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Articles on pages 4 and 7 of this Advantage
describe analyses of phenols and active semivolatile
organic compounds that are notoriously difficult to
analyze, particularly at low concentrations. Low-
level injections reduce sensitivity for these com-
pounds, due to degradation or irreversible adsorp-
tion in the injection port. Residues of heavier and
non-volatile materials often build up at the bottom
of the injection port, leaving a reactive surface that
can cause active compounds to break down.
To circumvent this problem, we use a deactivated,
Drilled Uniliner ® inlet liner (Figure 1) in the inlet,
in place of a standard splitless inlet liner, to mini-
mize sample exposure to the hot metal surfaces of
the injection port. A Drilled Uniliner ® liner makes a
press-fit connection between column and liner,
eliminating the primary source of analyte break-
down. This physical connection between column
and liner also improves sensitivity, by minimizing
injection port discrimination. Further, with a Drilled
Uniliner ® inlet liner less of the injected sample is
vented, should you need to switch from splitless to
split mode to sweep remaining solvent from the
inlet. This too contributes to greater sensitivity.
We tested the performance of a system that included
a Drilled Uniliner® inlet liner, using a mixture of
chlorinated pesticides at 20, 40, and 200ng/mL con-
centrations (Restek Advantage 2002v4). The per-
cent difference between the observed value and the
"true" value for each analyte ranged from 0% to a
maximum of only 6.4%. The system that included the
Drilled Uniliner® inlet liner reduced endrin and DDT
breakdown, relative to systems that included splitless
liners (Table 1), because a splitless liner allows the
analytes to contact active surfaces in the inlet. Wool
packing in the splitless liner aggravates this problem,
by greatly increasing the surface area within the liner
and introducing additional active sites.
In addition to reducing variability and increasing
accuracy of calibration data, a Drilled Uniliner®
inlet liner increased overall response for individual
analytes, enhancing minimum detection levels com-
pared to standard splitless inlet liners. In the pesti-
cides test, area counts for the last eluting peak,
decachlorobiphenyl, were greater by 18-39% when
a Drilled Uniliner® inlet liner was used, relative to
area counts for injections made on splitless liners
(Table 1).
By eliminating the bottom of the injector from the
sample pathway, a Drilled Uniliner® inlet liner
makes the pathway more inert. This can increase
accuracy and precision, and reduce breakdown of
active analytes, relative to hot flash injection tech-
niques. If you are conducting analyses of phenols,
chlorinated pesticides, or other active analytes,
these results clearly show that a Drilled Uniliner®
inlet liner could be the liner of choice.
by Gary Stidsen and Lydia Nolan, Innovations Team
Improved Responses for Active
Analytes
Using a Drilled Uniliner® GC Inlet Liner
✔ Less breakdown of active compounds, for more accurate results.
✔ Greater sensitivity, for lower detection limits.
✔ Minimal injection port discrimination.
DI Liners for Agilent 5890 & 6890 GCs
(For 0.25/0.32/0.53mm ID Columns)
ID*/OD &
Length (mm)
cat.#/price
ea.
cat.#/price
5-pk.
Drilled Uniliner®
4.0 ID
6.3 OD x 78.5
21054 21055
Siltek™ Drilled Uniliner ®
4.0 ID
6.3 OD x 78.5
21054-214.1 21055-214.5
Siltek™ 1mm Drilled Uniliner®
1.0 ID
6.3 OD x 78.5
21390-214.1 21391-214.5
Hole makes
direct injection
possible with
EPC-equipped
Agilent 6890
GCs!
% Breakdown Drilled 4mm splitless 4mm splitless
Analyte Column Uniliner® with wool
Endrin Rtx®-CLPesticides 4.4 4.7 9.8
Rtx®-CLPesticides2 4.9 6.9 8.3
DDT Rtx®-CLPesticides 0.2 0.3 2.6
Rtx®-CLPesticides2 0.3 0.9 3.1
Response—Mean response; value in table x 103 = response units.
Drilled 4mm splitless 4mm splitless
Analyte Column Uniliner® with wool
Tetrachloro- m- Rtx®-CLPesticides 147 111 106
xylene (TCMX) Rtx®-CLPesticides2 191 167 162
Decachloro- Rtx®-CLPesticides 150 119 108
biphenyl (DCB) Rtx®-CLPesticides2 209 177 166
Table I
Lowest breakdown of endrin and DDT, and highest responses for analytes, using a Drilled
Uniliner® inlet liner.
*Nominal ID at syringe needle expulsion point.
Figure 1
Reduce the loss of active analytes—use a Drilled Uniliner® inlet liner.
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