Preparation Of Biochar-based Molecularly Imprinted Polymers From Carbaryl And Their Application In Grain Pretreatment

Carbaryl is a broad-spectrum insecticide widely used in agriculture.However,the extensive use of carbaryl has remained in the environment and food,which is harmful to human health and may lead to neurological disorders,organ damage,carcinogenesis,etc.It is a compound that needs to be evaluated regularly.The detection of carbaryl residues usually requires pre-treatment of samples.Solid phase extraction（SPE）is the main pre-treatment method.Conventional SPE columns have shortcomings such as low specificity,poor reusability and high price,and the establishment of sensitive and efficient pretreatment methods is essential for monitoring food quality and safeguarding public health.In this study,the molecularly imprinted polymer（A-SBC@MIP）was prepared on the surface of soybean shell biochar with the advantages of stability and selectivity by combining biochar and molecular imprinting technology,and the preparation method,morphological characteristics and adsorption performance of soybean shell biochar and A-SBC@MIP were discussed.A method for the detection of carbaryl residues in grain samples was developed.The main findings of the study are as follows.1.A-SBC was prepared by first pre-carbonizing soybean shell powder and then using KOH as activator.The good activation conditions were obtained by single-factor test with1:2（w:w）soybean shell biochar and KOH,activation temperature of 750℃ and activation time of 1.5 h.The adsorption rate of A-SBC on carbaryl under these conditions was 89.63%and the adsorption capacity was 113.28 mg·g^-1.By characterization,it was found that the surface depression and pore size of A-SBC increased after activation,and some organic functional groups were reduced.2.The adsorption of carbaryl by A-SBC was higher in the range of p H=2-9 and maximum at p H=5.5,the adsorption increased with temperature and the adsorption amount was maximum at ionic strength=0.01 mo L·L^-1.The adsorption of carbaryl by A-SBC was more consistent with the quasi-secondary kinetic model.The isothermal adsorption curves are more suitable for fitting with Langmuir equation,which shows that chemisorption is dominant,and the adsorption thermodynamic results indicate that the adsorption of carbaryl by A-SBC is dominated by hydrophobic interaction and is a spontaneous heat absorption reaction.3.Bio-based surface molecularly imprinted polymers（A-SBC@MIP）and non-imprinted polymers（A-SBC@NIP）were synthesized using A-SBC as the carrier,methacrylic acid（MAA）as the functional monomer,and carbaryl as the template molecule.The optimal preparation conditions for A-SBC@MIP were obtained by single-factor test as follows,A-SBC of 100 mg,functional monomer（MAA）of 8 mmo L,cross-linking agent of 20 mmo L,acetonitrile as the porogenic agent in the amount of 80m L,methanol and acetic acid mixture（9:1,v/v）as the eluent.Characterization results showed that A-SBC was successfully grafted with MAA and molecularly imprinted polymer was grown on the surface of A-SBC.Under the conditions of 0.1 mo L·L^-1 Na Cl and p H=5,the adsorption capacity of A-SBC@MIP for carbaryl was 8.58 mg·g^-1.The results of kinetic and isothermal adsorption of A-SBC@MIP showed that the adsorption amount and the adsorption time were positively correlated,and the adsorption rate was fast and then slow,mainly by chemisorption.A-SBC@MIP had a better affinity for carbaryl.In addition,A-SBC@MIP has better anti-disturbance ability and good regeneration.4.A solid phase extraction column（A-SBC@MIP-SPE）was prepared using A-SBC@MIP as the sorbent,and the extraction procedure was optimized by a single-factor test with the optimal conditions of 4 m L loading volume,methanol/acetic acid（8:2,v/v）as the eluent and 4 m L dosage.The LOD of the method was 2.88μg·L^-1 with good linearity in the range of 0.01-5.00 mg·L^-1（R²=0.994）.The recovery of grains spiked with carbaryl was tested and ranged from 93.74 to 101.17%.The results suggest that the developed A-SBC@MIP-SPE-HPLC-UV can be used as a specific and cost-effective method for the identification and determination of carbaryl in food samples.