Study On Magnetic Biochars For The Enrichment And Determination Of Trace Organic Substance

Automatic-control analysis of environment contamination is crucial for us to realize smart environmental protection,while it relies greatly upon the development of advanced techniques in environmental analytical chemistry.In order to analyze trace pollutants in complex environmental samples,it is generally necessary to conduct the processes of separation and enrichment prior to instrument analysis.In this paper,three kinds of magnetic biochars were prepared by pyrolysis from corn straw,bamboo chip and pomelo peel,respectively.The preparation and extraction conditions were optimized by single factor variable method.Under optimal conditions,the magnetic biochars were evaluated for analyzing trace target analytes by magnetic solid phase extraction(MSPE)coupled with gas/liquid chromatography-mass spectrometry(GC/LC-MS).The main research conclusions are as follows:(1)The experimental conditions were optimized by single factor variable method.The results showed that the magnetic corn straw biochar prepared at 700℃ exhibited the best extraction performance through surface adsorption and π-π interactions.Under the optimal MSPE conditions,including the desorption solvent was ethyl acetate,extraction time was 35 min,and extraction time was 4 min.A method was developed for the determination of trace organophosphorus pesticides(OPPs)in the environmental water and soil by magnetic corn straw biochar based MSPE followed by GC-MS analysis.Under the optimal conditions,the linear range were found to be 0.50～50.00 μg/L,with coefficients of determination(R2)greater than 0.9911.The detection limits(LODs)were 0.02～0.19 μg/L,and the enrichment factors(EFs)were 51.8～210.2.The recoveries were in the range of 73.7-96.8%for the river water,pond water and soil samples,with great precision.(2)The experimental conditions were optimized by single factor variable method.The results showed that the magnetic bamboo chip biochar prepared at 400℃ exhibited the best extraction performance through surface adsorption,π-π interactions and hydrogen bonding.Under the optimal MSPE conditions,including desorption solvent was methanol,pH=7,extraction time was 20 min,and desorption volume was 200 μL.A method was established for the determination of trace fentanyl in serum and urine by magnetic bamboo chip biochar based MSPE followed by LC-MS analysis.Under the optimal conditions,the linear range were found to be 0.05～10.00 μg/L,with R2>0.9949.The LODs were 3.05～9.43 ng/L,and the EFs were 58.9～93.7.The recoveries were found to be in the range of 82.8～111.3%for urine and serum,with great precision.(3)The experimental conditions were optimized by single factor variable method.The results showed that the magnetic pomelo peel biochar prepared at 400 ℃ had better performance through surface adsorption,π-π interactions and hydrogen bonding.Under the optimal MSPE conditions,including the pH=7,extraction time was 20 min,desorption solvent was methanol,desorption volume was 200 μL and desorption time was 4 min.A method was developed for the determination of trace morphine,6-monoacetylmorphine and codeine in waste water samples by magnetic pomelo peel biochar based MSPE followed by LC-MS analysis.Under the optimal conditions,the linear range were found to be 0.05～10.00μg/L,with R2>0.9915.The LODs were 0.006～0.010 μg/L,and the EFs were 34.1～61.2.The recoveries were in the range of 71.8～80.6%for inlet and outlet waste waters from Haining,and the recoveries were in the range of 71.6～84.4%for inlet and outlet waste waters from Ningbo,with great precision.