title: Use of ion-pairing reagent for improving iodine speciation analysis in seaweed by pressure-driven capillary electrophoresis and ultraviolet detection.
abstract: This study achieved resolution improvement for iodine speciation in the presence of an ion-pairing reagent by a pressure-driven capillary electrophoresis (CE) system. Addition of 0.01mM tetrabutyl ammonium hydroxide (TBAH) as the ion-pairing reagent into the electrophoretic buffer resulted in the complete separation of four iodine species (I(-), IO3(-), mono-iodothyrosine-MIT and di-iodothyrosine-DIT), because of the electrostatic interaction between TBAH and the negatively charged analytes. A +16kV separation voltage was applied along the separation capillary (50μm i.d., 80cm total and 60cm effective) with the inlet grounded. The detection wavelength was fixed at 210nm, and the pressure-driven flow rate was set at 0.12mLmin(-1) with an injected volume of 2μL. The optimal electrolyte consisted of 2mM borate, 2mM TBAH and 80% methanol with pH adjusted to 8.5. Baseline separation of iodine species was achieved within 7min. The detection limits for I(-), IO3(-), MIT and DIT were 0.052, 0.040, 0.032 and 0.025mgL(-1), respectively. The relative standard deviations of peak heights and areas were all below 3% for 5mgL(-1) and 5% for 1mgL(-1). Application of the proposed method was demonstrated by speciation analysis of iodine in two seaweed samples. The developed method offered satisfactory recoveries in the 91-99% range and good precisions (<5%). Good agreement between the determined values by the proposed CE method and the HPLC-ICP-MS method was also obtained. All results proved its great potential in routine analysis of iodine speciation in environmental, food and biological samples.
authors.affiliation: College of Material Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 310036, China.
authors.forename: Jiannan
authors.initials: J
authors.lastname: Sun
authors.affiliation: College of Material Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 310036, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Wang
authors.affiliation: College of Material Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 310036, China. Electronic address: hycheng@hznu.edu.cn.
authors.forename: Heyong
authors.initials: H
authors.lastname: Cheng
authors.affiliation: College of Material Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 310036, China; Qianjiang College, Hangzhou Normal University, Hangzhou 310036, China. Electronic address: jinhua6903@163.com.
authors.forename: Jinhua
authors.initials: J
authors.lastname: Liu
authors.affiliation: College of Material Chemistry and Chemical Engineering, Hangzhou Normal University, Hangzhou 310036, China.
authors.forename: Yuanchao
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Institute of Analytical and Applied Chemistry, Department of Chemistry, Zhejiang University, Hangzhou 310027, China.
authors.forename: Zigang
authors.initials: Z
authors.lastname: Xu
mesh_terms: D002021:Buffers; D002623:Chemistry Techniques, Analytical / Q000379:methods*; D004573:Electrolytes; D019075:Electrophoresis, Capillary; D007454:Iodides / Q000737:chemistry; D007455:Iodine / Q000032:analysis / Q000737:chemistry*; D012624:Seaweed / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D002021:Buffers; D004573:Electrolytes; D007454:Iodides; D007455:Iodine
keywords: Capillary electrophoresis; Iodine speciation; Ion-pairing; Seaweed