Determination Of Heavy Metals By ICP-MS Base On Covalent Organic Frameworks CTpBD Enrichment

Covalent organic frameworks(COFs),an exciting new type of crystalline porous organic materials,are ingeniously constructed with organic building units via strong covalent bonds.Covalent organic frameworks arepure organic polymer materials formed by small organic molecules through covalent bonds,featured with large specific surface area and uniform pore size distribution.COFs presents variety by different structural motifs and connection types,further,the various functional sites in the structural motifs facilitating many unique advantages in applications of gas storage,photoelectric,catalysisand other fields.Herein,the typical porous covalent organic frameworks CTpBD with superior chemical stability and large surface area were applied.In this paper,the new material CTpBD was used as sorbent for COF-filled on-line SPE column of heavy metals in samples by combining flow injection on-line preconcentration with ICP-MS.The synthesized CTpBD were also characterized with XRD,FT-IR,SEM,TEM and BET.The well-prepared and fully-characterized CTpBD COFs were filled in COF-filled on-line SPE column as novel and robust adsorbents for element analysis.The affecting factors in solid phase extraction efficiency,such as the amount of the fillers,pH and flow rate of sample,eluent acid concentration and volume were studied and optimized in this study.The results showed that 20 mg of filler could achieve the absorption of target trace elements,(Cr(?),Mn(?),Co(?),Ni(?),Cd(?),V(?),Cu(?),As(?),Mo(??))in the sample solution.The final result,pH was 5.0,the sample flow rate was 1.5 mL min-1,the elution concentration nitric acid was 0.7 mol L-1,and the elution volume was 2 mL.Under the optimized concentration conditions,the target trace elements got a wide linearity range at(0.05-50 ?g L-1).The detection limits of Cr(?),Mn(?),Co(?),Ni(?),Cd(?),V(?),Cu(?),As(?)and Mo(?)were 3.4,3.3,2.5,2.3,2.1,2.3,3.4,12.1and9.3 ng L-1 respectively.The relative standard deviations(RSD)of 1.2%-3.6%obtained via 11 parallel determinations at the sample concentration of 100 ng L-1 indicated excellent repeatability of the developed methods.In the cycle tests,more than 20 adsorption-elution cycles with stable SPE recoveries of the target metal ions,the results indicated that the column was stable.The method established in this work was also used to measure the Cr,Mn,Co,Ni,Cd,V,Cu,As and Mo in certified reference materials(GBW10044,GBW10012,GBW10047),and the results were also in accord with the national standards results.In addition,the enrichment and detection,recovery tests of rice,corn and carrot showed the recovery rate was between 82%and 109%.