Emr lipid

We purchased 186 pesticide reference material standards with purities greater than 95% from Sigma-Aldrich (Saint Louis, MO, USA) and Dr. Ehrenstorfer GmbH (Augsburg, Germany). MS-grade solvents, such as acetonitrile and ethyl acetate, were purchased from Merck Companies (Darmstadt, Germany); analytical grade acetic acid was obtained from Chengdu Kelong Chemical Reagent Company (Sichuan, China); analytical grade salts, such as sodium chloride (NaCl) and magnesium sulfate (MgSO₄), were from Shanghai GuoYao Chemical Reagents (Shanghai, China). Graphitized Carbon Black (GCB, 40 μm), MWCNTs, and Primary Secondary Amine (PSA, 40 μm) were purchased from ANPEL Laboratory Technologies Inc. (Shanghai, China). EMR-Lipid was obtained from Agilent Technologies, Inc. (Santa Clara, CA, USA). Ultra-pure water was obtained using a MilliQ UF-Plus system (Millipore, Darmstadt, Germany) with a resistivity of at least 18.2 MΩ.cm at 25 °C.

PAHs, PCBs, and their isotope-labeled internal standard were prepared by Dr. Ehrenstorfer GmbH (Augsburg, Germany). The purity of standards ranged from 95 to 99.8%. Solvents (acetonitrile, acetone, and isooctane) of HPLC grade, sodium chloride (NaCl), and anhydrous magnesium sulfate (MgSO₄) of analytical grade were obtained from Merck (Darmstadt, Germany). Also, primary secondary amine (PSA) was obtained from Agilent (Santa Clara, CA, USA), ammonium formate (NH₄O₂CH) was supplied by Fluka (Dresden, Germany), Z-Sep+ was supplied by Supelco (Bellefonte, PA, USA), and EMR-Lipid was purchased from Agilent (USA). The intermediate, stock, and working standard mixed solutions of PAHs and PCBs at 100 ng/mL, and internal standard solution at 10 μg/mL, were obtained in acetonitrile and isooctane, respectively, and kept at −18 °C with protection from light.