▎ 摘　　要

NOVELTY - A three-dimensional graphene modified electrode for detecting phospholipids in crude oil is prepared by dispersing graphene oxide in water, ultrasonically dispersing, transferring into high pressure hydrothermal reaction kettle, oven reacting, cooling, freeze-drying solid, and taking three-dimensional graphene; putting screen printing electrode into beaker, adding sodium hydroxide solution, ultrasonically cleaning, taking lower electrode, washing by double distilled water, nitrogen drying, putting solid phase extraction into hydrochloric acid solution, ultrasonically cleaning, washing by double distilled water, nitrogen drying, washing electrode with absolute ethanol, drying by nitrogen, performing cyclic voltammetry curve scanning in phosphate buffered saline (PBS) buffer solution, dropping three-dimensional graphene solution on surface of screen printing electrode, and performing cyclic voltammetry (CV) curve scanning to modified SPE in PBS buffer solution. USE - The method is used for preparing three-dimensional graphene modified electrode for detecting phospholipids in crude oil. ADVANTAGE - The electrode has good selectivity and high sensitivity. DETAILED DESCRIPTION - A three-dimensional graphene modified electrode for detecting phospholipids in crude oil is prepared by: (A) dispersing 30-50 mg graphene oxide in 15-25 mL water, ultrasonically dispersing for 10 minutes to uniformly disperse, forming 2 mg/mL dispersion, transferring into high pressure hydrothermal reaction kettle, oven reacting at 160 degrees C for 12 hours, cooling to room temperature, freeze-drying solid, and taking three-dimensional graphene; (B) putting screen printing electrode into 100 ml beaker, adding 40-60 ml of 1 mmol/L sodium hydroxide solution in beaker, ultrasonically cleaning for 5 minutes, taking lower electrode, washing by double distilled water, drying by nitrogen, putting solid phase extraction into 40-60 mL of 1 mmol/L hydrochloric acid solution, ultrasonically cleaning for 5 minutes, washing by double distilled water, nitrogen drying, washing electrode with absolute ethanol, drying by nitrogen, performing cyclic voltammetry curve scanning in phosphate buffered saline (PBS) buffer solution at scanning voltage range of 0.2-0.6 V and scanning speed of 50 mV/second, dropping 4-6 mL three-dimensional graphene solution on surface of screen printing electrode, performing cyclic voltammetry (CV) curve scanning to modified SPE in PBS buffer solution, connecting modified solid phase extraction electrode of different materials to CHI660D electrochemical working station, inserting 50 mmol/L potassium ferricyanide solution, and performing electrochemical impedance spectroscopy test to modified screen printing electrode at frequency range of 10 6Hz to select best modified screen printing electrode material; (C) preparing PBS buffer solution containing 100 mg/L phosphatidylcholine (PC) as test base solution, dropping 4-8 mu L of 4 U horseradish peroxidase solution on solid phase extraction electrode surface modified by selected modified material, standing and drying at 4 degrees C, adding 5-10 mu L glutaraldehyde after electrode surface becomes thin, crosslinking at 37 degrees C for 30 minutes, washing electrode surface with PBS buffer solution, removing free horseradish peroxidase, adding 1-5 mu L chitosan/acetic acid solution on surface of enzyme-modified electrode, and standing and drying; (D) dropping 5-10 mu L of 1-8 U choline oxidase on modified electrode, dropping 5-10 mu L glutaraldehyde on electrode surface when electrode surface becomes thin, crosslinking to 37 degrees C for 30 minutes, washing electrode surface with PBS buffer solution, removing free choline oxidase on surface of electrode, nitrogen drying bio-enzyme screen printing electrode, storing in refrigerator at 4 degrees C, adding screen printing electrode to test solution with pH of 6.5-8.5 and thionine content of 1.0 mmol/L, adding 100 mu L of 3 mg/mL phospholipase D (PLD) solution, performing square wave voltammetry scanning at enrichment time of 30 seconds, voltage range of 0.5-0.5 V and scanning increment of 10 mV, recording peak current, and inspecting influence of choline oxidase concentration and pH on reduction peak current of screen printing electrode; (E) inserting bare screen printing electrode and biological enzyme screen printing electrode into PBS buffer solution and test solution containing 1 mmol/L thionine, respectively, and using cyclic voltammetry under condition that scanning speed is 50 mV/second and voltage range of 0.2-0.6 V to obtain stable cyclic voltammetry curve for testing electrochemical response of bio-enzyme screen printing electrode to PC; and (F) adding 40-60 mg PC into container filled with 90-110 mL first grade soybean oil, fully stirring to prepare soybean crude oil, dividing into 5 samples, diluting into PBS buffer solution with different concentrations, preparing 5 soybean crude oil sample with different PC content, adding 90-110 mu L of 3 mg/mL PLD solution, adding 1% Triton-X100 (RTM: polyethylene glycol tert octylphenyl ether) as emulsifier, stirring at 37 degrees C for 30 minutes, adding three-dimensional graphene modified electrode into 10-30 mL soybean oil under best condition, and using square wave voltammetry to measure reducing peak current to obtain PC content of 5 samples.