Instruments and Consumables
Instrument and consumer electronic balance (model: XS 225A-SCS, manufacturer: Shanghai Anpu Technology Co., Ltd.), vortex oscillator (model: genius3, manufacturer: Changzhou Guohua Electric Appliance Co., Ltd.), high-speed desktop centrifuge (model: CF16RX Ⅱ, manufacturer: Shanghai Yidian Scientific Instrument Co., Ltd.), ultrasonic cleaner (model: SB-100B, manufacturer: Suzhou Antai Air Technology Co., Ltd.), Gas chromatography-mass spectrometry (model: Agilent 7890/5975C, Shimadzu (Shanghai) Technology Co., Ltd.), high-resolution transmission electron microscope (TEM, model: Talos F200x, manufacturer: Philips Fei, the Netherlands), Vibrating sample magnetometer (VSM, model: lake shore 7410, manufacturer: Antai Technology Co., Ltd.).
Reagents
Mesoporous carbon (purity: 98.2%, outer diameter: 10-50 nm, inner diameter: 5-10 nm, length: 20-40 µm, specific surface area:>150 m2/g, Beijing Kechuang haiguang Co., Ltd.), N-propyl ethylenediamine (PSA, purity: 97%, Shenzhen nanopore Co., Ltd.), octadecylsilane bonded silica gel (C18, purity: 99.6%, Ningbo Xinzhi Biotechnology Co., Ltd.). Acetone (purity: 99.6%, Xi'an Yonghong chemical raw material Co., Ltd.), N-hexane ( purity: 99.6%, Shenzhen shidejia Technology Co., Ltd.), acetonitrile ( purity: 99.8%, Gaobeidian longnianda Trading Co., Ltd.), divalent iron salt (FeCl2·4H2O) and trivalent iron salt (FeCl3·6H2O), ammonia (NH3·H2O) (purity: 99.6%, Beijing Zhenxiang Technology Co., Ltd.), Octadecane amine (purity: 98.8%, Gaobeidian longnianda Trading Co., Ltd.), potassium permanganate (purity: 99.1%, Beijing Zhenxiang Technology Co., Ltd.), ethanol (purity: 98.9%, Beijing Zhenxiang Technology Co., Ltd.), secondary distilled water. Sixteen organophosphorus pesticide reference materials, Chlorpyrifos, Methamidophos, Hydrocarbophos, Triazophos, Propylphos, Dimethoate, Dichlorvos, Omethoate, Propylphos, Parathion, Malathion, Metoclophos, Acephate, Fenitrophos, Phoxim, Monocrotophos and other organophosphorus pesticide criteria (the purity of the above standards is >99%, and they are all purchased from Beijing Haibin Hongmeng reference material technology Co., Ltd.).
Preparation of magnetic Fe3O4 nanoparticles
In this test, magnetic Fe3O4 nanoparticles were prepared by the chemical coprecipitation method. The specific test process is as follows: NH3·H2O was used as the precipitant, a certain amount of FeCl2·4H2O and FeCl3·6H2O was added to the beaker, and then 25% NH3·H2O was added to the cup. After stirring vigorously, the water bath is kept at a constant temperature, the mixed liquid gradually turns from orange-red to black, and then the reaction is stopped after stirring for 55 min. The mixture is separated under an external magnetic field, repeatedly washed with distilled water until the pH is neutral, the supernatant is removed, and dried in a vacuum at 70 ℃ for 18 h. after grinding, the final product magnetic Fe3O4 nanoparticles (MNPs) are obtained.
Synthesis of Octadecylamine functionalized mesoporous carbon composites
Weigh 100 mg of mesoporous carbon (SBA-15) into a 250 mL round bottom flask, add 100 mL of ethanol and sonicate for 30 min to completely dissolve it, then add 400 mg of octadecane amine, stir at 70 °C for 2 h, centrifuge at 6000 rap/min for 8 min, washed twice with distilled water, vacuum dry and standby.
Synthesis of functional mesoporous carbon magnetic carbon nanomaterials supported by magnetic Fe3O4 nanoparticles
Synthesis of magnetic Fe3O4 nanoparticles loaded with functionalized mesoporous carbon magnetic carbon nanocomposites this study synthesized magnetic Fe3O4 nanoparticles loaded with functionalized mesoporous carbon to form magnetic mesoporous nanocomposites. The specific synthesis process is as follows: 10 mL of magnetic nanoparticles with a concentration of 10 mg/mL are slowly added to the functionalized mesoporous carbon suspension and continuously stirred, followed by going in an oil bath at 70 °C for 8 h. finally, the magnet is placed next to the flask to collect the black product. The black product is washed three times with distilled water and then dried under vacuum at 80 °C for 4 h to obtain the final product (MNPs/ODA-SBA-15). The synthesis mechanism of the composite is shown in Fig. 1.
Sample pretreatment
Accurately weigh 20.00 g of homogeneous spinach sample into a 50 mL centrifuge tube with a plug, add 100 µL of chlorpyrifos standard stock solution with a concentration of 10.0 µg/mL, add 25 mL of acetonitrile solution, shake for 30 min, add 3 g of sodium chloride, shake well, centrifuge at 3500 rap/min for 5 min, take 10 mL of supernatant into a 25 mL centrifuge tube with a plug, add 40 mg of magnetic mesoporous nanocomposites, vortex for 5 min, and after extraction, place the magnet on the wall of the centrifuge tube to collect the magnetic adsorbent. Then add 10 ml of acetonitrile solution, desorb for 15 min, 1 g of sodium chloride and 4 g of magnesium sulfate, and shake for 1 min. Centrifuge at 10000 rap/min for 10 min, take the supernatant, and filter it through 0.22 µM filter membrane to obtain the sample to be tested.
Mass spectrometry conditions
Mass spectrometry column: model: CP SIL 24 CB (30 m×0.25 mm×0.25 µm), Column temperature: 150 ℃ (2 min) → 8 ℃/min → 240 ℃ (7 min), Vaporization temperature: 220 ℃, Detection temperature: 240 ℃, Nitrogen: 5.0 mL/min, Ion source temperature 280 ℃, Injection mode: no split injection, Injection volume: 1 µL. Suck the mixed standard solution and the sample purification solution into the gas chromatograph, record the chromatogram, determine the retention time qualitatively, and determine the peak area ratio of the sample and the standard sample quantitatively.