Stability of herbicides and their degradation products on graphitized carbon black extraction cartridges used for large volumes of surface water

The stability of 18 herbicides (ten organonitrogens and eight phenylureas, including four degradation products), selected for the frequency of their detection in the environment, was evaluated under a variety of storage conditions. Large volumes of s ur- face water (4 L) were extracted using large-particle-size graphitized carbon black cartridges (Carbopack B 60-80 mesh). The effe cts of temperature, matrix type, drying and solvent-washing of cartridges on the recovery of these contaminants, after different stora ge periods, were studied and compared to the conservation of surface water in bottles. After two months, there was no significant di ffer- ence between the conserved surface water and the stored cartridges for the selected compounds. Cartridges kept at -20 °C were be t- ter than those stored at 4 °C and 20 °C. The type of matrix water selected, in this case St. Lawrence surface water, appears to hav e a minor effect on the recovery of the target pesticides after cartridge storage. No improvement was observed in the recovery of a ny of the chemicals when the cartridges were dried or washed and stored in a solvent. After immediate surface-water extraction, the mo st practical storage condition for the target herbicides was found to be storage on cartridges in the dark at - 20 °C, with no solven t dry- ing or washing of the Carbopack B material.