SOLID-PHASE EXTRACTION OF DICAMBA AND PICLORAM FROM WATER AND SOIL SAMPLES FOR HPLC ANALYSIS

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 chromatograp hy (HPLC). For separation and concentration of the herbicides, two typ es of SPE cartridges were used-aminopropyl (NH2) weak anion exchange a dsorbent for dicamba and octadecyl (C-18) strong polar adsorbent for p icloram. Detection limits for HPLC analysis of dicamba were 1 ppb for water and 10 ppb for soil samples. Recovery experiments for dicamba in dicated 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 sam ples. Detection limits for picloram were 8 ppb for water and 10 ppb fo r 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. Diff erences in the efficiencies of various SPE cartridges were determined, not only among manufacturers but also between lots. It is suggested t hat one brand name of SPE cartridge, all of the same lot number, be us ed 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.