Ionic Liquids Used For The Study And Application On The Speciation Analysis Of Heavy Metals Element

With the development of modern technology and living standard,much attention has been paid to a limit of the total amount of heavy metals.But more and more researches show that the total concentration of elements cannot directly give some information such as chemical properties,biological activity and toxicity,so the study of speciation analysis for elements is extremely necessary.Ionic liquid,as a kind of green reagents used for researches on the speciation analysis of heavy metals,has drawn much attention year by year.In this paper,some kinds of chelating agents assisting ionic liquid for the speciation analys is of chromium were explored and screened out with special selectivity.The purpose of this paper is to establish a novel pretreatment method for speciation analysis of chromium by chelating agent assisting ionic liquid and apply it to the actual samples,which has a certain practical significance for the speciation analysis of elements.The main contents of this paper are as follows:Firstly,the oxygen chelating agents assisting ionic liquid?[C₆MIM][PF₆]?for chromium speciation analysis had been researched.It showed that the results of extraction towards chromium by the oxygen chelating agents?1,2,3,4-butane tetracarboxylic acid?BTCA?,citric acid and tartaric acid?for assisting ionic liquid were not ideal.The common influence factors such as p H value,concentration of chelating agent and ultrasonic time were investigated.It was not obvious influence for the extraction efficiency,namely common factors almost couldn't improve the extraction efficiency.The extraction efficiencies of 1,2,3,4-Butane tetracarboxylic acid?BTCA?,citric acid and tartaric acid towards Cr?III?/ Cr?VI?were below 10%,which couldn't meet the requirements of extraction and also couldn't separate different valence chromium apart in the same sample.Secondly,the method of nitrogen chelating agents assisting ionic liquid?[C₆MIM][PF₆]?for chromium speciation analysis had also been studied.Results showed that this kind of chelating agents could extract trivalent chromium better than hexavalent chromium.The effects towards extraction system of chromium consisted of ionic liquid with rhodamine B and disodium-EDTA separately were not good enough,while the system with 1,10-Phenanthrolinemonohydrate and 8-hydroxyquinoline had the best extraction effects.The optimized extraction conditions for better system?1,10-Phenanthrolinemonohydrate and 8-hydroxyquinoline?were as follows,chelating agent concentration was 3%??/v?,the relevant p H value was 8 and 7,ultrasonic temperature was 35??45?respectively,ultrasonic time was 15 min,60 min respectively,the extractant concentration?nitric acid?was followed by 2 mol/L,1 mol/L respectively.The method detection limit was 0.044 0.054 ?g/L,the relative standard deviation RSD?%,n = 6?for the actual samples was 0.3% 6.7%,and the standard recovery rate was 93.5% 107.2%.The results showed that the method had the low detection limit,high precision and good accuracy.Thirdly,the pretreatment and enrichment methods were detected for the speciation analysis of chromium by the sulfur chelating agents as an assistant for ionic liquid.Through the optimization of extraction conditions,the extraction system composed of ionic liquid with rhodanine and dithizone respectively couldn't reach the aim of separation,and their extraction efficiency was quite low.The extraction system of ammonium pyrrolidinedithiocarbamate?APDC?and sodium diethyldithiocarbamatre?DDTC?could both separate different valence state of chromium and had been applied to determine a trace of chromium in real water samples.The optimized conditions were as follows: chelating agent concentration was 3%??/v?,the extraction temperature was 35?,ultrasonic time was 25 min,the extractant concentration?nitric acid?was 2 mol/L,the p H was 4,5 respectively.The method detection limit was 0.028 0.061?g/L,the relative standard deviation RSD?%,n = 6?used in actual water samples was 0.2% 4.2%,the standard recovery rate was 95.8% 108.2%,and the chromium content in actual water samples was in accordance with national standard GB3838-2002.The results showed that the method had low detection limit,simple operation and high sensitivity,etc.