Acrinathrin

All chemicals and solvents were of analytical quality grade. HPLC grade acetonitrile (MeCN) and methanol (MeOH) were purchased from LabScan (Dublin, Ireland). Insecticide standards, chlorpyrifos (98.3%), acrinathrin (99.7%), deltamethrin (99.9%) and ʎ-cyhalothrin (≥95.0%) were supplied by Sigma-Aldrich (St. Louis, MO, USA), Table 1. Buffered salts for QuEChERS extraction, including anhydrous magnesium sulphate (MgSO₄), sodium hydroxide (NaOH), sodium chloride (NaCl), trisodium citrate dihydrate (C₆H₅Na₃O₇·2H₂O) and disodium hydrogencitrate sesquihydrate (C₆H₈Na₂O₈), were also obtained from Sigma-Aldrich. dSPE clean-up tubes with primary secondary amine (PSA) and MgSO₄ were obtained from Waters (Milford, MA, USA). Phosphoric acid (PhA, ≥85%) was from BDH (Poole, UK), while formic acid (FA, ≥99%) was obtained from Merck (Darmstadt, Germany). Ultrapure water (H₂O) from a Milli-Q ultrapure water purification system (Millipore, Bedford, USA) was used for preparing the UHPLC mobile phase and other aqueous solutions. Filters of 13 mm with 0.22-µm PTFE membranes were used for filtration of the final extracts before UHPLC-PDA analysis.

All pesticide standards were obtained from Sigma-Aldrich (St. Louis, USA): coumaphos, acrinathrin, chlorfenvinphos, cypermethrin and DMPF with purity ≥ 98%; and chlorferon and DMF with 97% purity. Individual stock solutions (1000 mg/L) were prepared in acetonitrile and stored in amber vials at − 20 °C. Individual standard solutions and mixed standard solutions, used for the optimisation and calibration respectively, were prepared by an appropriate dilution of the stock standard solutions with acetonitrile.
Magnesium sulphate (MgSO₄), sodium acetate (NaAc), formic acid and ammonium formate were obtained from Sigma-Aldrich (Steinheim, Germany). PSA and C18 sorbents were purchased from Scharlab S.L (Barcelona, Spain), and Z-Sep from Agilent (Santa Clara, CA, USA). LiChrosolv acetonitrile was provided by Merck (Darmstadt, Germany). High purity water was obtained using a Milli-Q water purification system (Millipore, Milford, MA, USA).