Paraquat dichloride hydrate

For the exposure assays, bifenthrin (98% purity, CAS: 82657-04-3, part no. N-11203-100MG), chlorpyrifos (99.5% purity, CAS: 2921-88-2, part no. N-11459-250MG), dicloran (99.4% purity, CAS 99-30-9, part no. N-11678-250MG), myclobutanil (99.5% purity, CAS: 88671-89-0, part no. N-13261-100MG), paraquat dichloride hydrate (99.5% purity, CAS: 75365-73-0, part no. N-12818-500MG), penconazole (99.5% purity, CAS: 66246-88-6, part no. N-12822-100MG), and triadimefon (99.5% purity, CAS: 43121-43-3, part no. N-13636-500MG) were obtained from Chem Service (West Chester, PA, USA). Paraquat stock solution was prepared in deionized water and all other compounds were prepared in HPLC-grade methanol from Fisher Scientific (Waltham, MA, USA). All stock solutions were prepared by serial dilution, with a final solvent concentration of 0.1%.

Two 500 mL exposure solutions were collected from the middle concentrations of chlorpyrifos (acidified to myclobutanil, paraquat, penconazole, and triadimefon and three 100 mL samples were collected from bifenthrin at 5 PSU to confirm the chemical dosing methodology. The third concentration was selected for analysis since it reflected the range where we hypothesized LC₅₀ values would fall. Samples were shipped to Louisiana State University, Baton Rouge, LA, for analysis.
For analytical chemistry, bifenthrin (98% purity, CAS: 82657-04-3, part no. N-11203-100MG), chlorpyrifos (99.5% purity, CAS: 2921-88-2, part no. N-11459-250MG), myclobutanil (99.5% purity, CAS: 88671-89-0, part no. N-13261-100MG), paraquat dichloride hydrate (99.5% purity, CAS: 75365-73-0, part no. N-12818-500MG), penconazole (99.5% purity, CAS: 66246-88-6, part no. N-12822-100MG), and triadimefon (99.5% purity, CAS: 43121-43-3, part no. N-13636-500MG) were obtained from Chem Service (West Chester, PA, USA), and dicloran (96% purity, CAS: 99-30-9, part no. D67820-5G) was obtained from Sigma Aldrich (St. Louis, MO, USA). Solvents used include methanol, acetonitrile, water, and dichloromethane (chromatographic grade, VWR). Formic acid was 50% in water from Fluka Analytical (St. Gallen, Switzerland) and ammonium formate (97%) was from Fisher Scientific. All solvents and reagents used were analytical grade and were used without further purification.