DETERMINATIONS OF CLOPYRALID, PICLORAM, AND SILVER AT LOW CONCENTRATION IN SOILS BY CALCIUM HYDROXIDE-WATER EXTRACTION AND GAS-CHROMATOGRAPHY MEASUREMENT

Clopyralid (3,6-dichloropicolinic acid), picloram (4-amino-3,5,6-trich loropicolinic acid), and silver (2-(2,4,5-trichlorophenoxy)propionic a cid) at concentrations of 0.0100 mu g/g in 14 fortified Alberta soils were determined by calcium hydroxide-water extraction and gas chromato graphy measurement. Precision of analyses was 1-13%. The herbicide rec overies from the soils with two different fortification procedures wer e compared. The relationships between recoveries and soil components w ere examined and discussed. Results from fortified soils, which were e xtracted immediately following spiking of herbicides, indicated clopyr alid recovery of 95.2 +/- 6.7% and was independent of the organic matt er (0.4-5.3%), clay (3.6-44.2%), sand (16.5-94.1%), or iron (3908-22 4 55 mu g/g) content in the soil; However, picloram and silver recoverie s (58.0-97.8%) were dependent on soil properties with a significant ne gative trend for being affected by the organic matter content of the s oil. Their recoveries decreased with increasing organic matter content of the soil. Detection limits of 0.0025-0.0500 mu g/g were herbicide and soil dependent. Results from fortified soil slurries which were ex tracted after 2-14 days of drying indicated lower herbicide recoveries . The different recoveries from two fortification procedures were disc ussed in relation to herbicide solubilities, soil-to-water partition c oefficients, sorption/desorption, and possible degradation.