environmental
Applications
note
RestekCorporation • (800)356-1688 • (814)353-1300 •
#59559A
environmental
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Chlorine-substitutedphenoxyacetic acids, such as 2,4-D,MCPA,
and2,4,5-T [2,4-dichlorophenoxy acetic acid, (4-chloro-2-
methylphenoxy) aceticacid, and2,4,5-trichlorophenoxyacetic
acid respectively],were introducedas selectiveweedkillers in the
1940s.Due to theirgrowth-regulatingandherbicidal activities
against broadleafweeds, theyhave been commonlyused forweed
control on cereal crops, grasslands, and lawns. 2,4-D and2,4,5-T
alsowereusedas theprimarydefoliant agents inAgentOrange
during theVietnamWar. Today, chlorophenoxyherbicides still are
usedascommerciallyavailable lawnweedkillers.
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Chlorophenoxyherbicides are applied as either esters or salts,
which are easilymetabolizedbyplants. The esters areoil soluble,
but also canbe applied as emulsions inwater. The salts typically
are highly soluble inwater and are used as aqueous concentrates.
Because the chlorophenoxy herbicides are spread on top of the
soil or grass and then leach into the ground, there is great
potential for groundwater contamination. Chlorophenoxy
herbicides readilydegrade in the environment and formanyyears
were not considered an environmental or public concern.
However, potential hazards topublic health and environmental
quality led to the development ofUSEnvironmental Protection
Agency (EPA)methods for the analysis of these herbicides. US
EPAMethods 615 (municipal/industrial wastewater) and 8151
(solidwaste)were developed tomonitor chlorophenoxyherbi-
cides inenvironmental samples.
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Analysis of chlorophenoxy herbicides using gas chromatography
(GC) is difficult. In their free acid form, theseherbicides have
limitedvolatility and areprone to irreversible adsorption. To
overcome this problem, they aremost frequently analyzed as
methyl esters. Because theseherbicides canbe applied as several
different types of esters or as a salt, theymust first be converted
to the free acid form, thenderivatized intomethyl esters forGC
Figure 1
The Rtx
®
-CLPesticides and Rtx
®
-CLPesticides2 columns give good resolution for all 18
chlorophenoxy herbicides in a single injection.
30m,0.32mmID,0.50µm,Rtx
®
-CLPesticidescolumn(cat.#11139)and30m,0.32mmID,0.25µmRtx
®
-CLPesticides2column(cat.#11324).1.0µLdirect
injectionofchlorophenoxyherbicidesusingaUniliner
®
sleeve (cat.#20335),on-columnconcentration200-20,000pg/mL.
Oventemp.:
80°C(hold1min.) to300°C
@10°C/min. (hold10min.);
Inj. /det. temp.:
200°C/300°C;
Carriergas:
helium;
Inletpressure:
12.5psi set@80°C;
ECDsensitivity:
60kHz fusedsilica.
Rtx
®
-CLPesticides
Rtx
®
-CLPesticides2
1. dalapon
2. 3,5-dichlorobenzoic acid
3. 4-nitroanisole
4. DCAA
5. dicamba
6. MCPP
7. MCPA
8. dichloroprop
9. 2,4-D
10. pentachloroanisole
11. 2,4,5-TP
12. chloramben
13. 2,4,5-T
14. 2,4-DB
15. picloram
16. bentazon
17. dinoseb
18. DCPA
19. acifluoren
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OptimizingChlorophenoxyHerbicidesAnalysisUsingRtx
®
-CLPesticidesand
Rtx
®
-CLPesticides2Columns
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