Determination Of Heavy Metal Elements In Ion Exchange Resins And Their Migration During Application

Ion exchange chromatography（IEC）is a separation and purification technology based on the difference of charge between the chromatographic mediums and the separated objects as well as the difference of charge.It has been widely used in food,medicine and other fields.Ion exchange agents mainly include inorganic exchange agents and organic exchange agents,organic exchange agents are also called ion exchange resins.Heavy metal elements,organic carbon compounds and other harmful substances may be brought in ion exchange resins in the process of production,storage and transportation.When the resins come into contact with food and drugs,it will cause the contamination of products and other safety problems.Therefore,the establishment of an accurate detection method for heavy metal elements in ion exchange resins is of great significance for the safe application of resins in food,medicine and other fields.The study established a method for the determination of six heavy metal elements including lead,cadmium,mercury,manganese,nickel,copper and arsenic in ion-exchange resins by microwave digestion-inductively coupled plasma mass spectrometry（ICP-MS）,and explored the migration of heavy metal elements in the application process based on actual purification cases.The specific research results are as follows:（1）The determination method of cadmium,mercury,lead,manganese,nickel,copper and arsenic in ion exchange resins by microwave digestion-inductively coupled plasma mass spectrometry was established.The samples were pretreated with concentrated nitric acid digestion system and analyzed by inductively coupled plasma mass spectrometry after constant volume dilution.The results show that the linear correlation coefficients（R²）of the method are above 0.999,the RSDs are 0.12%～4.52%（n=6）,the detection limits are 0.002～0.005 mg·kg^-1,and the adding standard recoveries are 82%～109%.All of this meet the requirements of GB/T27417-2017 in appendix.The method was used to analyze 13 different types of resin samples,and the detailed information of heavy metal elements was obtained.The heavy metal elements of resins were compared and analyzed according to GB/T 2024395-2009 and GB 1886.300-2018.（2）A new method for purification of lysozyme from egg white by CM cationic resin was established.The unit enzyme activity was measured by turbidimetric assay.Finally,lysozyme is purified with a purity of 94.5%.The unit enzyme activity of the sample is 126000 U·mg^-1,which is six times higher than original data.In the experiment of purification of CSFV E2protein,TED chromatography was used to purify it.Finally,the purity of CSFV E2 protein is about 90%.During the purification of lysozyme,the proportion of As dissolved in each purification step was investigated by sampling and analysis at different purification stages.The results show that the proportion of permeation fluid is 13.2%,the proportion of rebalancing fluid is 29.8%,the proportion of eluting protein is 30.0%,the proportion of target protein solution is 18.5%,and the proportion of other solutions is 8.5%.Samples were taken and analyzed at different stages of CSFV E2 protein purification process,and the proportion of Ni dissolved in different purification steps was investigated.The results show that the proportion of initial equilibrium stage is 10.9%,the proportion of rebalancing solution is 55.8%,the proportion of target protein solution is 31.6%,and the proportion of other solutions is 1.8%.（3）In the experiment of exploring the migration of heavy metal elements in the resins,the dissolution rules and influencing factors were explored by simulating the static and dynamic conditions of the resins.The use of resins in the practical purification processes were simulated to explore the proportions of heavy metal elements dissolved in different purification steps.The results show that under static conditions,the final dissolution amount of heavy metal elements can be increased by increasing temperature appropriately.Under dynamic conditions,for CM resin,appropriately increasing the flow rate can shorten the equilibrium time of heavy metal elements dissolution,but the final dissolution amount is not affected by the flow rate.However,for TED resin,the amount of heavy metal elements dissolve more at low flow rates,and the flow rate has little relationship with the dynamic dissolution equilibrium time.