MT 129 - Gas liquid chromatography of phenoxyalkanoic and other herbicides

 

Content Handbook F

 

Outline of method

The herbicides are precipitated from alkaline solution with hydrochloric acid, extracted with diethyl ether and converted to their methyl esters or ethers with either diazomethane or methanol + sulphuric acid. The esters of ethers are separated by gas liquid chromatography on a column of Chromosorb G (AW, DMCS) or Chromosorb W (AW, DMCS) coated with Apiezon L, and the active ingredient determined, preferably by flame-ionization detection, using an internal standard. Duplicate sample solutions are prepared by the method given in the monograph for the active ingredient. Two portions of each solution are methylated and duplicate chromatograms are prepared for each, i.e. a total of eight chromatograms from the sample.
For schematic flow sheet of methods of analysis see Fig. 38. For routine purposes only one portion of each solution need be used, i.e. a total of four chromatograms from the sample.

 

 

 Scope

The method provides a suitable basis for the determination of the active ingredient(s) in the technical material and in most formulations containing the ionic salts of bromoxynil, 2,4-D, 2,4-DB, dichlorprop, fenoprop, MCPA, MCPB, mecoprop, 2,4,5-T and 2,3,6-TBA.