Universal Angled Press-Tight
®
Connectors
Siltek
®
-treatedUniversal Angled Press-Tight
®
Connectors
•
9
•
800-356-1688 •
2005vol. 3
MethodD-6730-01 suggests usinghelium as the carrier gas, at a linear veloc-
ity of 24cm/sec. (approximately 2.3mL/min.). The tridecane (C13) retention
time this combination yields, approximately 146minutes, greatly limits sam-
ple throughputperday.OurenhancedRtx®-1PONAcolumnmeetsorexceeds
all criteria in themethod,butdoes so in30% less time: retention time forC13
is 97minutes,usinghelium as the carrier gas.¹ Inmost applications hydrogen
is a better alternative to helium as the carrier gas, because it can be used at
muchhigher linear velocitieswithout compromising critical resolutions.
A revision to ASTMD 6730-01 proposed by Neil Johansen Inc. (Aztec, New
Mexico), in association with Envantage Analytical Software Inc. (Cleveland,
Ohio),has establishedoptimalDHAX (detailedhydrocarbonanalysis—extend-
ed) parameters, including specifying hydrogen as the carrier gas. Using these
conditions, analysis time is reduced towithin71minutes (C13)—a53% reduc-
tion versus using helium as the carrier gas. The method also is extended to
includemiddledistillateshaving finalboilingpointsup to509°C/948°F(
n
-C38).
Restek providedNeil Johansen Inc. with an enhanced Rtx®-1PONA column
(100m x 0.25mm ID x 0.5µm df) and an Rtx® 5PONA tuning column for
DHAXmethod development. The Rtx®-1PONA columnwas connected to 3
meters of the tuning column through a Universal Angled Press-Tight®
Connector (cat.# 20446) andwas installed in a PerkinElmer AutoSystemXL
GC equippedwith a flame ionizationdetector andprogrammablepneumatic
control. The data system used was ChromPerfect Spirit (Justice Laboratory
Software, Denville, NJ). Individual compounds were identified by using
Dragon- DHA software, developed by Envantage Analytical Software Inc. in
association withNeil Johansen Inc., which uses algorithms to process high-
resolution chromatographic data. Processed data for the PONAVI reference
standard, containingmore than 400 individual components of finished gaso-
line, canbe reviewedon theRestekwebsite:www.restek.com/PONA
The proposedDHAXmethodwas optimized with hydrogen carrier gas at a
rate of 3.62mL/min, constant flow, producing a linear velocity of 55cm/sec.
ThenewRtx®-1PONAcolumnwas conditioned in less than twohours, as fol-
lows: 35°C for 15min., to 300°C at 10°C/min., hold 30min., cool to 35°C.
Dead timewasadjusted toelutemethaneat3.50±0.05min., thenaDHA/oxy-
genates setup blend was introduced into the column to determine the col-
umn’s suitability for themethod.
Figure1A lists themeasuredcritical criteria.Onceestablished that thecolumn
met themethod criteria,GCovenprogramparameterswere entered and trial
injections of theDHA/oxygenates setup blendwere begun. The analysis was
permitted to run until
n
-C13was eluted. Based on the resolutions achieved,
the length of the tuning column was reduced incrementally until all critical
pairsmetD-6730-01 specifications. In this exampleapplication, theappropri-
ate tuning column length was 2.36 meters. Figure 1B indicates the critical
pairs. The full analysis of the 400-plus component PONAVI reference stan-
dard, listing retention indices (RIs) calculatedusingDragon-DHA software, is
postedon theRestekwebsite.
Thebenefitsof usinghydrogen carrier gas for thePONAanalysis areobvious:
all critical components are resolved, per method D-6703-01, in the greatly
reduced time of 70.5minutes (C13), versus 146minutes or 97minutes using
helium.Relative to the results anticipated in themethod,wevirtuallydoubled
sample throughput.
Weevaluateeachcolumn for film thickness,columnefficiency,peak skewness,
selectivity, resolution, andbleed toguaranteeperformance and reproducibili-
ty from column to column. The redesigned Rtx®-1PONA column earned
Restek chemists the Concluded Research Award at the 2004 Gulf Coast
Conference.WhenyouuseanRtx®-1PONAcolumn,we thinkyou’ll agree the
awardwaswell justified.
Rtx®-1PONAColumn (fusedsilica)
(Crossbond
®
100% dimethyl polysiloxane)*
*Optimized phase for hydrocarbon analysis
ID
df (µm) temp. limits
length cat.#
0.25mm 0.50 -60 to 300/340°C 100-Meter 10195
Rtx®-5PONATuningColumn (fusedsilica)
(Crossbond
®
5% diphenyl/95% dimethyl polysiloxane)
ID
df (µm) temp. limits
length cat.#
0.25mm 1.0
-60 to 325°C
5-Meter 10196
UniversalAngledPress-Tight®Connectors
• Ideal for connecting a tuning column to an
analytical column.
• Inert fused silica.
• Angle reduces strainon the connection.
• Fit all columnODs from0.33–0.74mm
(Restek0.1mm–0.53mm ID).
5-pk./price
25-pk./price
100-pk./price
20446
20447
20448
20482
20483
20484
Reference
1. Stidsen, G. and B. Burger,
Enhanced Rtx
®
-1PONA Column Improves
DetailedHydrocarbon Analysis,
Restek Advantage 2005v1: 12 (2005).
please
note
To achieve critical resolutions in detailed hydrocarbon analysis, a
5-meter 5% diphenyl/ 95% dimethyl polysiloxane tuning column
(Rtx
®
-5PONA) is connected to the analytical column and adjusted
to the needed length through a series of trial analyses.
formore
info
!
Processed data for thePONAVI reference standard, containing
more than 400 individual components of finished gasoline, can be
reviewed on theRestekwebsite:
