Norethisterone

Methanol (≥99.9%) and acetonitrile (≥99.9%) were purchased from Sigma-Aldrich (St. Louis, USA). All reagents used were of analytical grade. Anhydrous magnesium sulfate (MgSO₄), sodium chloride (NaCl), primary secondary amine (PSA), and alumina-N were purchased from Macklin Biochemical Co., Ltd. (Shanghai, China). High-purity (least 98% purity) analytical standards were used. Norethisterone, 17α-hydroxyprogesterone, D-methylnorethindrone, 17α-hydroxyprogesterone acetate, megestrol, medroxyprogesterone, chlorprogestone acetate, medroxyprogesterone acetate, melengestrol acetate, and progesterone were purchased from Sigma-Aldrich (St. Louis, USA).
Individual stock standard solutions (1000 mg/L) of each compound were prepared using Methanol and stored in the refrigerator at −20°C. The mixed standard solution was prepared by mixing the 10 individual stock standard solutions (100 μL for each) and diluting with Methanol to 10 mL in a volumetric flask, and the final concentration of each progestin was 10 mg/L. The mixed standard solutions prepared were stored at 4°C.
Acquity ultra-performance liquid chromatography (Waters USA); Synapt G2-Si quadrupole time-of-flight mass spectrometry (Waters USA); GR22GIII high-speed refrigerated centrifuge (HITACHI Japan); N-EVAPTM 112 nitrogen blowing apparatus (Organomation, USA); and KQ-500DE numerical control ultrasonic cleaner (Kunshan, China).

Natural flakes of graphite with an average particle diameter of 300 μm (99 wt% purity), sulfuric acid (98 wt%), hydrogen peroxide (30 wt%), phosphoric acid, potassium permanganate, hydrochloric acid (37 wt%), ethanol (100 wt%), ethyl ether, PEI (linear, Mw ≈ 50,000 g mol⁻¹), iron nanoparticles (FeNPs) [34 (link)], bisphenol A, progesterone and norethisterone were all purchased from Sigma Aldrich (Oakville, ON, Canada). All chemicals were used without further purification. Ultrapure water (18 MΩ∙cm) was used in all experiments.