11
Inlet Liners for Splitless Injections
The residence time of the sample in a splitless liner is between 0.5 and 2minutes, so splitless
inlet liners do not require large surface areas for efficient vaporization (unless you are using
a rapid-injecting autosampler). Splitless liners usually are designed as straight tubes.Alterna-
tive splitless liner designs, such as gooseneck restrictions, help contain the sample cloud in
the injector andminimize the breakdown of compounds sensitive to catalytic decomposition
onmetal inlet parts. Splitless liners should be packedwithwool or fused silica beads to help
with vaporization, trap non-volatile residue, and prevent column contaminationwhen analyz-
ing dirty samples. Some of themore commonly used splitless liners are described below.
A) Straight Tube
Use for samples containing a narrow molecular
weight distribution and for those not prone to
thermal decomposition. Packingwithwool is rec-
ommended. Wool aids in vaporization of high
molecular weight compounds andminimizes dis-
crimination.
Benefits:
•
Low cost.
Drawbacks:
•
Potential decomposition of active compounds
such as endrin and phenolswhen packedwith
wool.
•
Prone to highmolecular weight
discrimination.
•
Sample exposed tometal surface below liner.
B) Gooseneck
C) RecessedGooseneck
Benefits:
•
Increases splitless efficiency.
•
Decreases breakdown of active compounds
such as endrin andDDT.
•
Chamber contains sample vaporization cloud.
•
Can be packedwithwool.
Drawbacks:
•
No known drawbacks.
D) DoubleGooseneck
E) RecessedDoubleGoosen
eck
Best liner for catalytically labile or highmolecu-
lar weight compounds. Isolates sample from
metal injection port parts. Use the cyclo-version
for dirty samples.
Benefits:
•
Highest splitless efficiency.
•
Breakdown of active compounds decreased.
•
Chamber contains vaporization cloud.
Drawbacks:
•
Higher cost than straight splitless liners.
•
Only recesseddoublegoosenecks canbepacked
withwool.
Note:
Recessed gooseneck liners offer the same
benefits as single or double gooseneck liners, but
the base of the recessed gooseneck can be packed
with wool and the liner can be used for dual-col-
umn analysiswith a two-hole ferrule.
F) DrilledUniliner
®
This direct injection liner features a hole drilled
into the inlet end that reduces sample discrimina-
tion, compared to typical splitless injections.
Benefits:
•
Excellent transfer of analytes to column.
•
Decreases injection port discrimination.
•
Removes excess solvent vapor.
•
Eliminates the need for wool.
•
No sample contact withmetal parts below liner,
less adsorption.
Drawbacks:
•
Higher amounts of non-volatile materials
transferred to column.
G) 4mmSplitless withFused SilicaWool
The wool provides a large surface area to allow
rapid vaporization of the sample and deliver a uni-
form vapor cloud to the split point. The lowmass
of thewool fiber promotes complete vaporization.
Benefits:
•
Low cost.
•
Reproducible performance.
Drawbacks:
•
Wool can be adsorptive, especially if fibers are
broken.
•
Highmaintenance requirements.
A
B
C
D
E
F
G
010 %
deactivated
all liners are
See page 17.
All Restek liners are deactivated to prevent
adsorption of active compounds. Call for
information on custom deactivations.
