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Figure 1 Resolve all critical pairs using Rtx®-CLPesticides and
Rtx®-CLPesticides2 columns.
• 4 • 2008 vol. 2
Environmental
Increase Sample
Throughput for
Complex Drinking
Water Pesticides
Continued from page 3.
EPA Method 508.1 includes many of the compo-
nents as Method 505, a similar GC/ECD method,
but also contains several others, expanding the list
to 38 compounds. This method calls for solid
phase extraction and extract concentration, fol-
lowed by analysis using a GC/ECD system. In
order to increase sample throughput, an opti-
mized method was developed using a dual column
configuration with the Rtx®-CLPesticides/Rtx®-
CLPesticides2 column pair. These columns, used
under the conditions shown, offer a unique selec-
tivity that allows the target analytes to be resolved
in approximately half the analysis time of the orig-
inal method (Figure 1). There was one coelution
on the primary column, but these compounds
were separated on the second column. Both
columns easily passed the comprehensive system
performance criteria adapted from 508.1 (Table I).2
In conclusion, due to the complexity of the com-
pound list in Method 508.1, a very high degree of
selectivity is required of the capillary column in
order to achieve adequate resolution of all target
analytes in a reasonable time. The optimized dual
column method shown here offers a significantly
faster analysis time, while maintaining excellent
resolution of challenging drinking water pesticides
and herbicides.
References
1.
2. US EPA Method 508.1, James W Eichelberger Rev 1.0 1994.
GC_EV01023
GC_EV01022
1. hexachlorocyclopentadiene
2. etridiazole
3. chlorneb
4. propachlor
5. trifluralin
6. hexachlorobenzene
7. α-BHC
8. simazine
9. atrazine
10. pentachloronitrobenzene (IS)
11. γ-BHC
12. β-BHC
13. δ-BHC
Conditions for Figure 1
Column: Rtx® -CLPesticides2,
30m, 0.32mm ID, 0.25µm (cat.# 11324) and
Rtx® -CLPesticides,
30m, 0.32mm ID, 0.32µm (cat.# 11141) with
5m x 0.32mm ID Rxi® deactivated guard tubing
(cat.# 10039), connected using Universal “Y”
Press-Tight® Connector (cat.# 20405-261)
Sample: 50ng/mL 508.1 Calibration Mix #1 (cat.# 32094),
100ng/mL 508.1 Calibration Mix #2 (cat.# 32095),
100ng/mL 508.1 Calibration Mix #3 (cat.# 32096),
50ng/mL 508.1 Internal Standard (cat.# 32091),
250ng/mL 508.1 Surrogate (cat.# 32092),
500ng/mL Atrazine (cat.# 32208),
500ng/mL Simazine (cat.# 32236) in ethyl acetate
Inj.: 2µL splitless (hold 0.75 min.), 4mm cyclo double
gooseneck liner (cat.# 20896)
Inj. temp.: 250°C
Carrier gas: helium, constant flow
Linear velocity: 26cm/sec. @ 80°C
Oven temp.: 80°C (hold 0.5 min.) to 155°C (hold 1 min.) @
19°C/min. to 210°C @ 4°C/min. to 310°C
(hold 0.5 min.) @ 25°C/min.
Detector temp.: ECD @ 325°C
Rtx®-CLPesticides
Rtx®-CLPesticides2
14. heptachlor
15. chlorothalonil
16. metribuzin
17. alachlor
18. aldrin
19. 4,4'-dibromobiphenyl (SS)
20. metachlor
21. DCPA
22. heptachlor epoxide
23. γ-chlordane
24. cyanazine
25. α-chlordane
26. endosulfan I
27. 4,4'-DDE
28. dieldrin
29. endrin
30. chlorobenzilate
31. 4,4'-DDD
32. endosulfan II
33. 4,4'-DDT
34. endrin aldehyde
35. endosulfan sulfate
36. methoxychlor
37. cis-permethrin
38. trans-permethrin