Sample Container and Storage Temperature for Paclobutrazol Monitoring in Irrigation Water

摘要

Padobutrazol is a plant growth retardant commonly used on greenhouse crops. Residues from padobutrazol applications can accumulate in recirculated irrigation water. Given that paclobutrazol has a long half-life and potential biological activity in parts per billion concentrations, it would be desirable to measure padobutrazol concentration in captured irrigation supplies. However, there are no standard protocols for collecting this type of sample. The objective of this research was to determine if sample container material or storage temperature affect padobutrazol stability over time. In two experiments, padobutrazol was mixed in concentrations ranging from 0.04 to 0.2 mg.L-1 and stored in polyethylene, clear glass, or amber glass containers at temperatures of either 4 or 20 degrees C. Padobutrazol concentration was measured at 3, 14, and 30 days after the start of each experiment. Across the two experiments, there were no consistent trends in reduction of padobutrazol concentration with respect to container material or storage temperature. In the first experiment, there was an average of 5% reduction across all treatments from day 0 to 30, whereas in the second experiment, concentration did not decrease over the 30-day time period. These data suggest that padobutrazol is stable in collected water samples for at least 30 days, and that either glass or polyethylene containers are suitable for collecting greenhouse water samples for analysis of padobutrazol concentration. A minimum volume of 100 mL was determined to be the optimum to analyze water samples with diverse padobutrazol concentrations.