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Stable Flow Ensures Predictable
Retention Times
To demonstrate the superior stability of
MXT® PLOT columns, an MXT®-Q-BOND col-
umn and a competitor’s Q type column were
subjected to 240 pressure pulse cycles and
the spiking observed in each analytical run
was used as an indicator of particle genera-
tion, or phase instability. Results demon-
strate that particle generation on the Varian
column was significantly higher (Figure 2),
resulting in restrictions in the column that
caused a shift in retention time (Figure 3). In
contrast, the MXT®-Q-BOND column showed
little spiking. Greater phase stability resulted
in consistent flow behavior and predictable
retention times (Figure 4).
Key Phases Available for
Optimized Separations
New metal MXT® columns are available for
all major adsorbent types: porous poly-
mer, molecular sieve, and alumina. Porous
polymer MXT® columns, such as the MXT®-
Q-BOND column, are highly inert and effec-
tive at separating both polar and nonpolar
compounds. Volatiles are strongly retained,
making these columns extremely useful for
determining solvents. Molecular sieve col-
umns provide efficient separation of argon
and oxygen, as well as other permanent
gases. Metal MXT® alumina columns are rec-
ommended for light hydrocarbon analysis, as
alumina is one of the most selective adsor-
bents available and allows all C1-C5 isomers
to be separated with the highest degree of
resolution.
Summary
MXT® PLOT columns from Restek offer
greater stability than conventional PLOT col-
umns, making them a better choice for pro-
cess monitoring. New bonding techniques
produce columns with highly reproducible
flow characteristics, improved layer stabil-
ity, and excellent separation efficiencies.
These robust columns produce exceptionally
reproducible chromatography, providing the
reliable performance needed for process GC
analyzer applications.
For the complete version of this technical
article, visit
Figure 3: A conventional PLOT column releases particles following pressure pulsing,
forming restrictions in the column that affect flow behavior and change retention time.
Isothermal testing before and after 240 pressure pulse cycles. Column: Varian Q type PLOT, 25 m x 0.53 mm ID; Sample: solvent mix; Injec-
tion: 1 µL split, 250 °C; Split vent flow rate: 150 mL/min.; Oven: 150 °C; Carrier gas: hydrogen, constant pressure (4 psi, 27.6 kPa); Detector:
FID@ 250 °C.
Figure 4: MXT® PLOT columns are exceptionally stable; flow characteristics and reten-
tion times are highly consistent and not affected by pressure pulses.
Isothermal testing before and after 240 pressure pulse cycles. Column: MXT®-Q-BOND PLOT, 30 m x 0.53 mm ID x 20 µm (cat.# 79716);
Sample: solvent mix; Injection: 1 µL split, 250 °C; Split vent flow rate: 150 mL/min.; Oven: 150 °C; Carrier gas: hydrogen, constant pressure
(4 psi, 27.6 kPa); Detector: FID@ 250 °C.
GC_PC1185
Peaks
1. Methane
2. Methanol
3. Ethanol
4. Acetone
5. Diethylether
6. Ethyl acetate
7. Hexane
Retention times are stable on
MXT®-Q-BOND columns.
GC_PC1186
Peaks
1. Methane
2. Methanol
3. Ethanol
4. Acetone
5. Diethylether
6. Ethyl acetate
7. Hexane
MXT®-Q-BOND Columns
(Siltek®-treated stainless steel PLOT)
3.5" coil 7" 11-pin cage 3.5" coil 7" 11-pin cage
ID df temp. limits 15-Meter 15-Meter 30-Meter 30-Meter
0.25mm 8µm to 280/300°C 79718-273 79718
0.53mm 20µm to 280/300°C 79716-273 79716
Other phases available, visit for details.
Before
After 240 pressure pulse programs