19
In addition to using a clean and deactivated injection port liner, we recommend using a five-
meter deactivated guard columnwhen analyzing dirty samples. Routinemaintenance of the
liner and the guard columnwill prevent dirty samples from contaminating the analytical col-
umn, andwill help ensure reproducible and accurate analytical results.
Hints for Performing Routine Injection PortMaintenance
Injection port maintenance should be performed prior to installing any capillary column.
Maintenance of the injection port after a column is installed should be performed periodical-
ly, based on the number of injectionsmade and the cleanliness of the samples.Maintenance
includes cleaning, deactivating, or replacing injection port liners, and replacing critical inlet
seals and the septum. Review the instrument manual inlet diagram prior to disassembling
the inlet.
Cleaning andDeactivating Injector Liners
For optimum column performance, the injection port linermust be free of septum particles,
sample residue, and ferrule fragments. Use a deactivated injection port liner when analyzing
sampleswith compounds that are active or prone to decomposition or adsorption on untreat-
ed glass surfaces. TableV illustrates the importance of a deactivated injection port liner
when analyzing active compounds. The response factors (RF) for all three of these active
compoundsweremuch lower with non-deactivated inlet liners.
If the injection port liner is deactivated and is not excessively dirty, cleaningwith organic
solvents usually is enough to restore original performance.Most organic solventswill not
affect the integrity of the surface deactivation. First, remove septum particles that adhere to
the insidewall of the injection port liner by rinsingwithmethanol or isopropanol. Next, use
pentane, methylene chloride or toluene to remove sample residue. Do not use laboratory
detergents, acids, or bases to clean injection port liners. Harsh cleaning agentswill remove
or damage the deactivation layer and the liner will require re-deactivation. Nylon brushes
and pipe cleaners (cat.# 20108) can be used formild abrasive cleaning of injection port liners.
ReplacingCritical Seals
Replace critical seals prior to installing an injection port liner (see the instrument manual for
seal locations). Inmost capillary injection ports, an o-ring or ferrulemade of rubber or
graphite is used to seal the injection port liner into the injection port body. It is critical that
the seal fits tightly around the liner, to prevent the carrier gas from leaking around the out-
side of the liner. Check for leakswith a thermal conductivity-type leak detector (e.g., Leak
Detective
™
II, cat.# 20413).
Changing Septa
Always use a high-quality, low-bleed septum.We recommend replacing the septum fre-
quently, to prevent leaks and fragmentation.Multiple injections and continuous exposure to
hot injection port surfaceswill decompose the septum and cause particles to fall into the
injection port liner. Septum particles are a potential source of ghost peaks, loss of inertness,
and carrier gas flow occlusion. It is best to install a new septum at the end of an analytical
sequence so that it can condition in the injector and reduce the incidence of ghost peaks. To
avoid contamination, always use forcepswhen handling septa. Restek’s high quality, low-
bleedThermolite
®
septa are available formost commonmodels of capillaryGCs. Formore
information, request a copy of Restek’s
Guide toMinimizing SeptaProblems
(lit. cat.#
59886).
Compound
RFDeactivatedLiner RFUndeactivatedLiner
2,4-dinitrophenol
0.248
0.185
pentachlorophenol
0.240
0.188
benzidine
0.327
0.234
Table V.
Deactivated inlet liners show higher response factors for active components.
RF
relative to
naphthalene;
N=3
For additional hints for analyzing dirty samples, request a copy of Restek’s
AGuideWhen
InjectingDirty Samples
(lit. cat.# 59881).
Nylon TubeBrushes andPipe
Cleaner
Use to remove small septum fragments
and residue from dirty glass inlet liners.
Brushes are
1
/
8
-,
3
/
16
-, and
1
/
4
-inch indiam-
eter; pipe cleaner is one foot long.
LeakDetective
™
II
LeakDetector
• Affordable thermal conductivity leak
detector—every analyst canhaveone.*
• Compact, ergonomicdesign is easy to
hold and operatewith one hand.
• Helium, hydrogen, and nitrogen can
be detected at 1x10
-4
cc/sec. or at an
absolute concentration as low as
100ppm.**
• Fast results—responds in less than 2
seconds to trace leaks of gases with
thermal conductivitiesdifferent thanair.
• Micro-chip design improves sensitivity
and response timeoverpreviousmodels.
• Autozeroingwith the touchofabutton.
• Battery-operated for increased porta-
bility (one 9-volt).
Description
qty. cat.#
Leak Detective
™
II
Leak Detector
(9 volt, Battery-Operated)
ea. 20413
Description
qty. cat.#
Nylon Tube Brushes and Pipe
Cleaner
set 20108
*Never use liquid leakdetectors ona capillary sys-
tembecause liquids canbedrawn into the column.
**Caution: NOTdesigned for determining leaks of
combustiblegases.A combustiblegas detector
shouldbeused for determining combustiblegas
leaks inpossiblyhazardous conditions.
