 ℃(Depends on film thickness)
General analysis, Aromatic compounds, Insecticides, Herbicides, Drug, Hydrocarbon, Polychlorinated biphenyls, Essential oil, Semi-volatile compounds
HT5 5 % Phenyl Polycarborane-siloxane 00939_img07.png
  • High heat resistance
  • Unique stationary phase with no equivalent
  • Suitable for distillation simulation
  • Chemical bond (Cross-linked type)
  • Maximum operating temperature: 380 ℃ / 400 ℃(Polyimide clad column)
  • Can be washed with solvent.
Distillation simulation, Hydrocarbon, Insecticides, Herbicides
HT8 8 % Phenyl Polycarborane-siloxane
  • High heat resistance
  • Low bleed
  • Maximum operating temperature: 360 ℃ / 370 ℃
  • Ideal for PCB isomer analysis.
  • Stronger retention of low chlorine PCB isomers at ortho positions.
  • Suitable for environmental analysis by GC/MS.
  • Unique stationary phase suitable for analysis of POPs compounds
PCB analysis, Aromatic nitro compounds, Polycyclic aromatic compounds, Insecticides, Herbicides
BPX5 5 % Phenyl Polysilphenylene-siloxane 00939_img08.png
  • Highly inert
  • High heat resistance
  • Excellent general purpose GC column
  • Suitable for many daily analyses.
  • Ultra low bleed
  • Ideal for trace component analysis.
  • Ideal for GC/MS analysis.
  • Slightly polar stationary phase
  • Maximum operating temperature: 360 ℃ / 370 ℃(Depends on film thickness)
Ultra-trace component analysis, Insecticides, Herbicides, Hydrocarbon, Solvent, Phenols, Amines, Ideal for GC/MS and other GC analysis
BPX35 35 % Phenyl Polysilphenylene-siloxane
  • Medium polar stationary phase
  • Ideal for confirmatory analysis.
  • Inactive stationary phase
  • Equivalent to USP Phase G4.
  • High heat resistance and low bleed
  • Ideal for drug analysis.
  • Maximum operating temperature: 330 ℃ / 360 ℃
  • Ideal for GC/MS analysis.
  • Chemical bond (Cross-linked type)
  • Can be washed with solvent.
Environmental analysis, Insecticides, Herbicides, Banned drugs, Pharmaceuticals, Polycyclic aromatic compounds
BPX608 35 % Phenyl Polysilphenylene-siloxane
  • Ideal for ECD analysis.
  • Effective for analysis of organochlorine pesticides/herbicides.
  • Maximum operating temperature: 370 ℃
Environmental analysis, U.S. EPA method: 608, Insecticides, Herbicides
BPX50 50 % Phenyl Polysilphenylene-siloxane
  • Medium polar stationary phase
  • Inactive stationary phase
  • High heat resistance and low bleed
  • Suitable for USP EAP methods (Equivalent to G42)
  • Ideal for drug analysis.
  • Maximum operating temperature: 330 ℃ / 350 ℃ 
  • Chemical bond (Cross-linked type)
  • Can be washed with solvent.
U.S. EPA method: 604, 608, 8060, 8081, Triazine pesticides, Drug screening, Steroid, Pharmaceuticals, GC2D
BPX70 70 % Cyanopropyl Polysilophenylene Siloxane 00939_img09.png
  • High polar stationary phase
  • Inactive stationary phase
  • High heat resistance and low bleed
  • Ideal for analysis of fatty acid methyl esters (FAMEs).
  • Maximum operating temperature: 250 ℃ / 260 ℃
  • Chemical bond (Cross-linked type)
  • Can be washed with solvent.
Fatty acid methyl esters (FAMEs), Carbohydrate, Pharmaceuticals, GC/MS application
BPX90 90 % Cyanopropyl Polysilophenylene Siloxane
  • Unique chemical bond stationary phase
  • Extremely strong polar stationary phase
  • High heat resistance
  • Ideal for separating cis / trans isomers.
  • Ideal for analysis of fatty acid methyl esters (FAMEs).
  • Maximum operating temperature: 260 ℃ / 280 ℃
  • Can be washed with solvent.
Fragrance, Aromatic compounds, Petrochemicals, Insecticides, PCB, Fatty acid methyl esters (FAMEs), Trans fatty acids
SolGel-WAX™ Polyethylene Glycol (PEG) in a SolGel matrix 00939_img10.png
  • Bonded PEG stationary phase
  • High heat resistance
  • More resistant to oxygen damage than conventional WAX stationary phase.
  • High polar stationary phase
  • Ultra low bleed and highly inert
  • Maximum operating temperature: 280 ℃
  • Chemical bond (Cross-linked type)
  • Can be washed with solvent.
Ideal for analysis of highly active compounds
BP20(WAX) Polyethylene Glycol
  • Standard WAX column
  • High polar stationary phase
  • Maximum operating temperature: 240 ℃ / 280 ℃ (Depends on film thickness)
  • Chemical bond (Cross-linked type)
  • Can be washed with solvent.
Alcohols, Free acid, Fatty acid methyl esters (FAMEs), Aromatic compounds, Solvent, Essential oils
BP21(FFAP) Polyethylene Glycol (PEG) TPA treated
  • Modified PEG stationary phase with nitroterephthalic acid
  • High polar stationary phase
  • Ideal for analysis of low molecular weight organic acids.
  • Maximum operating temperature: 250 ℃
  • Chemical bond (Cross-linked type)
  • Can be washed with solvent (water and ethanol are not recommended).
Free acid, Fatty acid methyl esters (FAMEs), Alcohols, Aldehydes, Acrylates, Ketones
BP10(1701) 14 % Cyanopropylphenyl 86 % Dimethyl polysiloxane 00939_img09 (1).png
  • Ideal for analysis of organochlorine pesticides.
  • Medium polar stationary phase
  • Low bleed and high inert
Environmental analysis, US EPA method: 608, 8081, Insecticides, Herbicides, Abuse drugs, Pharmaceuticals
BPX-VOLATILES Cyanopropylphenyl Polysiloxane
  • Medium polar stationary phase
  • Suitable for US EPA volatile organic compound analysis (EPA 624, 502.2, SW-846, 8240/8260).
  • Chemical bond (Cross-linked type)
  • Maximum operating temperature: 290 ℃ / 300 ℃
  • Can be washed with solvent.
Environmental analysis, Volatile organic compounds, Alcohols, USP G43
BP624 Cyanopropylphenyl Polysiloxane
  • US EPA method: 624 corresponding column
  • Designed for volatile organic compound analysis.
  • Suitable for EPA 624, SW-846, 8240/8260.
  • Suitable for USP G43.
  • Maximum operating temperature: 230 ℃ / 300 ℃
  • Chemical bond (Cross-linked type)
  • Can be washed with solvent.
US EPA method: 624, Volatile organic compounds, chlorinated hydrocarbons, solvents in drinking water (EPA method: 501.3, 502.2, 503.1, 524.2, 601, 602, 8010, 8015, 8020, 8240, 8260)
CYDEX-B™ Permethyl-β-cyclodextrin (chiral)
  • For separating optical isomers
Separation of enantiomers in natural products

Correspondence Table for Each Compound and Capillary Column

◎: Stationary phase recommended for application
● : Stationary phase able to respond to application

Compounds SOLGEL-1ms BP1 BPX1 BP1-PONA BPX5 BP5 HT5 HT8 BPX35 BPX-Volatiles BP624 BP10 BPX50 SOLGEL- WAX BP20 BP21 BPX70 CYDEX-β BPX20
Acidic/Neulral Drugs                        
Acids                      
Alcohols                  
Amines Aliphatic                      
Amines Aromatic                    
Antidepressants                        
Aromatics - PAH                
Aroclors                        
Beverages - Alcohols                        
Butter - Fat                        
Chiral Compounds                          
Chlorinated Aromatics                    
Cigarette Lighter Fuel                        
Dioxins                        
Essential Oils                      
Food - FAME                    
Glucose - Methylated                        
Herbicides                    
Industrial Solvents                      
Ketones                    
Monomers                      
Nitroaromatics                
Organochlorine Pesticides                
Organophosphorous Pesticides                  
Paraffins                    
PCB's                      
Petroleum                    
Phenols                    
Phthalates                      
Plant Sterols                      
Polymers                        
Polywax                      
Pyrethroids                  
Racehorse Doping Mixture                        
Sedatives                        
Semivolatiles                      
Silicon Oil                          
Solvents                      
Sugars-Alditol Acetates                      
Triglycerides                        
TRPH                      
Volatiles                      
Xylenes                

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