ADV01-05_1-298

Figure 1

The Rtx

-OPPesticides 2 column shows excellent resolution of 53 organophosphorus pesticides.

• 14 •

www.restekcorp.com

by Gary Stidsen, Innovations Manager

Analyzing Organophosphorus

Pesticides

Using an Rtx

-OPPesticides2 Column

and GC/MS

✔

Low column bleed improves resolution of OPPs.

✔

Fast analysis times.

✔

Allows GC/MS analysis of many OPPs.

Typically, organophosphorus pesticides (OPPs) are

analyzed using a dual-column gas chromatograph

with flame photometric detectors (FPD) or nitrogen

phosphorus detectors (NPD). These detectors pro-

vide the sensitivity needed for reporting limits, but

only for a finite number of compounds. However,

the list of compounds continues to increase, due to

the introduction of new pesticides.

As the list of compounds grows, the use of gas

chromatography/mass spectrometry (GC/MS)

becomes more desirable. GC/MS analysis requires

only one column and detector, thereby eliminating

the complexity of the dual-column GC system.

Column bleed and analyte resolution are important

factors in GC/MS analysis. Minimizing column bleed

is important to increase the signal-to-noise ratio for

GC_EV00602

1. dichlorvos

2. hexamethylphosphoramide

3. mevinphos

4. trichlorfon

5. TEPP

6. demeton-O

7. thionazin

8. tributyl phosphate (IS)

9. ethoprop

10. naled

11. sulfotepp

12. phorate

13. dicrotophos

14. demeton-S

15. monocrotophos

16. terbufos

17. dimethoate

18. dioxathion

19. fonophos

20. diazinon

21. disulfoton

22. phosphamidon isomer

23. dichlorofenthion

24. chlorpyrifos methyl

25. phosphamidon

26. parathion-methyl

27. ronnel

28. fenitrothion

29. aspon

30. malathion

31. chlorpyrifos

32. trichloronate

33. parathion-ethyl

34. fenthion

35. merphos

36. chlorfenvinphos

37. crotoxyphos

38. stirofos

39. tokuthion

40. merphos oxon

(breakdown product)

41. ethion

42. fensulfothion

43 bolstar

44. carbophenothion

45. famphur

46. triphenyl phosphate (SS)

47. EPN

48. phosmet

49. leptophos

50. tri-

-cresyl phosphate

51. azinphos-methyl

52. azinphos-ethyl

53. coumaphos

Column:

Rtx

-OPPesticides2 30m, 0.25mm ID, 0.25µm (cat.# 11243)

Sample:

Custom Mix, plus:

8140/8141 OP Pesticides Calibration Mix A (cat.# 32277)

8141 OP Pesticides Calibration Mix B (cat.# 32278)

Triphenylphosphate Standard (cat.# 32281)

Tributylphosphate Standard (cat.# 32280)

1µL, 100ppm each (100ng on column)

Inj.:

1.0µL splitless (hold 0.4 min.), 4mm double

gooseneck inlet liner (cat.# 20785)

Inj. temp.:

250°C

Carrier gas:

helium, constant flow

Flow rate:

1.0mL/min.

Oven temp.:

80°C (hold 0.5 min.) to 140°C @ 20°C/min.

to 210°C @ 4°C/min. (hold 1 min.) to

280°C @ 30°C (hold 5 min).

Det:

Transfer line temp.:

280°C

Scan range:

35-400amu

Ionization:

the late-eluting compounds at the detection limits.

Although the MS can spectrally resolve the sample

components, fewer coelutions in the chromatogram

make data processing easier, including confirma-

tion by spectral identification.

Using sophisticated computer-assisted stationary

phase development (CASPD) software, Restek

chemists designed the Rtx

-OPPesticides2 column

to provide low bleed and improve resolution for

OPP analysis by MS (Figure 1). Not only are the

separations dramatically improved compared to tra-

ditional columns for this analysis, but also the

analysis time can be reduced by almost 50%.

The combination of an Rtx

-OPPesticides2 GC col-

umn with MS is an excellent system for analyzing

long lists of OPPs. The column exhibits very low

bleed and excellent resolution for these com-

pounds.