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GC_EV00394
Column: Rtx®-OPPesticides2, 30m, 0.32mm ID, 0.32µm (cat.# 11241)
Inj.: 1µLsplitless injection of 100ng/mLcustomOPpesticidesmix described inFigure 3 (GC_EV00602)
Oven temp.: 80°C (hold 0.5min.) to 280°C@ 12°C/min. (hold 10min.)
Injector: 200°C
Inlet liner: 4mmSiltek™ single gooseneck (cat.# 20798)
Detector: FPD@ 250°C;
Dead time: 1.03min.@ 80°C
Splitless hold: 1min.
1. dichlorvos
2. hexamethylphosphoramide
3. mevinphos
4. trichlorfon
5. TEPP
6. demeton-O
7. tributylphosphate (SS)
8. thionazin
9. ethoprop
10. naled
11. sulfotepp
12. phorate
13. dicrotophos
14. monocrotophos
15. demeton-S
16. terbufos
17. dimethoate
18. diazinon
19. dioxathion
20. fonophos
21. disulfoton
22. phosphamidon isomer
(breakdown product)
23. dichlorofenthion
24. phosphamidon
25. chlorpyrifosmethyl
26. parathion-methyl
27. ronnel
28. aspon
29. fenitrothion
30. malathion
31. chlorpyrifos
32. trichloronate
33. parathion-ethyl
34. fenthion
35. merphos
36. chlorfenvinphos
37. crotoxyphos
38. stirofos
39. tokuthion
40. merphos oxone
(merphos breakdown product)
41. ethion
42. fensulfothion
43. bolstar
44. carbophenothion
45. famphur
46. triphenylphosphate (SS)
47. EPN
48. phosmet
49. leptophos
50. tri-o-cresyl phosphate
51. azinphos-methyl
52. azinphos-ethyl
53. coumaphos
Restek’s proprietary computer-assisted stationary phase develop-
ment (CASPD)modeling softwarewas used to develop the new
phase. This software predictsGC polymer phase selectivity based
on the retention of key analytes under controlledGC conditions.
The stationary phase selectivity can be optimized, often resulting
in the design of a completely new phase. In this case the new
phase, Rtx ®-OPPesticides2, achievesmuch better resolution of the
OPPs than traditionally used columns, with only two coeluting
pairs. Thismakes the new column an ideal primary column, even
exceeding the performance of theRtx® -OPPesticides column, for
analyses of organophosphorus pesticides (Figure 2).
TheRtx®-OPPesticides2 column has quickly become aworkhorse
column for laboratories analyzing organophosphorus pesticides.
GC/MSAnalysis
In somemethods, such as in food analysis, low-level detection of
organophosphorus pesticides is not as important as the positive
identification of the pesticides. In these cases aGC/MS analysis is
the best approach. TheRtx®-OPPesticides2 column is an excellent
choice for GC/MS because the column exhibits low bleed and
maximizes resolution of the organophosphorus pesticides. Figure 3
shows a typical GC/MS analysis.
Effect of CarrierGas Flow
Flow conditions are extremely important to achieving the desired
resolutions of OPPs. The chromatograms in Figure 4 are results
from a flow rate study on theRtx® -OPPesticides2 column. Flow
can be used to enhance resolution and affect elution order. Because
of the close elutions of somany of these compounds, it is critical to
measure analytical velocity as either flow rate through the column
or as dead time of an unretained analyte. Note that retention times
and resolution (and, potentially, elution order) can shift with rela-
tively small changes in dead time. In this analysis, we recommend
using a slightly lower flow rate (longer dead time) to achieve the
best overall separation.
Conclusion
Organophosphorus pesticides analyses can present many challenges
to the analyst, but theRtx®-OPPesticides2 andRtx®-OPPesticides
column pair ensures quick analysis, exceptional resolution, and
confirmation formore than 48OPPanalytes and their degradation
products in a single, dual-column run.
1. USEPAMethod 8141AOrganophosphorus Compounds byGas
Chromatography: CapillaryColumnTechnique.
Figure 2—TheRtx®-OPPesticides2 column is an ideal primary column for fast, sensitive analyses of
organophosphorus pesticides.
Restek Corporation • (800) 356-1688 • (814) 353-1300 •www.restekcorp.com