The Determination of Picloram Residues in Soil Using Gas Chromotography

Abstract

A chromatographic procedure for detecting 4-amino-3,5,6-tricholorpicolinic acid (picloram) residue to a sensitivity of approximately 0.05 ppm in soils is described. Picloram is extracted from soil as the free acid and methylated with boron trifluride-methanol reagent. Data indicate that the amount of herbicide which actually reaches the soil may only be 10% of that applied to dense stands of oak. Rainfall was an important factor in determining the movement and persistence of picloram. Picloram was detected to a depth of 24 in within 6 weeks after application. No detectable residues were found in the upper 24 in of soil after one year with rates as high as 8 lb/A.