Study On The Determination Of Tetracycline Antibiotic Residues In Animal-derived Foods By Solid Phase Extraction-high Performance Liquid Chromatography Based On The Synergistic Effect Of Biochar

The misuse of tetracycline antibiotics in intensive farming has led to an increase in tetracycline residues in animal-derived foods,prompting extensive research efforts both domestically and internationally.The accuracy and sensitivity of detecting tetracycline residues depend on the performance of sample pretreatment materials.Biochar,a carbon material produced through the pyrolysis of biomass,has emerged as a promising,cost-effective,and environmentally friendly material for sample pretreatment due to its excellent adsorption properties.In this study,we investigated the potential of a mixed biochar composed of Chlorella and bamboo for the solid-phase extraction of four tetracyclines in animal-derived foods.Through the characterization of the surface properties and microstructure of the biochar,fitting of adsorption models,and design of multi-factor screening experiments,we examined the separation mechanism of tetracycline antibiotics using single and mixed biochar,and their separation patterns in solid-phase extraction.Our findings indicate that the mixed biochar consisting of Chlorella and bamboo exhibited high sensitivity,stability,and effectively separated the four tetracycline antibiotics.（1）Chlorella biochar was a laminated material with a non-porous structure,composed of polyvinyl pyridine units.In contrast,bamboo biochar was a porous material with both micro and mesoporous structures,with polystyrene units.Despite Chlorella biochar exhibiting a low adsorption capacity for the four tetracycline antibiotics(0.27～0.54 mg·g^-1),it possessed abundant surface oxygen-containing functional groups with strong polarity and ion-exchange capacity.As a result,Chlorella biochar demonstrated good retention of polar and charged tetracycline antibiotics（64.75%～87.77%）.On the other hand,the high specific surface area of bamboo biochar resulted in a high adsorption capacity for tetracycline antibiotics(17.24～44.76 mg·g^-1).Both homogeneous and heterogeneous adsorption sites existed on the surface of bamboo biochar,and the adsorption of the four tetracycline antibiotics occurred through monolayer and multilayer chemisorption.The mesoporous structure of bamboo biochar significantly influenced the adsorption diffusion rate.（2）This study investigated the problems of desorption hysteresis and limited active sites when using moso bamboo biochar and chlorella biochar,respectively,for solid-phase extraction of tetracycline antibiotics.To address these issues,we explored the use of chlorella/bamboo hybrid biochar as an adsorbent.Experimental results demonstrated that the hybrid biochar reached adsorption-desorption equilibrium faster and exhibited better affinity for tetracycline antibiotics,particularly in selectivity and competition tests.Multifactorial screening tests revealed that extraction efficiency using chlorella biochar was mainly influenced by flow rate and column length,whereas hybrid biochar solid-phase extraction relied on the synergistic effect of partitioning separation of chlorella biochar and adsorption separation mechanism of bamboo biochar.Under optimal mixed biochar solid-phase extraction conditions,a recovery rate of 94.30±3.55%for tetracycline was achieved.Furthermore,we developed a method for the simultaneous determination of four tetracyclines in animal-derived foods using hybrid biochar solid-phase extraction coupled with high-performance liquid chromatography.The method demonstrated high accuracy and sensitivity,with detection limits ranging from 0.188 to 0.391μg·kg^-1 and recoveries of 80.80%to 106.98%in recovery tests...