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Methylation of Herbicides for Gas Chromatographic Determination

Published online by Cambridge University Press:  12 June 2017

E. A. Woolson  and
C. I. Harris
E. A. Woolson
Affiliation:
Crops Research Division, Agricultural Research Service, U. S. Department of Agriculture, Beltsville, Maryland
C. I. Harris
Affiliation:
Crops Research Division, Agricultural Research Service, U. S. Department of Agriculture, Beltsville, Maryland
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Abstract

Many acid herbicides must be methylated before analysis by gas-liquid chromatography. Several reagents were evaluated for the esterification of substituted acid herbicides. Esterification by the different methods was determined on 2,3,6-trichlorophenylacetic acid [fenac], 2,3,6-trichlorobenzoic acid [2,3,6-TBA], 4-amino-3,5,6-trichloropicolinic acid [picloram], 2-methoxy-3,6-dichlorobenzoic acid [dicamba], and 3,6-dichlorosalicylic acid, a possible metabolite of dicamba. The effect of substituent size and position is discussed in relation to esterification. The best methylating reagent for acid herbicides was diazomethane although it is toxic, explosive, and more costly than the other methods. BF3-methanol was equally as good when the compound was not sterically hindered. Water interfered with the esterification efficiency of all reagents. Diazomethane esterified the ammonium salt but not the sodium salt of the acids used.

Type
Research Article
Information
Weeds , Volume 15 , Issue 2 , April 1967 , pp. 168 - 170
Copyright
Copyright © 1967 Weed Science Society of America 

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References

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