Piperonyl butoxide

7-Ethoxycoumarin, 7-hydroxycoumarin, NADPH, and Piperonyl butoxide were obtained from Sigma-Aldrich (St Louis, MO, USA). Bovine serum albumin was purchased from Thermo Scientific (Meridian Rd., Rockford, IL 61101, USA).

The following commercial insecticides were utilized in the bioassays: abamectin, 18 g L⁻¹ emulsifiable concentrate (Agrimec, Hebei Veyong Biochemical Co., Ltd., Shijiazhuang, China); bifenthrin, 100 g L⁻¹ emulsifiable concentrate (Capture, Bayer Cropscience China Co., Ltd., Beijing, China); chlorpyrifos, 480 g L⁻¹ emulsifiable concentrate (Lorsban, Dow AgroScience, Beijing, China); flupyradifurone, 17% soluble concentrate (Sivanto, Bayer Cropscience China Co., Ltd., Beijing, China); imidacloprid, 100 g L⁻¹ suspension concentrate (Gaucho, Bayer Cropscience China Co., Ltd., Beijing, China), sulfoxaflor, 22% suspension concentrate (Transform, Dow AgroScience, Beijing, China); and thiamethoxam, 250 g L⁻¹ water dispersible granule (Actara, Syngenta Crop Protection Company, Shanghai, China). Triphenyl phosphate (TPP), diethyl maleate (DEM), and piperonyl butoxide (PBO), dimethyl sulfoxide (DMSO), and Triton X-100 were bought from Sigma Aldrich, Shanghai, China.

Unless stated otherwise all chemicals used were of analytical grade, or in the case of chromatographic solvents, gradient grade or ULC/MS grade (mass spectrometry). Bisphenol A (BPA, purity 95%) was provided by Fluka (Sigma-Aldrich, St. Louis, MO, United States; now belonging to Merck Group, Darmstadt, Germany). Dibutyl phthalate (DBP, purity > 99%), diethyl phthalate (DEP, purity 99.5%), and piperonyl butoxide (PB) of technical grade (purity 90%) were purchased from Sigma-Aldrich. 2,2′-Azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS, purity > 98%) was obtained from AppliChem (Darmstadt, Germany). All other chemicals were purchased from Merck, Sigma-Aldrich and Th. Geyer GmbH (Renningen, Germany).

Gossypol, 7.ethoxycoumarin, nicotinamide adenine dinucleotide phosphate (NADPH), piperonyl butoxide (PBO), 7-ethoxycoumarin, 7-hydroxycoumarin, Ethylenediaminetetraacetic acid (EDTA) and phenylmethylsulfonyl fluoride (PMSF) were bought from Sigma-Aldrich (St. Louis, MO, USA). Deltamethrin 25% EC (Chimerical formulation) was obtained from Bayer crop science (Hang Zhou, China). Triton X-100 was from Amresco. Dithiothreitol (DTT), glycerol, and Tris were bought from Beijing Solarbio Scientific and Technology Company Beijing, China. Bovine serum albumin was purchased from Beyotime Biotechnology, Jiangsu, China. All chemicals and solvents used were reagent grade.

Technical grade permethrin was purchased from Chem Services Inc. (West Chester, PA, USA). Etofenprox (99%, Pestanal^® analytical standard), piperonyl butoxide (PBO; 99%, Pestanal^® analytical standard), and diethyl maleate (DEM; >96%) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Ethanol (>99%) was purchased from Fisher Scientific (Hampton, NH, USA). All test compounds and synergists were initially diluted into >99% ethanol (Fisher Scientific) before being serially diluted to the desired concentration (all in ethanol).

Methyl benzoate (MB), Tween 20, and Tween 80 were purchased from Fisher Scientific (Waltham, MA, USA). Piperonyl butoxide (PBO), triphenyl phosphate (TPP), and diethyl maleate (DEM) were purchased from Sigma-Aldrich (St. Louis, MO, USA).
Formulated insecticides, imidacloprid (Advise^® 2FL), acephate (Bracket^®97), λ-cyhalothrin (Karate^®), and oxamyl (Vydate^®), were purchased from local agricultural chemical suppliers and kept in a refrigerator (6 ± 1 °C). These representative insecticides were used for preparations of binary mixtures with MB. Insecticide name, manufacturer, percentage of active ingredient (a.i.), spray treatment concentrations, field use (spray) concentrations of formulation, and mode of actions were listed in Table 1.

Ammonium format and dimethyl sulfoxide (DMSO) were purchased from Sigma-Aldrich (Buchs, Switzerland). Gradient grade methanol, water, formic acid (FoA, 98–100%), isopropyl alcohol, and acetonitrile were products of Merck (Darmstadt, Germany). Human blank blood, stabilised by citrate-phosphate-derivative with adenine, was obtained from the local blood donation centre.
Ivermectin and ritonavir as well as the internal standard Ivermectin-d₂ were purchased from Toronto Research Chemicals (Toronto, Canada). Rifampicin, ketoconazole, and piperonyl butoxide were obtained from Sigma-Aldrich.