• 7 •
800-356-1688
by Christopher English, Environmental Innovations Chemist
Analysis of European
OrganophosphorusPesticides
Fast, Complete ResolutionUsing an
Rtx
®
-CLPesticides Column
✔
Fastest analysis of 21 target OPPs and surrogates.
✔
Extremely low column bleed at temperatures >300ºC.
✔
Use Rtx
®
-CLPesticides columnswith FPDs, NPDs, or GC/MS systems.
Our European customers provided us with a list of
organophosphorus compounds and asked us to help
develop a GC analysis. Restek offers the analytical
reference standards, andwe now have determined
the chromatography column and conditions needed
for a problem-free analysis of thesematerials.
Organophosphorus pesticide (OPP) is a general term
that includes all phosphorus-containing insecticides.
Because these compounds eliminate target insects
effectively, thenbreakdown intonon-toxic derivatives,
they have replacedmany of the environmentally per-
sistent organochlorine pesticides. By 1959over
50,000different OPPs hadbeenprepared. OPPs are
hydrolyzedby bases and acids and are photosensitive,
whichmakes them ideal for agricultural applications.
Themain concernOPPs pose is the intact mole-
cules’ high toxicity tomammals—these chemicals
are considered themost toxic of all pesticides to
vertebrates. Further, at low levels, OPPs can be
endocrine-disrupting compounds (EDC) - materials
that interfere with hormone activities inmammals.
Dimethoate andmalathion have been shown to be
in this category. Consequently, dimethoate and
malathion are on the European Priority List; further
study is required to determine if use of these two
pesticides should be suspended.
We used computermodeling software to design the
Rtx
®
-CLPesticides column for analyses of chlorinat-
ed pesticides, but this column also is well suited for
analyses of electronegative species, such as OPPs.
We evaluatedmany columns for resolving this
selection of compounds, andwe found that the
Rtx
®
-CLPesticides column resolves these com-
pounds to baseline in the least amount of time.
The 30m x 0.25mm x 0.25µmRtx
®
-CLPesticides col-
umn configuration is best suited for GC/MS applica-
tions; a 30m x 0.32mm x 0.50µm column can be
usedwith direct injections and FPD or NPD detec-
tion. The GC/MS analysis is shown in Figure 1. For
the application shownwe added the surrogatesmost
commonly usedwith FPD or NPD detectors and
optimized conditions so that all compounds, includ-
ing the four added surrogates, are baseline resolved.
The high temperature stability of Rtx
®
-CLPesticides
columns enabled us to bring the oven temperature
to 330°C, following each analysis, to bake out high
molecular weight contaminants commonly found in
OPP-containing extracts. The ability to condition
these columns at higher temperatures, not attain-
able with commonly used cyano phases, will enable
you tomakemore injections with an
Rtx
®
-CLPesticides column.
Inmost laboratories, fast, efficient sample through-
put is important. In analyses of organophosphorus
pesticides, an Rtx
®
-CLPesticides column is an
important part of attaining—andmaintaining—this
goal.
Rtx
®
-CLPesticides columns are available in
convenient and economical kits
that include a deactivated guard column and
a connector. Refer to our general catalog, or
contact your local Restek representative.
Figure 1
AnRtx
®
-CLPesticides column provides sharp, fast resolution of organophosphorus pesticides.
Ordering Information
| Rtx
®
-CLPesticidesColumns (FusedSilica)
ID
df (µm)
temp. limits
10-Meter
15-Meter
20-Meter
30-Meter
60-Meter
0.10mm 0.10 -60 to 310/330°C 43101
0.18mm 0.18 -60 to 310/330°C 42101
42102
0.25mm 0.25 -60 to 320/340°C
11120
11123
11126
0.32mm 0.50 -60 to 320/340°C
11136
11139
0.53mm 0.50 -60 to 300/320°C
11137
11140
GC_EV00648
Column:
Rtx
®
-CLPesticides, 30m, 0.25mm ID, 0.25µm (cat.# 11123)
Sample:
Custom European StandardMix
call for details
1-bromo-2-nitrobenzene
cat.# 32279
4-chloro-3-nitrobenzotrifluoride
cat.# 32282
tributylphosphate
cat.# 32280
triphenylphosphate
cat.# 32281
Inj.:
1.0µL splitless (hold 0.4min.)
4mm double gooseneck inlet liner (cat.# 20785)
Inj. temp.:
250°C
Carrier gas:
helium, constant flow, 6 psi head pressure
Flow rate:
0.75mL/min.
Linear velocity:
28cm/sec.
Dead time:
1.82min. @ 80°C
Oven temp.:
80°C (hold 1.0min.) to 150°C@ 7°C/min. (no
hold) to 280°C@ 15°C/min. (hold 7min.)
Det.:
Agilent 5971AGC/MS
Transfer line temp.:
280°C
Scan range:
35–400 amu
Solvent Delay:
5min.
Tuning compound:
PFTBA
Ionization:
EI
Compound
Conc. on-column (ng)*
1. 4-chloro-3-nitrobenzotrifluoride (surr.) 100
2. methamidophos
50
3. dichlorvos
50
4. 1-bromo-2-nitrobenzene (surr.)
100
5. acephate
20
6. demeton-S-methyl
20
7. tributylphosphate (surr.)
100
8. omethoate
100
9. dimethoate
20
10. tolclofos-methyl
10
11. pirimiphosmethyl
10
Compound
Conc. on-column (ng)*
12. chlorpyrifos
10
13. malathion
20
14. quinalphos
10
15. tokuthion (prothiofos)
20
16. methidathion
20
17. profenfos
20
18. ethion
20
19. triphenylphosphate (surr.)
100
20. azinphos-methyl
40
21. pyrazophos
50
*Thismixwas prepared for FPD analyses. Peakswill be approximately equivalent in height with FPD
detection (0.32mm ID column).
