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Title:   Author  item
                                            Altland, Jamesitem
                                            Morris, Leslieitem
                                            Boldt, Jenniferitem
                                            FISHER, PAUL - University Of Floridaitem
                                            RAUDALES, ROSA - University Of Connecticut
  Submitted to: HortTechnology
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 1/3/2015
                                    Publication  Date: 1/14/2016
                                    Publication URL: https://handle.nal.usda.gov/10113/5695368Citation: Altland, J.E., Morris, L.A., Boldt, J.K., Fisher, P., Raudales, R. 2016. Sample container and storage for paclobutrazol monitoring in irrigation water. HortTechnology. 25(6):769-773.Interpretive Summary: Paclobutrazol is a plant growth retardant commonly used on greenhouse crops.  Residues from paclobutrazol applications can accumulate in recirculated irrigation water.  Some crops are sensitive to very low concentrations of paclobutrazol.  It is important for greenhouse growers to periodically monitor their recirculated water to ensure paclobutrazol does not reach a high enough concentration to stunt irrigated crops.  To date, there is not guidance on how to collect water samples for paclobutrazol analysis.  The objective of this research was to determine the optimum container type, storage method, and storage time for collecting and submitted a water sample for paclobutrazol analysis.  We found that paclobutrazol stored in plastic, clear glass, or amber glass remained stable for 30 days whether it was stored at room temperature (23 C) or refrigerated (4 C).  Based on the volume of sample needed for analysis, we recommend that greenhouse growers collect a minimum of 100 mL of water in a clean plastic bottle for paclobutrazol analysis.  Water samples should be analyzed within 30 days.
                                Technical Abstract: Paclobutrazol is a plant growth retardant commonly used on greenhouse crops.  Residues from paclobutrazol 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 paclobutrazol 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 paclobutrazol stability over time.  In two experiments, paclobutrazol 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 °C.  Paclobutrazol 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 paclobutrazol 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 paclobutrazol 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 paclobutrazol concentration.  A minimum volume of 100 mL was determined to be the optimum to analyze water samples with diverse paclobutrazol concentrations.


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