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15
GC COLUMNS
Selecting a GC Column
95%
5%
CH
3
CH
3
Si
O
O
CH
3
CH
3
Si
CH
3
CH
3
Si
Structures, Polarities, Properties, and Uses for Restek® Capillary Column Phases, in Order of Increasing Polarity
Similar to: (100%-methyl)-polysiloxane
Polarity: nonpolar
Uses:
solvents, petroleum products,
pharmaceutical samples, waxes
Similar to: (5%-phenyl)-methylpolysiloxane
Polarity: slightly polar
Uses:
flavors, environmental,
aromatic hydrocarbons
CH
3
CH
3
Si
100%
O
CH
3
CH
3
Si
95%
O
Si
5%
O
CH
3
CH
3
Si
80%
O
Si
20%
O
Rtx
®
-20
Diphenyl dimethyl polysiloxane
Rxi®-1ms,
Rxi®-1HT, Rtx
®
-1
Dimethyl polysiloxane
Rxi®-5ms, Rxi®-5HT,
Rtx
®
-5, Rtx®-5MS
Diphenyl dimethyl polysiloxane
Similar to: (20%-phenyl)-methylpolysiloxane
Polarity: slightly polar
Uses:
volatile compounds, alcohols
[G1]
[G27]
[G28] [G32]
note
Structures, polarities, and properties also apply
to metal MXT® stationary phases.
Similar to: (5%-phenyl)-methylpolysiloxane
Polarity: slightly polar
Uses:
flavors, environmental, pesticides,
PCBs, aromatic hydrocarbons
Rxi®-5Sil MS
1,4-bis(dimethylsiloxy)phenylene
dimethyl polysiloxane
Polarity: polar
Uses:
FAMEs, flavors, acids, amines, solvents, xylene isomers
H
H
C C O
H
H
Stabilwax®, Rtx®-Wax,
Stabilwax®-MS
Polyethylene glycol
[G14] [G15] [G16] [G20] [G39]
Rtx
®
-1701
Cyanopropylmethyl phenylmethyl polysiloxane
Rtx®-65, Rtx
®
-65TG
Diphenyl dimethyl polysiloxane
(CH
2
)
3
Si
C N
90%
O
(CH
2
)
3
C N
(CH
2
)
3
Si
C N
10%
O
Rtx
®
-225
Cyanopropylmethyl phenylmethyl
polysiloxane
Rtx®-2330
Biscyanopropyl cyanopropylphenyl polysiloxane
x
y
Si
O
(CH
2
)
3
CH
3
Si
O
CH
3
z
CH
3
CH
3
Si
O
C N
Similar to: (14%-cyanopropylphenyl)-methylpolysiloxane
Polarity: intermediately polar
Uses:
pesticides, PCBs, alcohols, oxygenates
[G46]
Similar to: (65%-phenyl)-methylpolysiloxane
Polarity: intermediately polar
Uses:
triglycerides, rosin acids, free fatty acids
CH
3
CH
3
Si
35%
O
Si
65%
O
CH
3
(CH
2
)
3
CH
3
Si
50%
O
Si
C N
50%
O
Similar to: (50%-cyanopropylmethyl)-
methylphenylpolysiloxane
Polarity: polar
Uses:
FAMEs, carbohydrates
[G7] [G19]
Similar to: (95%-cyanopropyl)-phenyl polysiloxane
Polarity: polar
Uses:
cis/trans
FAMEs, dioxin isomers, rosin acids
[G8] [G48]
Rtx
®
-1301, Rtx®-624,
Rtx®-G43
Cyanopropylmethyl phenylmethyl polysiloxane
x
y
Si
O
(CH
2
)
3
CH
3
Si
O
CH
3
z
CH
3
CH
3
Si
O
C N
Similar to: (6%-cyanopropylphenyl)-
methylpolysiloxane
Polarity: intermediately polar
Uses:
volatile compounds, insecticides
[G43]
CH
3
CH
3
Si
65%
O
Si
35%
O
Rtx
®
-35
Diphenyl dimethyl polysiloxane
Similar to: (35%-phenyl)-methylpolysiloxane
Polarity: intermediately polar
Uses:
pesticides, PCBs, amines,
nitrogen-containing herbicides
[G42]
x
Si
O
65%
CH
3
CH
3
Si
O
y
R
O
CH
3
CH
3
Si
CH
3
CH
3
Si
Rxi
®
-35Sil MS
Rxi®-624Sil MS
x
Si
O
(CH
2
)
3
CH
3
CH
3
CH
3
Si
O
R
O
CH
3
CH
3
Si
94%
y
CH
3
CH
3
Si
C N
Similar to: (6%-cyanopropylphenyl)-
methylpolysiloxane
Polarity: intermediately polar
Uses:
volatile compounds, insecticides, residue
solvents in pharmaceutical products
Similar to: (35%-phenyl)-methylpolysiloxane
Polarity: intermediately polar
Uses:
pesticides, PCBs, amines,
nitrogen-containing herbicides
Rxi
®
-17
Diphenyl dimethyl polysiloxane
Rxi
®
-17Sil MS
Rtx
®
-200
Trifluoropropylmethyl polysiloxane
Similar to: (50%-phenyl)-methylpolysiloxane
Polarity: intermediately polar
Uses:
triglycerides, phthalate
esters, steroids, phenols
[G3]
CH
3
CF
3
(CH
2
)
2
Si
O
Similar to: (trifluoropropyl)-methylpolysiloxane
Polarity: selective for lone pair electrons
Uses:
environmental, solvents, Freon® gases,
drugs, ketones, alcohols
[G6]
CH
3
CH
3
Si
50%
O
Si
50%
O
x
Si
O
50%
CH
3
CH
3
Si
O
y
R
O
CH
3
CH
3
Si
CH
3
CH
3
Si
CH
3
Si
100%
O
Rtx®-50
Phenyl methyl polysiloxane
Similar to: (50%-phenyl)-methylpolysiloxane
Polarity: intermediately polar
Uses:
FAMEs, carbohydrates
[G3]
Similar to: (50%-phenyl)-methylpolysiloxane
Polarity: intermediately polar
Uses:
triglycerides, phthalate
esters, steroids, phenols
[G36]
[G2] [G38]
[G3]
[G17]