WWRC 94-22
Solid-Phase Extraction of Dicamba and Picloram from Water and Soil Samples for HPLC Analysis
Abstract
Methods are presented for the analysis of two commonly used herbicides, dicamba and picloram, in
water and soil samples. The methods utilize solid-phase extraction (SPE) and high-performance
liquid chromatography (HPLC). For separation and concentration of the herbicides, two types of
SPE cartridges were used - aminopropyl (NH2) weak anion exchange adsorbent for
dicamba and octadecyl (C18) strong polar adsorbent for picloram. Detection limits for
HPLC analysis of dicamba were 1 ppb for water and 10 ppb for soil samples. Recovery experiments for
dicamba indicated 90-99% recovery for the concentration range 10-60 ppb in water samples and
83+/-6% recovery of 10 ppb of dicamba added to soil samples. Detection limits for picloram were
8 ppb for water and 10 ppb for soil samples. Recovery of picloram from water samples was between
85 and 96% for the 10-60 ppb concentration range and 88+/-6% recovery of 10 ppb of picloram added
to soil samples. The recovery of standard solutions by different brand name SPE cartridges was also
tested. Differences in the efficiencies of various SPE cartridges were determined, not only among
manufacturers but also between lots. It is suggested that one brand name of SPE cartridge, all of
the same lot number, be used throughout a particular study and that no changes in manufacturers
and lots be made without adequate evaluation of the SPE cartridges for their ability to separate
and concentrate the pesticide of interest.
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