Cr(Ⅲ)binding Phage Screened From Phage Displayed Peptide Library For The Separation And Preconcentration Of Cr(Ⅲ)

In this study,we first prepared immobilized metal resins using Ni-NTA affinity resins for the interaction with NEB heptapeptide phage library.By several rounds of positive biopanning against target Cr(III)and negative biopanning against foreign metal ions,phages which can bind with foreign metal ions were eliminated for the guarantee of selectivity,while phages which only bind with Cr(III)were kept and eluted by 0.5 M EDTA from Cr(III)-NTA resins.After randomly selecting a certain amount of phage clones and ELISA affinity testing,the Cr(III)binding peptide with best binding affinity was selected and its amino sequence was also analyzed.The obtained Cr(III)binding phage was immobilized on microbeads cytopore through electrostatic interaction for Cr(III)preconcentration and chromium speciation:Cr(III)was retained on the immobilized Cr(III)binding phages and eluted by diluted nitric acid.At pH 7.0,extra Cr(VI)which possess possible interferences to the preconcentration of Cr(III)was first removed by cytopore beads.Cr(III)preconcentration was achieved by retention on the immobilized Cr(III)binding phage and elution by 0.1 M HNO3.The concentration of Cr(III)was determined by ICP-MS,and the concentration of Cr(VI)was calculated by subtraction of the concentration difference of total Cr and Cr(III).With a sample volume of 4000μL and an elution volume of 400 μL,accurate determination of Cr(III)in the range of 0.05-0.50 μg L-1 and an enrichment factor of 7.1 can be achieved,along with a limit of detection of 15 ng L-1(3σ,n = 7)and a RSD of 3.6%(0.25 μgL-1,n=7).The method was used for the determination of chromium in a certified reference material of reverine water(GBW08608)and fair agreement was achieved between the certified and the found value of chromium concentration.The procedure was further demonstrated for the speciation of chromium in tap water and snow water samples,and satisfactory spiking recoveries were obtained.