Conclusions
Based on this study, HPLCanalysis of phenoxyacidherbicides after solid phase
extraction is a viable alternative to the gas chromatographic procedure. The
chromatographic separation of the herbicideswas optimized usinganUltra
AqueousC18 column, aC18 stationary phasewitha polar embeddedgroup, and
confirmed using anAllureBasix column, apropyl cyano stationary phase. These
phases have enhanced selectivity for the acidic compoundswhen analyzedat low
pH. ThisHPLC technique does not requirederivitizationof the acidic analytes, a
stepwhich requires experienced laboratory personnel and a significant
preparation time commitment for each sample.
In order tomeet the required detection limits, a solid phase extractionmethod
was developedwhich resulted in a 200-fold concentration of the analytes during
cleanup. TheSPEmethod, using a substituted divinylbenzenepackingmaterial,
showedexcellent recoveries for all 16 acidherbicides and 1 surrogate, evenwith
1 liter samples. The internal standard shows lower recoveries than the target
herbicides; other options for the internal standardwill beexplored. TheSPE
method allows for rapid and quantitative recovery of these herbicides in their free
acid form.
