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handy septum
size chart
Septum
Diameter
Instrument (mm)
Agilent (HPJ
5880A, 5890, 6890,
6850,PTV 11
5700,5880 9.5/10
On-Column Injection
CE Instruments (TMQJ
TRACE~ GC 17
Finnigan (TMQJ
GC 9001 9.5
GCQ 9.5
GCQ w/TRACF", PTV 17
QCQ~ 9.5
TRACF" 2000 9.5
Fisons/carloErba(IMQ)_
8000 series E_
Gow-Mac
6890 series 11
Al othermodels 9.5
PerkinElmer
Sigma series 11
900,990 11
8000 series 11
Auto SYS'" 11
Auto SYS~ XL 11
Pye/Unicam
All models
Shimadzu
Allmodels Plug
SRl
Allmodels Plu
Tracor
540 11.5
550,560 9.5
llQ,222 12.5
Varian
Injector type:
Packedcolumn 9.5/10
Splitlsplitless
1078/1079 1O1ll
1177 9
1075/1077 11
did you know?
Restek's newThermolite'"
andIceBlue'" septa are now
precision molded to ensure
consistent, accurate fit.
2006 vol. 1
Peak Performers
Avoid Septum Problems
ByDonna Lidgett, GC Accessories Product Marketing Manager
• Handle septa carefully, to prevent contamination.
• Use low-bleed septa.
Septum Handling
All septa, regardless of their composition, puncturability, or resistance to thermal degradation , will be a
source of problems if they are misha ndled. Always use clean forceps or wear clean cotto n gloves when
handl ing septa; do not handle them with bare fingers, nor with powdered latex gloves-contaminants
such as finger oils, perfumes, make-up , fingernai l polish, skin creams, hand soaps, and talcum can be
absorbed into th e septum and will bleed from the septum during your analyses.
Also, follow septum and instrument manu facturers' recommendations when installing a septum.
Overt ightening a septum nut invariably will redu ce septum lifetime by increasing septum coring and
splitting problems.
Septum Bleed
All septa contain vario us amo un ts of volatile materials (e.g., silicone oils, phthalates) that can be released
when the septum is heated to analysis temp eratures. Septum bleed occurs when these volatiles from the
septum collect on the column, then elute from the column and create baseline disturbances or extrane­
ous (ghost) peaks in the chromatogram. This problem is prevalent in temp erature-p rogrammed analy­
ses, because the septum volatiles collect on the column during th e oven cool-down and initial hold peri­
ods. Capillary colum ns require much lower gas flow rates than packed columns, therefore septum
volatiles are more concen tra ted, and bleed problems are more pronou nced in capillary GC systems.
Why are Low-Bleed Septa Important?
Either baseline rise or extra neous peaks caused by septum bleed can interfere with identification and
quantification of target analytes. And, because septum bleed is inconsistent, meth od reproducibility can
be a problem. Using low-bleed septa can minimize these effects and help produce more reliable results.
Why Does Septum Puncturability Matter?
A septum that can be penetrated cleanly and easily by a syringe needle has a longer life, and consistent
injections made through such a septum help ensure accurate results. The soft silicone rubb er from which
all Restek septa are manufactured is specially formulated for chromatograp hic perform ance, which
ensures our septa are easy to puncture.
What Septum Configurations are Available, and for Which GCs?
Restek has fashioned septa for all major brand s of gas chromatographs and injectors . Use th e septum size
chart to determine the septum diameter for your instrument or, contact us.
Which Septa Should I Use?
Therrnolitee septa are a proven low-bleed champion . With a maximum temperature of 340°C, there are
very few applications for which Thermolitev septa are not suitable.
Icelslue!" septa are ideal for analysts using inlet temp eratures of 250°C or below, or using solid phase
microextracti on (SPME) sampling techniques. Iceblue?' septa will accommodate punctur ing from the
large needles used in SPME, and still assure consistent injectio ns and lon g lifetime.
BTO®septa are bleed and temperature opt imized with a maximum tempera ture of 400°C, for the most
demanding GC and GC/MS app lication s. They retain remarkable softness and pierceability at high tem­
peratures. The Centerfl uide?" can help reduce coring when used with tapered (rounded-tip) needles.
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