The Separation And Preconcentration Of Nitrotriacetic Acid For Chromatographic Analysis In Complex Matrix

Nitrilotriacetic acid（NTA）and its salts were used as stabilizers and chelating agents in many industrial productions,such as papermaking,electroplating,and washing production.Because NTA was widely used and randomly discharged,it was widely detected in daily necessities,food and environmental waters（lake water,river water）.However,excessive exposal of NTA in human body could induce serious disease and cancers.Therefore,NTA was prohibited to use by some related regulations of China,the United States and the European Union.It was necessary to detect and control the concentration of NTA in industrial wastewater and other environmental waters.At present,the concentration level of NTA in environmental waters was low.The detection of NTA were also severely interfered by the co-existed ions and matrices.It was necessary to separate and preconcentrate the NTA before instrumental analysis.The adsorption material was essential for the sample pretreament.In recent years,anion exchange columns were commercialized and commonly applied.In addition,due to the large specific surface areas and strcture diversity of metal-organic framework materials,it had shown attractive performance in adsorption and separation.In this study,the sample pretreatment process was improved by using the anion exchange columns and the metal-organic framework materials.The trace level of NTA in industrial waste water and environmental waters were analyzed respectively.The details were as listed below:（1）We used anion exchange columns to preconcentrate of the NTA in industrial wastewater.The adsorbed NTA on the columns was simultaneouly eluted and derivated by the copper solution.With high performance liquid chromatography（HPLC）detection,the achieved limit of detection was 0.54 mg L^-1（S/N=3,n=7）,and the relative standard deviation was 0.40%(c=100 mg L^-1,n=9).Compared with the available methods,this method did not ues acid,alkalis and organic solvents for elution.It simplified the elution and derivatization steps,and reduced the sample pretreatment time.This method was convenient,timesaving and practical for detection of NTA.（2）The MIL-53（Al）was prepared,and its microscopic morphology and structure were characterized by the Fourier transform infrared spectroscopy,powder X-ray diffraction,scanning electron microscopy,pore size and Brunauer-Emmett-Teller analysis.It was tested for preconcentration of NTA in environmental waters in this study.The results showed that with simultaneouly derivatizated and eluted by Cu²⁺,and detected by HPLC,the determination of NTA in environmental water samples could be determined.The factors that affect the extraction efficiency,such as the extraction ultrasonic time,the p H of the water sample,the concentration of eluent and the volume of eluent were optimized.The interference effects of the co-existed metal ions were studied.The linear range of this method was 100-10000μg L^-1,the linear correlation coefficient（R²）was 0.9993,the limit of detection was 31.92μg L^-1（S/N=3,n=7）,and the relative standard peviation was 3.70%(c=500μg L^-1,n=9).With using MIL-53（Al）for preconcentration,the detection of NTA detection in seawater,domestic sewage,and industrial wastewater were achieved with recoveries in a range of 90.2%-91.1%,which indicated the method would be a simple,efficient,fast and sensitive for NTA detection.