154 / 298
Figure 2
Stx
™
-CLPesticides and Stx
™
-CLPesticides2 columns provide rapid, excellent separation of chlorinated pesticides, and a Siltek
™
-deactivated Drilled
Uniliner
®
inlet liner helps ensure high responses for sensitive analytes.
• 12 •
www.restekcorp.comby Gary Stidsen, Innovations Manager
Inert Inlet System Improves
Responses for Chlorinated
Pesticides
Using the Drilled Uniliner
®
Inlet Liner
✔
Inert sample path eliminates injection port discrimination.
✔
Reduce detection limits by using a splitless injection port without an on-column
injector.
For years, chemists analyzing chlorinated pesticides
have tried many different injection techniques in
attempts to find the best balance between inertness
and ability to contend with sample contamination.
Cool on-column, split, splitless, and direct injec-
tion, and variations of these injection techniques,
are used today.
Now, a specially modified injection port liner, devel-
oped by Restek chemists, reduces sample contact
with active metal parts in split/splitless injection ports.
This Drilled Uniliner
®
liner, shown in Figure 1, gives
the benefits of both direct injection and splitless
injection. The advantage of this liner is that the col-
umn is connected to the liner by a press-fit connec-
tion, thus preventing the sample from contacting the
metal at the bottom of the injection port. Also, the
hole on the side of the liner allows the purge flow to
escape from the liner when the injection mode is
switched from splitless to split.
Inertness
With the Drilled Uniliner
®
liner, the sample is trans-
ferred directly from the injection port to the col-
umn and contacts only this glass inlet liner. The
configuration allows the sample to be "funneled"
into the column entrance, thereby eliminating the
need for vaporization aids such as fused silica
wool. The test probes endrin and 4,4'-DDT are
good indicators of injection port inertness. Analyses
of the performance evaluation mixture (PEM) show
low breakdown of these compounds when using
this liner.
For maximum inertness, we recommend using the
Drilled Uniliner
®
liner in combination with an Stx
™
-
CLPesticides capillary column, as shown in Figure
2. Siltek
™
surface deactivation in these columns fur-
ther ensures maximum responses for the labile pes-
ticides endrin, 4,4'-DDT, and methoxychlor. A spe-
cial polymer formulation designed for organochlo-
rine pesticides enables you to achieve excellent sep-
aration of the 22 chlorinated pesticides in Figure 2
in less than 15 minutes. Comparable analyses on
Rtx
®
-CLPesticides columns take up to 24 minutes
(Figure 2, inset).
Calibration
Linearity and continuing calibration checks for the
chlorinated pesticides also are critical parameters
that must be monitored. Table 1 indicates typical
1. 2,4,5,6 tetrachloro-
m
-xylene (IS)
2.
α
-BHC
3.
γ
-BHC
4.
β
-BHC
5.
δ
-BHC
6. heptachlor
7. aldrin
8. heptachlor epoxide
9.
γ
-chlordane
10.
α
-chlordane
11. 4,4'-DDE
12. endosulfan I
13. dieldrin
14. endrin
15. 4,4'-DDD
16. endosulfan II
17. 4,4'-DDT
18. endrin aldehyde
19. methoxychlor
20. endosulfan sulfate
21. endrin ketone
22. decachlorobiphenyl (IS)
Oven temp.:
110°C (hold 1 min.) to 245°C @ 20°C/min.
to 300°C @ 6°C/min.
Inj. & det. temp.:
210°C / 310°C
Carrier gas:
helium
Dead time:
0.8min. @ 120°C
Inlet liner:
Siltek
™
Drilled Uniliner
®
liner (cat.# 21055-214.5)
Inj.:
1µL direct injection of 20/40/200ng/mL std.
concentration in hexane
Make-up gas:
nitrogen
1
2 3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
30m, 0.32mm ID, 0.5µm
Stx
™
-CLPesticides
(cat.# 11544)
30m, 0.32mm ID, 0.25µm
Stx
™
-CLPesticides2
(cat.# 11444)
1
2
3
4
5
6
7
8
9
10
12
11
13
14
15
16
1718
19
20
21
22
GC_EV00512
Figure 1
The drilled hole in a Uniliner
®
injection port
liner makes direct injection possible with
EPC systems by equalizing pressure in the
injection port.
8
10
12
14 min.
8
10
12
14 min.
6
9
10
11
12
13
14
15
16
17
18
19
20
1
2
3
4
5
6
7
8
21
22
min. 10
24
GC_EV00075
On-column concentration:
16–160pg organochloride
pesticide mix AB#2
(cat.# 32292)
Oven temp.:
120°C (hold 1 min.) to 300°C
(hold 10 min.) @ 9°C/min.
Inj. port:
Direct, Uniliner
®
liner
(cat.# 20335), at 200°C
Detector:
ECD, 300°C with Anode Purge
Dead time:
1.9 min.
Head pressure:
8.7psi (constant)
Flow rate:
1.3mL/min. @ 120°C, helium.
30m, 0.32mm ID, 0.25µm
Rtx
®
-CLPesticides2
(cat.# 11324)
Traditional analyses on
Rtx
®
-CLPesticides columns take
up to 24 minutes.