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GC Accessories
Consider Resealability
Multiple injections can core the vial cap septum and lead to significant bleed.
Resistance to coring varies by septum material (Figure 5). Coring can be min-
imized by preparing separate vials for replicate injections, when feasible, and
by carefully considering the type of septum material when multiple injections
are necessary. Septum resealability also affects evaporative loss, which can be a
significant source of error for low volume samples. For example, a relatively
nonvolatile analyte in a volatile solvent can concentrate significantly due to
evaporative loss (Figure 6). Vials should be recapped when necessary for
extended runs or long term storage.
Conclusion
Septum bleed is not a very common occurrence, but when bleed does occur, it
is easy to assume the injection port septum is the source because the vial cap
septum often is not considered. However, correctly diagnosing the source of
bleed contamination can save time and effort by preventing unnecessary injec-
tion port maintenance. Effectively and efficiently reducing interfering peaks by
controlling septum bleed can significantly improve analytical performance,
particularly for trace analyses.
Figure 3
PTFE lining prevents bleed due to
solvent/septum interaction.
Figure 4
Unlined septa show bleed
contamination within 24 hours.
Figure 5
Bleed contamination increases
over multiple injections.
Figure 6
This bar graph shows the volume
of solvent lost for three septum types.
Crimp-Top Vials, Snap Seal™ Style—12 x 32mm, 11mm Crimp
Description
100-pk.
1000-pk.
2.0mL Clear Glass Vial w/White Graduated Marking Spot
24383
24384
2.0mL Amber Glass Vial w/White Graduated Marking Spot
24385
24386
2.0mL Clear Glass Vial without Graduated Marking Spot
21152
21153
2.0mL, 11mm Aluminum Crimp Seals with Septa
Description
100-pk.
1000-pk.
Silver Seal, PTFE/Natural Rubber Septa
21174
21175
Red Seal, PTFE/Red Rubber Septa
24355
24356
Silver Seal, PTFE/Silicone Septa
24359
24360
Limited Volume Inserts for 2.0mL Crimp-Top & Short-Cap,
Screw-Thread Vials
Description
100-pk.
1000-pk.
350µL Glass, Flat Bottom Insert w/ ID Ring
24692
24693
Rtx®-5MS—Low-bleed GC/MS Columns (fused silica)
(Crossbond
®
5% diphenyl/95% dimethyl polysiloxane)
ID
df (µm)
temp. limits
length
cat. #
price
0.25mm
0.25
-60 to 330/350°C
30-Meter
12623
Split Liners for Agilent GCs
ID* x OD & Length (mm)
qty.
cat.#
price
4mm Split w/ Wool
4.0 ID x 6.3 OD x 78.5
ea.
20781
4.0 ID x 6.3 OD x 78.5
5-pk.
20782
4.0 ID x 6.3 OD x 78.5
25-pk.
20783
*Nominal ID at syringe needle expulsion point.
Vials were prepared with methylene chloride and stored at room temperature.
Vials were prepared with methylene chloride, sealed with caps contain-
ing septa that were inserted upside down in order to expose the non-PTFE
lined septum surface to the solvent, and stored at room temperature.
Vials containing 300µL of methylene chloride were punctured and left
at room temperature for 24 hours.