SeptumHandling
All septa, regardless of their composition, puncturability, or resistance to thermal
degradation,will be a source of problems if they aremishandled.Always use clean
forceps orwear clean cotton gloveswhenhandling septa; donot handle themwith
bare fingers, norwithpowdered latex gloves—contaminants such as finger oils, per-
fumes,make-up, fingernail polish, skin creams, hand soaps, and talcum canbe
absorbed into the septum andwill bleed from the septumduring your analyses.
Also, follow septum and instrumentmanufacturers’ recommendationswhen installing a septum.Overtightening a septumnut invari-
ablywill reduce septum lifetime by increasing septum coring and splittingproblems.
SeptumBleed
All septa contain various amounts of volatilematerials (e.g., silicone oils, phthalates) that canbe releasedwhen the septum is heated
to analysis temperatures. Septumbleedoccurswhen these volatiles from the septum collect on the column, then elute from the col-
umn and create baseline disturbances or extraneous (ghost) peaks in the chromatogram.This problem is prevalent in temperature-
programmed analyses, because the septum volatiles collect on the columnduring the oven cool-down and initial holdperiods.
Capillary columns requiremuch lower gas flow rates thanpacked columns, therefore septum volatiles aremore concentrated, and
bleedproblems aremore pronounced in capillaryGC systems.
BecausemostGCs are equippedwith a septumpurge, septumbleed generallywill disap-
pearwithin30minutes after installing anew septum and exposing it tonormal injector
temperatures.All Restek septa eliminate this conditioningperiodbecause they are pre-
conditioned and canbeusedwithout delay.
WhyareLow-BleedSepta Important?
Either baseline rise or extraneous peaks causedby septumbleed can interferewith identi-
fication andquantificationof target analytes.And, because septumbleed is inconsistent,
method reproducibility canbe aproblem.Using low-
bleed septa canminimize these effects andhelp
producemore reliable results.
WhyDoesSeptumPuncturabilityMatter?
A septum that canbe penetrated cleanly and easilyby a syringeneedle has a
longer life, and consistent injectionsmade through such a septumhelp
ensure accurate results.The soft silicone rubber fromwhich all Restek
septa aremanufactured is specially formulated for chromatographic
performance,which ensures our septa are easy topuncture.
AVOID
SEPTUM
PROBLEMS
SEPTUM
HANDLING
TIPS
• Handle septa carefully, toprevent
contamination.
• Minimizebleed—useprecondi-
tioned, low-bleed septa.
• Follow septumand instrument
manufacturers’ recommendations.
