Introduction
Phenoxyacidherbicides, such as 2,4-D, dicamba, picloram, andSilvex, are used to
control agricultural and aquaticweeds. These compounds can be found in the acid
form, or as the salts or esters.Whilenot considered highly toxic, phenoxyacid
herbicides aremonitored in agricultural monitoringwells and drinkingwater
sources. Traditionally, these compounds have been analyzed by gas
chromatography (GC), for example byUSEPAMethod 8151. Tomake these
compounds amenable toGC, theymust first be converted to themethyl esters
using a derivatizingagent suchas diazomethane, a time-consumingprocedure.
An optimizedHPLCmethod for analyzing phenoxyacidherbicides using aC18
column and gradient procedurewas previously presented. In order to perform
confirmationanalysis, a second columnproducing retention time and elution order
changes is needed. A confirmation column has been developed that has a
different selectivity for the phenoxyacidherbicides than aC18 stationary phase
using the same gradient procedure.
A solid phase extraction (SPE)method has been verified toextract and
concentratewater samples up to 1L volume and to quantitatively recover at least
16 of the common underivatizedherbicides inTable 1. This simple sample
preparation stepprovides cleaner analytical samples and lower HPLC detection
limits, making this a suitable replacement for GC analysis.
