Application Of Functionalized Magnetic Covalent Organic Polymers In The Analysis Of Hippuric Acid And Methyl Hippuric Acid

Toluene and xylene are commonly used toxic and harmful organic solvents.Monitoring the exposure level of toluene and xylene is beneficial to occupational health care.Hippuric acid(HA)and methyl hippuric acid(MHA)are biological indicators of toluene and xylene,so the concentration of HA and MHA in urine can reflect the exposure level of toluene and xylene.The matrix effect of sample and the low concentration of HA and MHA make the detection of HA and MHA difficult.It is very important to establish the pretreatment methods to enrich HA and MHA.Magnetic solid phase extraction(MSPE)is a branch of solid phase extraction(SPE)technology,which simplifies sample pretreatment process due to magnetic separation.Because of its advantages of simplicity,high efficiency and environmental protection,MSPE has been widely used in the analysis of various types of actual samples.Among them,functionalized magnetic materials,which directly affects the separation and enrichment properties of sample pretreatment,is a hot research field in MSPE technology.Covalent organic polymers(COPs)have many advantages such as large surface area,good stability,flexible functional design.It is a promising new material in separation enrichment.COPs composite provided more active sites to enhance the interaction between magnetic nanocomposites and analytes,increase specificity and improve sensitivity.The main work is to prepare functionalized magnetic covalent organic polymers and firstly apply it to the enrichment of hippuric acid and 4-methyl hippuric acid.(1)A magnetic covalent organic polymers composite functionalized by Zr⁴⁺(Fe₃O₄@COP-COOZr)was prepared,and Fe₃O₄@COP-COOZr were used as as material of MSPE for sample pretreatment.HA and 4-MHA were identified and concentrated by Fe₃O₄@COP-COOZr,based on chelation and electrostatic attraction,and then HA and 4-MHA were detected by HPLC.Under the best experimental conditions,a linear range of 5-500?g L^-1 for HA and 4-MHA shows good linearity.The correlation coefficient(R)of HA and 4-MHA were 0.9994 and 0.9967.The limit of detection(LOD)of HA and 4-MHA were 2.1 and 1.8?g L^-1.The intra-day and inter-day RSD(n=7)were less than 4.6%.The recoveries of HA and 4-MHA ranged from 97.2 to 104.1%,This method has good sensitivity and accuracy for HA and 4-MHA.(2)A magnetic covalent organic polymers composite(Fe₃O₄@SNW@Chitosan)functionalized by chitosan was prepared and used as material of MSPE for the determination of HA and 4-MHA in urine by HPLC.HA and 4-MHA were identified and concentrated by Fe₃O₄@SNW@Chitosan,based on hydrogen bond interactions and?-?interactions.Hydrophilic chitosan eliminates the interference of hydrophobic organic compounds in urine,including proteins,hormones,and other metabolites.Under the best experimental conditions,a linear range of 1-1000?g L^-1 shows good linearity.The correlation coefficient(R)of HA and 4-MHA were 0.9991 and 0.9987.The LOD of HA and 4-MHA were 0.3 and 0.2?g L^-1.The recoveries of HA and 4-MHA in urine samples ranged from 95.3 to 109.0%.This method provides a new idea for the detection of complex samples such as urine samples in the future.