title: Quantification of amino acid ionic liquids using liquid chromatography-mass spectrometry.
abstract: Amino acid ionic liquids (AAILs) containing imidazolium cations and amino acid (AA) anions, were synthesized and applied as task-specific ionic liquids. A sensitive and fast liquid chromatography-mass spectrometry (LC-MS) method was established for the quantitative analysis of 20 AAILs. Using ion pairing-reversed phase liquid chromatography technique, heptafluorobutyric acid was used as ion-pairing reagent to increase the retention of AAILs. Based on the zwitterionity of amino acid, this method was proposed to determine both the cation and the anion of AAILs simultaneously. The limit of detection of this method is down to 1-15ng/mL and the analysis time is less than 15min. According to the analytical data of seven selected AAILs, we found that the content of amino acid anion is always lower than that of butyl methyl imidazolium cation in AAILs. Moreover, the molar ratio of imidazolium cation to amino acid anion is dependent on the chemical property of the amino acid. These results supplied useful information on the interaction of imidazolium cation with acidic, basic, neutral and non-polar amino acids in AAILs.
authors.affiliation: College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Tang
authors.forename: Kangkang
authors.initials: K
authors.lastname: Wu
authors.forename: Zhou
authors.initials: Z
authors.lastname: Nie
authors.forename: Li
authors.initials: L
authors.lastname: Ding
authors.forename: Qian
authors.initials: Q
authors.lastname: Liu
authors.forename: Jinbin
authors.initials: J
authors.lastname: Yuan
authors.forename: Manli
authors.initials: M
authors.lastname: Guo
authors.forename: Shouzhuo
authors.initials: S
authors.lastname: Yao
mesh_terms: D000596:Amino Acids / Q000032:analysis*; D000838:Anions / Q000032:analysis; D002412:Cations / Q000032:analysis; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D052578:Ionic Liquids / Q000032:analysis*; D013058:Mass Spectrometry / Q000379:methods*; D012680:Sensitivity and Specificity
chemical_list: D000596:Amino Acids; D000838:Anions; D002412:Cations; D052578:Ionic Liquids