144 / 413
Increase Sample
Throughput for
Complex Drinking
Water Pesticides
Continued from page 1.
EPA Method 508.1 includes many of the components
as Method 505, a simi lar
GC/ECD
method, but also
contains several others, expanding the list to 38 com
pounds. Thi s method calls for solid phase extraction
and extract concentra tion , followed by an alysis using
a
GC/ECD
system. In order to increase sample
th roughp ut , an op timized method was developed
using a dual column configuration wit h th e Rtx®Cl.Pesticides/Rtxw-C l.Pesticides z column pair. These
columns, used und er the conditions shown, offer a
unique selectivity th at allows the target analytes to be
resolved in ap p roximately half the analysis time of th e
origina l me tho d (Figure
1).
There was one coelution
on th e primary column, but these compounds were
sepa rated on th e second column. Both columns easi
ly passed the comprehensive system performan ce cri
teria adapted from 508. 1 (Table 1).'
In conclusion, due to th e complexity of th e com
pound list in Meth od 508.1, a very high degree of
selectivity is required of the capillary column in order
to achieve ade qu ate reso lution of all target analytes in
a reasonable time. The op timized d ual colum n
method shown here offers a significantly faster analy
sis tim e, while ma inta ining excellent reso lution of
challenging drinking water pesticide s and herbicides.
References
1. http:/ /www.usda.gov/ nass/ pubs/trackrec/ trackOOa.htm#principaI
2. USEPA Method 508.1, JamesWEichelberger Rev 1.01994.
Conditions for Figure 1
Column:
Sample:
Inj.:
Inj. temp.:
Carrier gas:
Linear velocity:
Oventemp.:
Detector temp.:
Rtx®-CLPesticides2,
30~0.32mm!D,
0.251lm
(cat.# 11324)and
Rtx -CLPesticides,
30m, 0.32mm!D,0.3&,m (cat.# 11141) with
5m
x
0.32mm!D Rxi deactivated guard tubing
(cat.# 1003cW, connectedusing Universal
"Y"
Press-Tight
R
Connector (cat.# 20405-261)
50ng/mL 508.1 CalibrationMix# 1 (cat.# 32094),
100ng/mL 508.1CalibrationMix#2 (cat.# 32095),
100ng/ mL508.1 CalibrationMix #3 (cat.# 32096),
50ng/mL508.1 Internal Standard (cat.# 32091),
250ng/ mL508.1 Surrogate (cat.# 32092),
500ng/ mLAtrazine(cat.# 32208),
500ng/ mLSimazine (cat.# 32236) in ethyl acetate
2IlLsplitless (hold 0.75 min.), 4mmcycledouble
gooseneck liner (cat.# 20896)
250°C
helium, constant flow
26cm/ sec. @ 80'C
80'C (hold 0.5 min.)to 155'C(hold 1 min.) @
19' C/min. to 210' C@ 4'C/min. to 3WOC
(hold 0.5 min.) @ 25°C/ min.
ECD @ 32S
c
C
Figure 1
Resolve all critical pairs using Rtx®-CLPesticides and
Rtx®-CLPesticides2 columns.
27.4,4'-DDE
1. hexachlorocyclopentadiene
14. heptachlor
28. dieldrin
2. etridiazole
15. chlorothalonil
29. endrin
3. chlorneb
16. metribuzin
-
6
23 25
2 28
29 3132
7
26
11
1
J
J
~ lt
1
0
"!i ii i i i i ii i ii i
i i i i i i i ii
ii i
I '
I
2d.o
I
~o
13.0
~o
0
I
,-1,
1
2
21
I
1
16
14
17,18
I
i
6
19
i
12
I
i
i
2~
I
4. propachlor
17. alachlor
5. trifluralin
18. aldrin
6.
hexachlorobenzene
19. 4,4'-dibromobiphenyl (55)
7. a -BHC
20. metachlor
8. simazine
21. DCPA
9. atrazine
22. heptachlor epoxide
10. pentachloronitrobenzene (IS)
23. y-chlordane
11.y-BHC
24. cyanazine
12. P-BHC
25. a -chlordane
13.
i)-BHC
26. endosulfanI
Rtx"'-CLPesticides2
I
I
I
I
I
i
I
I
I
I
I
I
I
10
GCEVOl023
30. cnlorobenzilate
31.4,4'-DDD
32. endosulfanII
33. 4,4'-DDT
34. endrin aldehyde
35. endosulfansulfate
36. methoxychlor
37. cis-permethrin
38. trans-permethrin
33
34
22.0
37
,~
,
I
,
, ,
I
i
min.
Ido
Rtx"'-CLPesticides
28
29 31 32
27
1
7
11
2
6
10
Vi
,J
30
~
8
~
'--~
~
~
II I I i i i
I
I i
I
I I I I I i I
I '
I i I
I ' ,,,,,,,
id
.~
,,,,,,,
iL~
,,
'I
20.0
21.0
23
25
I
3 3
2
13
16,14
15
21
I
34
18
I
20,22
3
19
I
3
1
3
lY
37
I
I
I
10
'~
'LLJ
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