| Adrenaline(Ad),which belongs to catecholamines,is a very important neurotransmitter.Ad is synthesized in adrenal medullary chromium cell,both the absence and excess of Ad can results in some diseases.Ascorbic acid(AA)is an essential vitamin for the human body,but we have to obtain it from food because that the body cannot synthesis it.Therefore,AA is used for the prevention and adjuvant treatment of some diseases.Ad and AA can be determined or tested by electrochemical method because both of them have electrochemical activity.In recent years,people have fabricated a variety of modified electrodes or electrochemical sensors to detect them.In the past 20 years,due to their unique and good properties,room temperature ionic liquids have prompted a significant amount of research interest and used widely in materials,biocatalysis,electrochemistry and separation etc.In electrochemical applications,ionic liquids have been fabricated all kinds of modified electrode and electrochemical sensor for the detection,performance studies or electrochemical reactions of Ad and AA.In addition,some toxic organic solvents have been gradually replaced by ionic liquids for the separation of Ad and AA and other biological active substances.These applications are closely related with the interactions between ionic liquids and the two electroactive materials at mixtures.Therefore,it is a very important and urgent problem how to make a systematic study on the interaction mechanism of ionic liquids with Ad and AA,which can provide theoretical basis for the research and application of catecholamines and vitamins in the field of pharmaceutical chemistry and life science,and explain the reason why ionic liquids can be used for their detection and that some special properties of ionic liquids which demonstrated in detection process from a microeconomic view,provide theory and design support for the application of ionic liquids on electroactive material detection.The interactions of the adrenaline hydrochloride(AH)with water,imidazolium ionic liquids with AH/AA have been studied,and the effects of the structure,the types,and the concentrations of ionic liquids,and the pH of the solution on the interactions between above systems were discussed in this paper,the results are summarized as following:1.The interactions of AH with water have been investigated by nuclear magnetic resonance(1HNMR)and electrochemical cyclic voltammetry(CV).The results indicated that there is not only the formation of intermolecular hydrogen bonding between AH and H2O but also the formation of π-π stacking of benzene ring of AH at high concentration.In addition,the pH value of the solution has mainly effect the electrochemical behavior of adrenaline and has no effect on the interactions.The results provide foundation for studying the interactions of imidazolium ionic liquids with AH in aqueous.2.The interactions of AH with nine imidazolium ionic liquids([C4mim][BF4],[C6mim][BF4],[C8mim][BF4],[C4mim][Cl],[C4mim][Br],[C6mim][Br],[C8mim][Br],[C10mim][Br],[C12mim][Br])have been investigated by 1H NMR and CV in aqueous solution.According to the changes of the oxidation and reduction potentials and currents in cyclic voltammograms and the 1H NMR spectra of AH,it was found that the π-π stacking exist between the imidazole rings of ionic liquids and the benzene rings of AH,which lead to an easier oxidation of AH,and the electrochemical activity that of the phenolic hydroxyl groups on the benzene ring of AH enhanced.Moreover,the length of alkyl chain on the cations and the type of the anions of the ionic liquids have different degree effect on the n-n stacking,but the pH value of the solution has no effect on the interactions.3.The interactions of AA with nine imidazolium ionic liquids([C4mim][BF4],[C6min][BF4],[C8mim][BF4],[C4mim][Cl],[C4mim][Br],[C6mim][Br],[C8mim][Br],[C10mim][Br],[C12mim][Br])have been investigated by 1H NMR and CV in aqueous solution.According to the changes of the oxidation and reduction potentials and currents of cyclic voltammograms of AA and the 1H NMR spectra of imidazolium ionic liquids in the mixed system,it was found that the hydrogen bonding interactions formed between AA and ionic liquids,which results in a more difficult electrochemistry oxidation process of AA,and the hydrogen atoms on the enediol of AA are difficult to donate protons.The cations and anions of the ionic liquids have different degree effect on the hydrogen bonding interactions,but the pH value of the solution has no effect on the interactions. |
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