RestekCorporation
(800) 356-1688
1
23 4 5 6 7 8
9
10 11
12
13
14
15 16 17
18
20
0
10
30
min.
1. pentane
2. hexane
3. heptane
4. octane
5. nonane
6. decane
7. undecane
8. dodecane
9. tetradecane
10. hexadecane
11. octadecane
12. eicosane
13. tetracosane
14. octacosane
15. dotricontane
16. hexatricontane
17. tetracontane
18. tetratetracontane
Column:
25" x
1
/
8
"ODx2mm ID, Rtx
®
-1SimDist 2887
Silcosteel
®
packed column (cat.#80000). 1.0µl direct injectionof
D2887CalibrationMix (cat.#31222).
Oven temp.:
35°C to350°C
@10°C/min. (hold5min.);
Inj./ det. temp.:
350°C;
Carrier gas:
helium@25ml/min.;
FID sensitivity:
256x10
-11
AFS.
and reproduciblebaselineswith just 30
minutes of conditioning. This results in
fewer baselineblanks and less frequent
calibration increasing laboratory
productivity.
Rtx
®
-1SimDist 2887PackedCol-
umns canalsobeused for gasoline
range simulateddistillation.
Simulateddistillationof gasoline range
hydrocarbons according toASTM
methodD3710-93 can alsobeper-
formedusing theRtx
®
-1SimDist 2887
PackedColumn.
Figure 2
shows the
analysis ofASTMD3710 calibration
mixwith the additionof n-propane, 2-
methyl propane, n-butane, n-
hexadecane, andn-heptadecane.To
achievebaseline separationof n-
propane, 2-methyl propane, andn-
butane, theGCovenwas cooled to
-30°Cwith liquidnitrogen.
Figure3
shows the analysis of a composite
gasoline sampleunder the same run
conditions.Other volatilepetroleum
fractions such as kerosene and jet fuel
can alsobe analyzedwith this column.
Bonded stationary phases extend
column lifetime.
TheRtx
®
-1 stationaryphase is bonded
to the diatomite particles resulting in an
immobilized coatingwhich is resistant
to solvents and lower inbleed than
conventional packing. Since thepacking
is preconditioned, there is noneed for
extendedconditioning.Extended
conditioning cangreatlydecrease
column lifetime. SinceGC systems
oftenhave leaks or carrier gas that
contains oxygen, it ismore likely that
conventional columnswill bedamaged
during the conditioningprocess.
Figure
4a
shows a conventionalUCW-982
column after only170 temperature
cycles, demonstratinghigher bleed and
more tailing than theRtx
®
-1SimDist
column (
Figure4b
).Although actual
column lifetimes dependupon the
system and typeof samples analyzed,
thebonded stationaryphase should
result in longer lifetime than its non-
bondedequivalent.
Rtx
®
-1SimDist columns have
equivalent polarity toOV-101and
UCW-982.
Inorder for a stationaryphase tobe
acceptable forASTMmethods, the
columnmust not exhibit selective
retention for aromatichydrocarbons
compared toaliphatichydrocarbons.
This is an important test because if the
polarityof a column is different, the
boilingpoint resultswill demonstrate a
bias, especially for highly aromatic
samples.The “polarity”of thebonded
Rtx
®
-1 columnwas comparedwithOV-
101 andUCW-982, twoof themost
common stationaryphases currently
used for simulateddistillation. The
results of the calculatedboilingpoints
for aromatics compared to thepublished
boilingpoints appear inTable II.All
three silicone columns tested are
essentially identical in they elute
aromatics at a slightly lower tempera-
ture than the alkanes. This confirms the
polarityof theRtx
®
-1 column is
equivalent, and theboiling rangevalues
obtainedwill agreewithOV-101 and
UCW-982columns.
Rtx
®
-1 is an excellent choice forSim
Dist usingpacked columns.
Simulateddistillation is one of themost
commonGC analyses performed in the
petroleum laboratory.ASTM test
methodsD2887 andD3710 canbe
performedwith either packedor
capillary columns, but until now the
benefits of bondedphaseswere
availableonly to capillaryusers. The
Rtx
®
-1packed columnuses abonded
stationaryphasewhich is immobilized
onSilcoport
™
-a speciallydeactivated
support.The columns areprepared
usingSilcosteel
®
tubing for inertness
unavailablewith conventionalmetal
tubing.Rtx
®
-1bondedpacked columns
requireminimal conditioning andgive
stablebaselines and retention even after
only30minutes of operation at 350°C.
If your laboratoryhas been looking for
a betterSimDist analysis,Restek’sRtx
®
-
1packed columns are the answer.
Figure 1
C5 toC44 calibrationanalysis after only30minutes conditioning.
