Quantification of methoprene aerosol deposition using reversed-phase high-performance liquid chromatography

Authors: Norton, Amie; Brabec, Daniel - Dan; Tilley, Michael - Mike; Yeater, Kathleen; Scheff, Deanna

Submitted to: Journal of Stored Products Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2023
Publication Date: 11/4/2022
Citation: Norton, A.E., Brabec, D.L., Tilley, M., Yeater, K.M., Scheff, D.S. 2022. Quantification of methoprene aerosol deposition using reversed-phase high-performance liquid chromatography. Journal of Stored Products Research. 99: Article 102039. https://doi.org/10.1016/j.jspr.2022.102039.
DOI: https://doi.org/10.1016/j.jspr.2022.102039

Interpretive Summary: Research studying aerosol spray as an effective method for insect control uses Aerodynamic Particle Sizers (APS) instrumentation to record airborne spray distribution and droplet size in test facilities. They are however limited in the particle size they can measure and thus the actual amount of active chemical depositing onto floors and other surfaces requires validation through other chemical methods. A chemical method assay was developed, using high performance liquid chromatography (HPLC), as a reference method which provided a method to calibrate APS units. This was used to adjust APS data and give more complete details on the total chemical being deposited. This method could be used by commercial pesticide applicators for spot testing of their application effectiveness using strategically placed petri dish collection points around a facility or work site before treatment. Treated dishes would be sent to a laboratory for analysis and provide data regarding their application effectiveness and provide additional confidence that the treatments were successful. Improving the use of aerosol insecticides will have a significant effect on reducing stored product insect populations and improve food and plant sanitation and safety.

Technical Abstract: Methoprene is an insect growth regulator (IGR), which acts on the juvenile stages of insects and is used as pest control method in food processing facilites. A chemical reference method was developed to quantitate aerosol deposition of methoprene using High-Performance Liquid Chromatography, HPLC. The method starts with placing 3.5 g flour in the Petri-dish (100mmx20mm) as an absorber and placing the Petri dish on the floor and in the facility by treated with pesticide aerosol. After treatment, the dishes are collected and analyzed with HPLC. The flour each dish was emptied into a 50 mL centrifuge tube along with 40 mL of methanol and mix time. The samples were then centrifuged and loaded on the HPLC. The HPLC method could detect Methoprene concentrations down to 0.15 ug/mL. In validation test, unknown samples matched the real spray times with a SE from 0.1-0.8. Historic methods used 120 min mixing time and 48 hour holding time. It was found that a mixing time of 30 min and 0 holding time was sufficient to obtain greater than 90% recovery. The objective of this study was to develop a standard chemical methodology to quantify the amount of methoprene insecticide deposited on floors and surfaces when applied from compressed cylinders as an aerosol insecticide. The HPLC method developed explored the impact of flour, mixing, holding, and processing times on methoprene recovery. The HPLC method developed in this study will provide pesticide applicators a method to accurately determine product deposition and provide an increased understanding of pesticide distributions throughout facilities.